llvm-6502/test/CodeGen/X86/block-placement.ll

1084 lines
29 KiB
LLVM
Raw Normal View History

; RUN: llc -mtriple=i686-linux < %s | FileCheck %s
declare void @error(i32 %i, i32 %a, i32 %b)
define i32 @test_ifchains(i32 %i, i32* %a, i32 %b) {
; Test a chain of ifs, where the block guarded by the if is error handling code
; that is not expected to run.
; CHECK: test_ifchains:
; CHECK: %entry
; CHECK: %else1
; CHECK: %else2
; CHECK: %else3
; CHECK: %else4
; CHECK: %exit
; CHECK: %then1
; CHECK: %then2
; CHECK: %then3
; CHECK: %then4
; CHECK: %then5
entry:
%gep1 = getelementptr i32* %a, i32 1
%val1 = load i32* %gep1
%cond1 = icmp ugt i32 %val1, 1
br i1 %cond1, label %then1, label %else1, !prof !0
then1:
call void @error(i32 %i, i32 1, i32 %b)
br label %else1
else1:
%gep2 = getelementptr i32* %a, i32 2
%val2 = load i32* %gep2
%cond2 = icmp ugt i32 %val2, 2
br i1 %cond2, label %then2, label %else2, !prof !0
then2:
call void @error(i32 %i, i32 1, i32 %b)
br label %else2
else2:
%gep3 = getelementptr i32* %a, i32 3
%val3 = load i32* %gep3
%cond3 = icmp ugt i32 %val3, 3
br i1 %cond3, label %then3, label %else3, !prof !0
then3:
call void @error(i32 %i, i32 1, i32 %b)
br label %else3
else3:
%gep4 = getelementptr i32* %a, i32 4
%val4 = load i32* %gep4
%cond4 = icmp ugt i32 %val4, 4
br i1 %cond4, label %then4, label %else4, !prof !0
then4:
call void @error(i32 %i, i32 1, i32 %b)
br label %else4
else4:
%gep5 = getelementptr i32* %a, i32 3
%val5 = load i32* %gep5
%cond5 = icmp ugt i32 %val5, 3
br i1 %cond5, label %then5, label %exit, !prof !0
then5:
call void @error(i32 %i, i32 1, i32 %b)
br label %exit
exit:
ret i32 %b
}
Rewrite #3 of machine block placement. This is based somewhat on the second algorithm, but only loosely. It is more heavily based on the last discussion I had with Andy. It continues to walk from the inner-most loop outward, but there is a key difference. With this algorithm we ensure that as we visit each loop, the entire loop is merged into a single chain. At the end, the entire function is treated as a "loop", and merged into a single chain. This chain forms the desired sequence of blocks within the function. Switching to a single algorithm removes my biggest problem with the previous approaches -- they had different behavior depending on which system triggered the layout. Now there is exactly one algorithm and one basis for the decision making. The other key difference is how the chain is formed. This is based heavily on the idea Andy mentioned of keeping a worklist of blocks that are viable layout successors based on the CFG. Having this set allows us to consistently select the best layout successor for each block. It is expensive though. The code here remains very rough. There is a lot that needs to be done to clean up the code, and to make the runtime cost of this pass much lower. Very much WIP, but this was a giant chunk of code and I'd rather folks see it sooner than later. Everything remains behind a flag of course. I've added a couple of tests to exercise the issues that this iteration was motivated by: loop structure preservation. I've also fixed one test that was exhibiting the broken behavior of the previous version. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144495 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-13 11:20:44 +00:00
define i32 @test_loop_cold_blocks(i32 %i, i32* %a) {
; Check that we sink cold loop blocks after the hot loop body.
; CHECK: test_loop_cold_blocks:
; CHECK: %entry
Rewrite how machine block placement handles loop rotation. This is a complex change that resulted from a great deal of experimentation with several different benchmarks. The one which proved the most useful is included as a test case, but I don't know that it captures all of the relevant changes, as I didn't have specific regression tests for each, they were more the result of reasoning about what the old algorithm would possibly do wrong. I'm also failing at the moment to craft more targeted regression tests for these changes, if anyone has ideas, it would be welcome. The first big thing broken with the old algorithm is the idea that we can take a basic block which has a loop-exiting successor and a looping successor and use the looping successor as the layout top in order to get that particular block to be the bottom of the loop after layout. This happens to work in many cases, but not in all. The second big thing broken was that we didn't try to select the exit which fell into the nearest enclosing loop (to which we exit at all). As a consequence, even if the rotation worked perfectly, it would result in one of two bad layouts. Either the bottom of the loop would get fallthrough, skipping across a nearer enclosing loop and thereby making it discontiguous, or it would be forced to take an explicit jump over the nearest enclosing loop to earch its successor. The point of the rotation is to get fallthrough, so we need it to fallthrough to the nearest loop it can. The fix to the first issue is to actually layout the loop from the loop header, and then rotate the loop such that the correct exiting edge can be a fallthrough edge. This is actually much easier than I anticipated because we can handle all the hard parts of finding a viable rotation before we do the layout. We just store that, and then rotate after layout is finished. No inner loops get split across the post-rotation backedge because we check for them when selecting the rotation. That fix exposed a latent problem with our exitting block selection -- we should allow the backedge to point into the middle of some inner-loop chain as there is no real penalty to it, the whole point is that it *won't* be a fallthrough edge. This may have blocked the rotation at all in some cases, I have no idea and no test case as I've never seen it in practice, it was just noticed by inspection. Finally, all of these fixes, and studying the loops they produce, highlighted another problem: in rotating loops like this, we sometimes fail to align the destination of these backwards jumping edges. Fix this by actually walking the backwards edges rather than relying on loopinfo. This fixes regressions on heapsort if block placement is enabled as well as lots of other cases where the previous logic would introduce an abundance of unnecessary branches into the execution. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154783 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-16 01:12:56 +00:00
; CHECK: %unlikely1
; CHECK: %unlikely2
Rewrite #3 of machine block placement. This is based somewhat on the second algorithm, but only loosely. It is more heavily based on the last discussion I had with Andy. It continues to walk from the inner-most loop outward, but there is a key difference. With this algorithm we ensure that as we visit each loop, the entire loop is merged into a single chain. At the end, the entire function is treated as a "loop", and merged into a single chain. This chain forms the desired sequence of blocks within the function. Switching to a single algorithm removes my biggest problem with the previous approaches -- they had different behavior depending on which system triggered the layout. Now there is exactly one algorithm and one basis for the decision making. The other key difference is how the chain is formed. This is based heavily on the idea Andy mentioned of keeping a worklist of blocks that are viable layout successors based on the CFG. Having this set allows us to consistently select the best layout successor for each block. It is expensive though. The code here remains very rough. There is a lot that needs to be done to clean up the code, and to make the runtime cost of this pass much lower. Very much WIP, but this was a giant chunk of code and I'd rather folks see it sooner than later. Everything remains behind a flag of course. I've added a couple of tests to exercise the issues that this iteration was motivated by: loop structure preservation. I've also fixed one test that was exhibiting the broken behavior of the previous version. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144495 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-13 11:20:44 +00:00
; CHECK: %body1
; CHECK: %body2
; CHECK: %body3
; CHECK: %exit
entry:
br label %body1
body1:
%iv = phi i32 [ 0, %entry ], [ %next, %body3 ]
%base = phi i32 [ 0, %entry ], [ %sum, %body3 ]
%unlikelycond1 = icmp slt i32 %base, 42
br i1 %unlikelycond1, label %unlikely1, label %body2, !prof !0
unlikely1:
call void @error(i32 %i, i32 1, i32 %base)
br label %body2
body2:
%unlikelycond2 = icmp sgt i32 %base, 21
br i1 %unlikelycond2, label %unlikely2, label %body3, !prof !0
unlikely2:
call void @error(i32 %i, i32 2, i32 %base)
br label %body3
body3:
%arrayidx = getelementptr inbounds i32* %a, i32 %iv
%0 = load i32* %arrayidx
%sum = add nsw i32 %0, %base
%next = add i32 %iv, 1
%exitcond = icmp eq i32 %next, %i
br i1 %exitcond, label %exit, label %body1
exit:
ret i32 %sum
}
!0 = metadata !{metadata !"branch_weights", i32 4, i32 64}
Rewrite #3 of machine block placement. This is based somewhat on the second algorithm, but only loosely. It is more heavily based on the last discussion I had with Andy. It continues to walk from the inner-most loop outward, but there is a key difference. With this algorithm we ensure that as we visit each loop, the entire loop is merged into a single chain. At the end, the entire function is treated as a "loop", and merged into a single chain. This chain forms the desired sequence of blocks within the function. Switching to a single algorithm removes my biggest problem with the previous approaches -- they had different behavior depending on which system triggered the layout. Now there is exactly one algorithm and one basis for the decision making. The other key difference is how the chain is formed. This is based heavily on the idea Andy mentioned of keeping a worklist of blocks that are viable layout successors based on the CFG. Having this set allows us to consistently select the best layout successor for each block. It is expensive though. The code here remains very rough. There is a lot that needs to be done to clean up the code, and to make the runtime cost of this pass much lower. Very much WIP, but this was a giant chunk of code and I'd rather folks see it sooner than later. Everything remains behind a flag of course. I've added a couple of tests to exercise the issues that this iteration was motivated by: loop structure preservation. I've also fixed one test that was exhibiting the broken behavior of the previous version. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144495 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-13 11:20:44 +00:00
define i32 @test_loop_early_exits(i32 %i, i32* %a) {
; Check that we sink early exit blocks out of loop bodies.
; CHECK: test_loop_early_exits:
; CHECK: %entry
; CHECK: %body1
Rewrite #3 of machine block placement. This is based somewhat on the second algorithm, but only loosely. It is more heavily based on the last discussion I had with Andy. It continues to walk from the inner-most loop outward, but there is a key difference. With this algorithm we ensure that as we visit each loop, the entire loop is merged into a single chain. At the end, the entire function is treated as a "loop", and merged into a single chain. This chain forms the desired sequence of blocks within the function. Switching to a single algorithm removes my biggest problem with the previous approaches -- they had different behavior depending on which system triggered the layout. Now there is exactly one algorithm and one basis for the decision making. The other key difference is how the chain is formed. This is based heavily on the idea Andy mentioned of keeping a worklist of blocks that are viable layout successors based on the CFG. Having this set allows us to consistently select the best layout successor for each block. It is expensive though. The code here remains very rough. There is a lot that needs to be done to clean up the code, and to make the runtime cost of this pass much lower. Very much WIP, but this was a giant chunk of code and I'd rather folks see it sooner than later. Everything remains behind a flag of course. I've added a couple of tests to exercise the issues that this iteration was motivated by: loop structure preservation. I've also fixed one test that was exhibiting the broken behavior of the previous version. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144495 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-13 11:20:44 +00:00
; CHECK: %body2
; CHECK: %body3
; CHECK: %body4
; CHECK: %exit
Rewrite #3 of machine block placement. This is based somewhat on the second algorithm, but only loosely. It is more heavily based on the last discussion I had with Andy. It continues to walk from the inner-most loop outward, but there is a key difference. With this algorithm we ensure that as we visit each loop, the entire loop is merged into a single chain. At the end, the entire function is treated as a "loop", and merged into a single chain. This chain forms the desired sequence of blocks within the function. Switching to a single algorithm removes my biggest problem with the previous approaches -- they had different behavior depending on which system triggered the layout. Now there is exactly one algorithm and one basis for the decision making. The other key difference is how the chain is formed. This is based heavily on the idea Andy mentioned of keeping a worklist of blocks that are viable layout successors based on the CFG. Having this set allows us to consistently select the best layout successor for each block. It is expensive though. The code here remains very rough. There is a lot that needs to be done to clean up the code, and to make the runtime cost of this pass much lower. Very much WIP, but this was a giant chunk of code and I'd rather folks see it sooner than later. Everything remains behind a flag of course. I've added a couple of tests to exercise the issues that this iteration was motivated by: loop structure preservation. I've also fixed one test that was exhibiting the broken behavior of the previous version. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144495 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-13 11:20:44 +00:00
; CHECK: %bail1
; CHECK: %bail2
; CHECK: %bail3
entry:
br label %body1
body1:
%iv = phi i32 [ 0, %entry ], [ %next, %body4 ]
%base = phi i32 [ 0, %entry ], [ %sum, %body4 ]
%bailcond1 = icmp eq i32 %base, 42
br i1 %bailcond1, label %bail1, label %body2
bail1:
ret i32 -1
body2:
%bailcond2 = icmp eq i32 %base, 43
br i1 %bailcond2, label %bail2, label %body3
bail2:
ret i32 -2
body3:
%bailcond3 = icmp eq i32 %base, 44
br i1 %bailcond3, label %bail3, label %body4
bail3:
ret i32 -3
body4:
%arrayidx = getelementptr inbounds i32* %a, i32 %iv
%0 = load i32* %arrayidx
%sum = add nsw i32 %0, %base
%next = add i32 %iv, 1
%exitcond = icmp eq i32 %next, %i
br i1 %exitcond, label %exit, label %body1
exit:
ret i32 %sum
}
define i32 @test_loop_rotate(i32 %i, i32* %a) {
; Check that we rotate conditional exits from the loop to the bottom of the
; loop, eliminating unconditional branches to the top.
; CHECK: test_loop_rotate:
; CHECK: %entry
; CHECK: %body1
; CHECK: %body0
; CHECK: %exit
entry:
br label %body0
body0:
%iv = phi i32 [ 0, %entry ], [ %next, %body1 ]
%base = phi i32 [ 0, %entry ], [ %sum, %body1 ]
%next = add i32 %iv, 1
%exitcond = icmp eq i32 %next, %i
br i1 %exitcond, label %exit, label %body1
body1:
%arrayidx = getelementptr inbounds i32* %a, i32 %iv
%0 = load i32* %arrayidx
%sum = add nsw i32 %0, %base
%bailcond1 = icmp eq i32 %sum, 42
br label %body0
exit:
ret i32 %base
}
define i32 @test_no_loop_rotate(i32 %i, i32* %a) {
; Check that we don't try to rotate a loop which is already laid out with
; fallthrough opportunities into the top and out of the bottom.
; CHECK: test_no_loop_rotate:
; CHECK: %entry
; CHECK: %body0
; CHECK: %body1
; CHECK: %exit
entry:
br label %body0
body0:
%iv = phi i32 [ 0, %entry ], [ %next, %body1 ]
%base = phi i32 [ 0, %entry ], [ %sum, %body1 ]
%arrayidx = getelementptr inbounds i32* %a, i32 %iv
%0 = load i32* %arrayidx
%sum = add nsw i32 %0, %base
%bailcond1 = icmp eq i32 %sum, 42
br i1 %bailcond1, label %exit, label %body1
body1:
%next = add i32 %iv, 1
%exitcond = icmp eq i32 %next, %i
br i1 %exitcond, label %exit, label %body0
exit:
ret i32 %base
}
define void @test_loop_rotate_reversed_blocks() {
; This test case (greatly reduced from an Olden bencmark) ensures that the loop
; rotate implementation doesn't assume that loops are laid out in a particular
; order. The first loop will get split into two basic blocks, with the loop
; header coming after the loop latch.
;
; CHECK: test_loop_rotate_reversed_blocks
; CHECK: %entry
; Look for a jump into the middle of the loop, and no branches mid-way.
; CHECK: jmp
; CHECK: %loop1
; CHECK-NOT: j{{\w*}} .LBB{{.*}}
; CHECK: %loop1
; CHECK: je
entry:
%cond1 = load volatile i1* undef
br i1 %cond1, label %loop2.preheader, label %loop1
loop1:
call i32 @f()
%cond2 = load volatile i1* undef
br i1 %cond2, label %loop2.preheader, label %loop1
loop2.preheader:
call i32 @f()
%cond3 = load volatile i1* undef
br i1 %cond3, label %exit, label %loop2
loop2:
call i32 @f()
%cond4 = load volatile i1* undef
br i1 %cond4, label %exit, label %loop2
exit:
ret void
}
define i32 @test_loop_align(i32 %i, i32* %a) {
; Check that we provide basic loop body alignment with the block placement
; pass.
; CHECK: test_loop_align:
; CHECK: %entry
; CHECK: .align [[ALIGN:[0-9]+]],
; CHECK-NEXT: %body
; CHECK: %exit
entry:
br label %body
body:
%iv = phi i32 [ 0, %entry ], [ %next, %body ]
%base = phi i32 [ 0, %entry ], [ %sum, %body ]
%arrayidx = getelementptr inbounds i32* %a, i32 %iv
%0 = load i32* %arrayidx
%sum = add nsw i32 %0, %base
%next = add i32 %iv, 1
%exitcond = icmp eq i32 %next, %i
br i1 %exitcond, label %exit, label %body
exit:
ret i32 %sum
}
define i32 @test_nested_loop_align(i32 %i, i32* %a, i32* %b) {
; Check that we provide nested loop body alignment.
; CHECK: test_nested_loop_align:
; CHECK: %entry
; CHECK: .align [[ALIGN]],
Rewrite #3 of machine block placement. This is based somewhat on the second algorithm, but only loosely. It is more heavily based on the last discussion I had with Andy. It continues to walk from the inner-most loop outward, but there is a key difference. With this algorithm we ensure that as we visit each loop, the entire loop is merged into a single chain. At the end, the entire function is treated as a "loop", and merged into a single chain. This chain forms the desired sequence of blocks within the function. Switching to a single algorithm removes my biggest problem with the previous approaches -- they had different behavior depending on which system triggered the layout. Now there is exactly one algorithm and one basis for the decision making. The other key difference is how the chain is formed. This is based heavily on the idea Andy mentioned of keeping a worklist of blocks that are viable layout successors based on the CFG. Having this set allows us to consistently select the best layout successor for each block. It is expensive though. The code here remains very rough. There is a lot that needs to be done to clean up the code, and to make the runtime cost of this pass much lower. Very much WIP, but this was a giant chunk of code and I'd rather folks see it sooner than later. Everything remains behind a flag of course. I've added a couple of tests to exercise the issues that this iteration was motivated by: loop structure preservation. I've also fixed one test that was exhibiting the broken behavior of the previous version. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144495 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-13 11:20:44 +00:00
; CHECK-NEXT: %loop.body.1
; CHECK: .align [[ALIGN]],
; CHECK-NEXT: %inner.loop.body
; CHECK-NOT: .align
; CHECK: %exit
entry:
br label %loop.body.1
loop.body.1:
%iv = phi i32 [ 0, %entry ], [ %next, %loop.body.2 ]
%arrayidx = getelementptr inbounds i32* %a, i32 %iv
%bidx = load i32* %arrayidx
br label %inner.loop.body
inner.loop.body:
%inner.iv = phi i32 [ 0, %loop.body.1 ], [ %inner.next, %inner.loop.body ]
%base = phi i32 [ 0, %loop.body.1 ], [ %sum, %inner.loop.body ]
%scaled_idx = mul i32 %bidx, %iv
%inner.arrayidx = getelementptr inbounds i32* %b, i32 %scaled_idx
%0 = load i32* %inner.arrayidx
%sum = add nsw i32 %0, %base
%inner.next = add i32 %iv, 1
%inner.exitcond = icmp eq i32 %inner.next, %i
br i1 %inner.exitcond, label %loop.body.2, label %inner.loop.body
loop.body.2:
%next = add i32 %iv, 1
%exitcond = icmp eq i32 %next, %i
br i1 %exitcond, label %exit, label %loop.body.1
exit:
ret i32 %sum
}
define void @unnatural_cfg1() {
; Test that we can handle a loop with an inner unnatural loop at the end of
; a function. This is a gross CFG reduced out of the single source GCC.
; CHECK: unnatural_cfg1
; CHECK: %entry
; CHECK: %loop.body1
; CHECK: %loop.body2
; CHECK: %loop.body3
entry:
br label %loop.header
loop.header:
br label %loop.body1
loop.body1:
br i1 undef, label %loop.body3, label %loop.body2
loop.body2:
%ptr = load i32** undef, align 4
br label %loop.body3
loop.body3:
%myptr = phi i32* [ %ptr2, %loop.body5 ], [ %ptr, %loop.body2 ], [ undef, %loop.body1 ]
%bcmyptr = bitcast i32* %myptr to i32*
%val = load i32* %bcmyptr, align 4
%comp = icmp eq i32 %val, 48
br i1 %comp, label %loop.body4, label %loop.body5
loop.body4:
br i1 undef, label %loop.header, label %loop.body5
loop.body5:
%ptr2 = load i32** undef, align 4
br label %loop.body3
}
define void @unnatural_cfg2() {
; Test that we can handle a loop with a nested natural loop *and* an unnatural
; loop. This was reduced from a crash on block placement when run over
; single-source GCC.
; CHECK: unnatural_cfg2
; CHECK: %entry
; CHECK: %loop.body1
; CHECK: %loop.body2
; CHECK: %loop.body3
; CHECK: %loop.inner1.begin
; The end block is folded with %loop.body3...
; CHECK-NOT: %loop.inner1.end
; CHECK: %loop.body4
; CHECK: %loop.inner2.begin
; The loop.inner2.end block is folded
Rewrite how machine block placement handles loop rotation. This is a complex change that resulted from a great deal of experimentation with several different benchmarks. The one which proved the most useful is included as a test case, but I don't know that it captures all of the relevant changes, as I didn't have specific regression tests for each, they were more the result of reasoning about what the old algorithm would possibly do wrong. I'm also failing at the moment to craft more targeted regression tests for these changes, if anyone has ideas, it would be welcome. The first big thing broken with the old algorithm is the idea that we can take a basic block which has a loop-exiting successor and a looping successor and use the looping successor as the layout top in order to get that particular block to be the bottom of the loop after layout. This happens to work in many cases, but not in all. The second big thing broken was that we didn't try to select the exit which fell into the nearest enclosing loop (to which we exit at all). As a consequence, even if the rotation worked perfectly, it would result in one of two bad layouts. Either the bottom of the loop would get fallthrough, skipping across a nearer enclosing loop and thereby making it discontiguous, or it would be forced to take an explicit jump over the nearest enclosing loop to earch its successor. The point of the rotation is to get fallthrough, so we need it to fallthrough to the nearest loop it can. The fix to the first issue is to actually layout the loop from the loop header, and then rotate the loop such that the correct exiting edge can be a fallthrough edge. This is actually much easier than I anticipated because we can handle all the hard parts of finding a viable rotation before we do the layout. We just store that, and then rotate after layout is finished. No inner loops get split across the post-rotation backedge because we check for them when selecting the rotation. That fix exposed a latent problem with our exitting block selection -- we should allow the backedge to point into the middle of some inner-loop chain as there is no real penalty to it, the whole point is that it *won't* be a fallthrough edge. This may have blocked the rotation at all in some cases, I have no idea and no test case as I've never seen it in practice, it was just noticed by inspection. Finally, all of these fixes, and studying the loops they produce, highlighted another problem: in rotating loops like this, we sometimes fail to align the destination of these backwards jumping edges. Fix this by actually walking the backwards edges rather than relying on loopinfo. This fixes regressions on heapsort if block placement is enabled as well as lots of other cases where the previous logic would introduce an abundance of unnecessary branches into the execution. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154783 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-16 01:12:56 +00:00
; CHECK: %loop.header
; CHECK: %bail
entry:
br label %loop.header
loop.header:
%comp0 = icmp eq i32* undef, null
br i1 %comp0, label %bail, label %loop.body1
loop.body1:
%val0 = load i32** undef, align 4
br i1 undef, label %loop.body2, label %loop.inner1.begin
loop.body2:
br i1 undef, label %loop.body4, label %loop.body3
loop.body3:
%ptr1 = getelementptr inbounds i32* %val0, i32 0
%castptr1 = bitcast i32* %ptr1 to i32**
%val1 = load i32** %castptr1, align 4
br label %loop.inner1.begin
loop.inner1.begin:
%valphi = phi i32* [ %val2, %loop.inner1.end ], [ %val1, %loop.body3 ], [ %val0, %loop.body1 ]
%castval = bitcast i32* %valphi to i32*
%comp1 = icmp eq i32 undef, 48
br i1 %comp1, label %loop.inner1.end, label %loop.body4
loop.inner1.end:
%ptr2 = getelementptr inbounds i32* %valphi, i32 0
%castptr2 = bitcast i32* %ptr2 to i32**
%val2 = load i32** %castptr2, align 4
br label %loop.inner1.begin
loop.body4.dead:
br label %loop.body4
loop.body4:
%comp2 = icmp ult i32 undef, 3
br i1 %comp2, label %loop.inner2.begin, label %loop.end
loop.inner2.begin:
br i1 false, label %loop.end, label %loop.inner2.end
loop.inner2.end:
%comp3 = icmp eq i32 undef, 1769472
br i1 %comp3, label %loop.end, label %loop.inner2.begin
loop.end:
br label %loop.header
bail:
unreachable
}
define i32 @problematic_switch() {
; This function's CFG caused overlow in the machine branch probability
; calculation, triggering asserts. Make sure we don't crash on it.
; CHECK: problematic_switch
entry:
switch i32 undef, label %exit [
i32 879, label %bogus
i32 877, label %step
i32 876, label %step
i32 875, label %step
i32 874, label %step
i32 873, label %step
i32 872, label %step
i32 868, label %step
i32 867, label %step
i32 866, label %step
i32 861, label %step
i32 860, label %step
i32 856, label %step
i32 855, label %step
i32 854, label %step
i32 831, label %step
i32 830, label %step
i32 829, label %step
i32 828, label %step
i32 815, label %step
i32 814, label %step
i32 811, label %step
i32 806, label %step
i32 805, label %step
i32 804, label %step
i32 803, label %step
i32 802, label %step
i32 801, label %step
i32 800, label %step
i32 799, label %step
i32 798, label %step
i32 797, label %step
i32 796, label %step
i32 795, label %step
]
bogus:
unreachable
step:
br label %exit
exit:
%merge = phi i32 [ 3, %step ], [ 6, %entry ]
ret i32 %merge
}
define void @fpcmp_unanalyzable_branch(i1 %cond) {
; This function's CFG contains an unanalyzable branch that is likely to be
; split due to having a different high-probability predecessor.
; CHECK: fpcmp_unanalyzable_branch
; CHECK: %entry
; CHECK: %exit
; CHECK-NOT: %if.then
; CHECK-NOT: %if.end
; CHECK-NOT: jne
; CHECK-NOT: jnp
; CHECK: jne
; CHECK-NEXT: jnp
; CHECK-NEXT: %if.then
entry:
; Note that this branch must be strongly biased toward
; 'entry.if.then_crit_edge' to ensure that we would try to form a chain for
; 'entry' -> 'entry.if.then_crit_edge' -> 'if.then'. It is the last edge in that
; chain which would violate the unanalyzable branch in 'exit', but we won't even
; try this trick unless 'if.then' is believed to almost always be reached from
; 'entry.if.then_crit_edge'.
br i1 %cond, label %entry.if.then_crit_edge, label %lor.lhs.false, !prof !1
entry.if.then_crit_edge:
%.pre14 = load i8* undef, align 1, !tbaa !0
br label %if.then
lor.lhs.false:
br i1 undef, label %if.end, label %exit
exit:
%cmp.i = fcmp une double 0.000000e+00, undef
br i1 %cmp.i, label %if.then, label %if.end
if.then:
%0 = phi i8 [ %.pre14, %entry.if.then_crit_edge ], [ undef, %exit ]
%1 = and i8 %0, 1
store i8 %1, i8* undef, align 4, !tbaa !0
br label %if.end
if.end:
ret void
}
!1 = metadata !{metadata !"branch_weights", i32 1000, i32 1}
declare i32 @f()
declare i32 @g()
declare i32 @h(i32 %x)
define i32 @test_global_cfg_break_profitability() {
; Check that our metrics for the profitability of a CFG break are global rather
; than local. A successor may be very hot, but if the current block isn't, it
; doesn't matter. Within this test the 'then' block is slightly warmer than the
; 'else' block, but not nearly enough to merit merging it with the exit block
; even though the probability of 'then' branching to the 'exit' block is very
; high.
; CHECK: test_global_cfg_break_profitability
; CHECK: calll {{_?}}f
; CHECK: calll {{_?}}g
; CHECK: calll {{_?}}h
; CHECK: ret
entry:
br i1 undef, label %then, label %else, !prof !2
then:
%then.result = call i32 @f()
br label %exit
else:
%else.result = call i32 @g()
br label %exit
exit:
%result = phi i32 [ %then.result, %then ], [ %else.result, %else ]
%result2 = call i32 @h(i32 %result)
ret i32 %result
}
!2 = metadata !{metadata !"branch_weights", i32 3, i32 1}
declare i32 @__gxx_personality_v0(...)
define void @test_eh_lpad_successor() {
; Some times the landing pad ends up as the first successor of an invoke block.
; When this happens, a strange result used to fall out of updateTerminators: we
; didn't correctly locate the fallthrough successor, assuming blindly that the
; first one was the fallthrough successor. As a result, we would add an
; erroneous jump to the landing pad thinking *that* was the default successor.
; CHECK: test_eh_lpad_successor
; CHECK: %entry
; CHECK-NOT: jmp
; CHECK: %loop
entry:
invoke i32 @f() to label %preheader unwind label %lpad
preheader:
br label %loop
lpad:
%lpad.val = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
cleanup
resume { i8*, i32 } %lpad.val
loop:
br label %loop
}
declare void @fake_throw() noreturn
define void @test_eh_throw() {
; For blocks containing a 'throw' (or similar functionality), we have
; a no-return invoke. In this case, only EH successors will exist, and
; fallthrough simply won't occur. Make sure we don't crash trying to update
; terminators for such constructs.
;
; CHECK: test_eh_throw
; CHECK: %entry
; CHECK: %cleanup
entry:
invoke void @fake_throw() to label %continue unwind label %cleanup
continue:
unreachable
cleanup:
%0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
cleanup
unreachable
}
define void @test_unnatural_cfg_backwards_inner_loop() {
; Test that when we encounter an unnatural CFG structure after having formed
; a chain for an inner loop which happened to be laid out backwards we don't
; attempt to merge onto the wrong end of the inner loop just because we find it
; first. This was reduced from a crasher in GCC's single source.
;
; CHECK: test_unnatural_cfg_backwards_inner_loop
; CHECK: %entry
; CHECK: %body
; CHECK: %loop2b
; CHECK: %loop1
; CHECK: %loop2a
entry:
br i1 undef, label %loop2a, label %body
body:
br label %loop2a
loop1:
%next.load = load i32** undef
br i1 %comp.a, label %loop2a, label %loop2b
loop2a:
%var = phi i32* [ null, %entry ], [ null, %body ], [ %next.phi, %loop1 ]
%next.var = phi i32* [ null, %entry ], [ undef, %body ], [ %next.load, %loop1 ]
%comp.a = icmp eq i32* %var, null
br label %loop3
loop2b:
%gep = getelementptr inbounds i32* %var.phi, i32 0
%next.ptr = bitcast i32* %gep to i32**
store i32* %next.phi, i32** %next.ptr
br label %loop3
loop3:
%var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ]
%next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ]
br label %loop1
}
define void @unanalyzable_branch_to_loop_header() {
; Ensure that we can handle unanalyzable branches into loop headers. We
; pre-form chains for unanalyzable branches, and will find the tail end of that
; at the start of the loop. This function uses floating point comparison
; fallthrough because that happens to always produce unanalyzable branches on
; x86.
;
; CHECK: unanalyzable_branch_to_loop_header
; CHECK: %entry
; CHECK: %loop
; CHECK: %exit
entry:
%cmp = fcmp une double 0.000000e+00, undef
br i1 %cmp, label %loop, label %exit
loop:
%cond = icmp eq i8 undef, 42
br i1 %cond, label %exit, label %loop
exit:
ret void
}
define void @unanalyzable_branch_to_best_succ(i1 %cond) {
; Ensure that we can handle unanalyzable branches where the destination block
; gets selected as the optimal sucessor to merge.
;
; CHECK: unanalyzable_branch_to_best_succ
; CHECK: %entry
; CHECK: %foo
; CHECK: %bar
; CHECK: %exit
entry:
; Bias this branch toward bar to ensure we form that chain.
br i1 %cond, label %bar, label %foo, !prof !1
foo:
%cmp = fcmp une double 0.000000e+00, undef
br i1 %cmp, label %bar, label %exit
bar:
call i32 @f()
br label %exit
exit:
ret void
}
define void @unanalyzable_branch_to_free_block(float %x) {
; Ensure that we can handle unanalyzable branches where the destination block
; gets selected as the best free block in the CFG.
;
; CHECK: unanalyzable_branch_to_free_block
; CHECK: %entry
; CHECK: %a
; CHECK: %b
; CHECK: %c
; CHECK: %exit
entry:
br i1 undef, label %a, label %b
a:
call i32 @f()
br label %c
b:
%cmp = fcmp une float %x, undef
br i1 %cmp, label %c, label %exit
c:
call i32 @g()
br label %exit
exit:
ret void
}
define void @many_unanalyzable_branches() {
; Ensure that we don't crash as we're building up many unanalyzable branches,
; blocks, and loops.
;
; CHECK: many_unanalyzable_branches
; CHECK: %entry
; CHECK: %exit
entry:
br label %0
%val0 = load volatile float* undef
%cmp0 = fcmp une float %val0, undef
br i1 %cmp0, label %1, label %0
%val1 = load volatile float* undef
%cmp1 = fcmp une float %val1, undef
br i1 %cmp1, label %2, label %1
%val2 = load volatile float* undef
%cmp2 = fcmp une float %val2, undef
br i1 %cmp2, label %3, label %2
%val3 = load volatile float* undef
%cmp3 = fcmp une float %val3, undef
br i1 %cmp3, label %4, label %3
%val4 = load volatile float* undef
%cmp4 = fcmp une float %val4, undef
br i1 %cmp4, label %5, label %4
%val5 = load volatile float* undef
%cmp5 = fcmp une float %val5, undef
br i1 %cmp5, label %6, label %5
%val6 = load volatile float* undef
%cmp6 = fcmp une float %val6, undef
br i1 %cmp6, label %7, label %6
%val7 = load volatile float* undef
%cmp7 = fcmp une float %val7, undef
br i1 %cmp7, label %8, label %7
%val8 = load volatile float* undef
%cmp8 = fcmp une float %val8, undef
br i1 %cmp8, label %9, label %8
%val9 = load volatile float* undef
%cmp9 = fcmp une float %val9, undef
br i1 %cmp9, label %10, label %9
%val10 = load volatile float* undef
%cmp10 = fcmp une float %val10, undef
br i1 %cmp10, label %11, label %10
%val11 = load volatile float* undef
%cmp11 = fcmp une float %val11, undef
br i1 %cmp11, label %12, label %11
%val12 = load volatile float* undef
%cmp12 = fcmp une float %val12, undef
br i1 %cmp12, label %13, label %12
%val13 = load volatile float* undef
%cmp13 = fcmp une float %val13, undef
br i1 %cmp13, label %14, label %13
%val14 = load volatile float* undef
%cmp14 = fcmp une float %val14, undef
br i1 %cmp14, label %15, label %14
%val15 = load volatile float* undef
%cmp15 = fcmp une float %val15, undef
br i1 %cmp15, label %16, label %15
%val16 = load volatile float* undef
%cmp16 = fcmp une float %val16, undef
br i1 %cmp16, label %17, label %16
%val17 = load volatile float* undef
%cmp17 = fcmp une float %val17, undef
br i1 %cmp17, label %18, label %17
%val18 = load volatile float* undef
%cmp18 = fcmp une float %val18, undef
br i1 %cmp18, label %19, label %18
%val19 = load volatile float* undef
%cmp19 = fcmp une float %val19, undef
br i1 %cmp19, label %20, label %19
%val20 = load volatile float* undef
%cmp20 = fcmp une float %val20, undef
br i1 %cmp20, label %21, label %20
%val21 = load volatile float* undef
%cmp21 = fcmp une float %val21, undef
br i1 %cmp21, label %22, label %21
%val22 = load volatile float* undef
%cmp22 = fcmp une float %val22, undef
br i1 %cmp22, label %23, label %22
%val23 = load volatile float* undef
%cmp23 = fcmp une float %val23, undef
br i1 %cmp23, label %24, label %23
%val24 = load volatile float* undef
%cmp24 = fcmp une float %val24, undef
br i1 %cmp24, label %25, label %24
%val25 = load volatile float* undef
%cmp25 = fcmp une float %val25, undef
br i1 %cmp25, label %26, label %25
%val26 = load volatile float* undef
%cmp26 = fcmp une float %val26, undef
br i1 %cmp26, label %27, label %26
%val27 = load volatile float* undef
%cmp27 = fcmp une float %val27, undef
br i1 %cmp27, label %28, label %27
%val28 = load volatile float* undef
%cmp28 = fcmp une float %val28, undef
br i1 %cmp28, label %29, label %28
%val29 = load volatile float* undef
%cmp29 = fcmp une float %val29, undef
br i1 %cmp29, label %30, label %29
%val30 = load volatile float* undef
%cmp30 = fcmp une float %val30, undef
br i1 %cmp30, label %31, label %30
%val31 = load volatile float* undef
%cmp31 = fcmp une float %val31, undef
br i1 %cmp31, label %32, label %31
%val32 = load volatile float* undef
%cmp32 = fcmp une float %val32, undef
br i1 %cmp32, label %33, label %32
%val33 = load volatile float* undef
%cmp33 = fcmp une float %val33, undef
br i1 %cmp33, label %34, label %33
%val34 = load volatile float* undef
%cmp34 = fcmp une float %val34, undef
br i1 %cmp34, label %35, label %34
%val35 = load volatile float* undef
%cmp35 = fcmp une float %val35, undef
br i1 %cmp35, label %36, label %35
%val36 = load volatile float* undef
%cmp36 = fcmp une float %val36, undef
br i1 %cmp36, label %37, label %36
%val37 = load volatile float* undef
%cmp37 = fcmp une float %val37, undef
br i1 %cmp37, label %38, label %37
%val38 = load volatile float* undef
%cmp38 = fcmp une float %val38, undef
br i1 %cmp38, label %39, label %38
%val39 = load volatile float* undef
%cmp39 = fcmp une float %val39, undef
br i1 %cmp39, label %40, label %39
%val40 = load volatile float* undef
%cmp40 = fcmp une float %val40, undef
br i1 %cmp40, label %41, label %40
%val41 = load volatile float* undef
%cmp41 = fcmp une float %val41, undef
br i1 %cmp41, label %42, label %41
%val42 = load volatile float* undef
%cmp42 = fcmp une float %val42, undef
br i1 %cmp42, label %43, label %42
%val43 = load volatile float* undef
%cmp43 = fcmp une float %val43, undef
br i1 %cmp43, label %44, label %43
%val44 = load volatile float* undef
%cmp44 = fcmp une float %val44, undef
br i1 %cmp44, label %45, label %44
%val45 = load volatile float* undef
%cmp45 = fcmp une float %val45, undef
br i1 %cmp45, label %46, label %45
%val46 = load volatile float* undef
%cmp46 = fcmp une float %val46, undef
br i1 %cmp46, label %47, label %46
%val47 = load volatile float* undef
%cmp47 = fcmp une float %val47, undef
br i1 %cmp47, label %48, label %47
%val48 = load volatile float* undef
%cmp48 = fcmp une float %val48, undef
br i1 %cmp48, label %49, label %48
%val49 = load volatile float* undef
%cmp49 = fcmp une float %val49, undef
br i1 %cmp49, label %50, label %49
%val50 = load volatile float* undef
%cmp50 = fcmp une float %val50, undef
br i1 %cmp50, label %51, label %50
%val51 = load volatile float* undef
%cmp51 = fcmp une float %val51, undef
br i1 %cmp51, label %52, label %51
%val52 = load volatile float* undef
%cmp52 = fcmp une float %val52, undef
br i1 %cmp52, label %53, label %52
%val53 = load volatile float* undef
%cmp53 = fcmp une float %val53, undef
br i1 %cmp53, label %54, label %53
%val54 = load volatile float* undef
%cmp54 = fcmp une float %val54, undef
br i1 %cmp54, label %55, label %54
%val55 = load volatile float* undef
%cmp55 = fcmp une float %val55, undef
br i1 %cmp55, label %56, label %55
%val56 = load volatile float* undef
%cmp56 = fcmp une float %val56, undef
br i1 %cmp56, label %57, label %56
%val57 = load volatile float* undef
%cmp57 = fcmp une float %val57, undef
br i1 %cmp57, label %58, label %57
%val58 = load volatile float* undef
%cmp58 = fcmp une float %val58, undef
br i1 %cmp58, label %59, label %58
%val59 = load volatile float* undef
%cmp59 = fcmp une float %val59, undef
br i1 %cmp59, label %60, label %59
%val60 = load volatile float* undef
%cmp60 = fcmp une float %val60, undef
br i1 %cmp60, label %61, label %60
%val61 = load volatile float* undef
%cmp61 = fcmp une float %val61, undef
br i1 %cmp61, label %62, label %61
%val62 = load volatile float* undef
%cmp62 = fcmp une float %val62, undef
br i1 %cmp62, label %63, label %62
%val63 = load volatile float* undef
%cmp63 = fcmp une float %val63, undef
br i1 %cmp63, label %64, label %63
%val64 = load volatile float* undef
%cmp64 = fcmp une float %val64, undef
br i1 %cmp64, label %65, label %64
br label %exit
exit:
ret void
}
Rewrite how machine block placement handles loop rotation. This is a complex change that resulted from a great deal of experimentation with several different benchmarks. The one which proved the most useful is included as a test case, but I don't know that it captures all of the relevant changes, as I didn't have specific regression tests for each, they were more the result of reasoning about what the old algorithm would possibly do wrong. I'm also failing at the moment to craft more targeted regression tests for these changes, if anyone has ideas, it would be welcome. The first big thing broken with the old algorithm is the idea that we can take a basic block which has a loop-exiting successor and a looping successor and use the looping successor as the layout top in order to get that particular block to be the bottom of the loop after layout. This happens to work in many cases, but not in all. The second big thing broken was that we didn't try to select the exit which fell into the nearest enclosing loop (to which we exit at all). As a consequence, even if the rotation worked perfectly, it would result in one of two bad layouts. Either the bottom of the loop would get fallthrough, skipping across a nearer enclosing loop and thereby making it discontiguous, or it would be forced to take an explicit jump over the nearest enclosing loop to earch its successor. The point of the rotation is to get fallthrough, so we need it to fallthrough to the nearest loop it can. The fix to the first issue is to actually layout the loop from the loop header, and then rotate the loop such that the correct exiting edge can be a fallthrough edge. This is actually much easier than I anticipated because we can handle all the hard parts of finding a viable rotation before we do the layout. We just store that, and then rotate after layout is finished. No inner loops get split across the post-rotation backedge because we check for them when selecting the rotation. That fix exposed a latent problem with our exitting block selection -- we should allow the backedge to point into the middle of some inner-loop chain as there is no real penalty to it, the whole point is that it *won't* be a fallthrough edge. This may have blocked the rotation at all in some cases, I have no idea and no test case as I've never seen it in practice, it was just noticed by inspection. Finally, all of these fixes, and studying the loops they produce, highlighted another problem: in rotating loops like this, we sometimes fail to align the destination of these backwards jumping edges. Fix this by actually walking the backwards edges rather than relying on loopinfo. This fixes regressions on heapsort if block placement is enabled as well as lots of other cases where the previous logic would introduce an abundance of unnecessary branches into the execution. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154783 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-16 01:12:56 +00:00
define void @benchmark_heapsort(i32 %n, double* nocapture %ra) {
; This test case comes from the heapsort benchmark, and exemplifies several
; important aspects to block placement in the presence of loops:
; 1) Loop rotation needs to *ensure* that the desired exiting edge can be
; a fallthrough.
; 2) The exiting edge from the loop which is rotated to be laid out at the
; bottom of the loop needs to be exiting into the nearest enclosing loop (to
; which there is an exit). Otherwise, we force that enclosing loop into
; strange layouts that are siginificantly less efficient, often times maing
; it discontiguous.
;
; CHECK: @benchmark_heapsort
; CHECK: %entry
; First rotated loop top.
; CHECK: .align
; CHECK: %while.end
; CHECK: %for.cond
; CHECK: %if.then
; CHECK: %if.else
Rewrite how machine block placement handles loop rotation. This is a complex change that resulted from a great deal of experimentation with several different benchmarks. The one which proved the most useful is included as a test case, but I don't know that it captures all of the relevant changes, as I didn't have specific regression tests for each, they were more the result of reasoning about what the old algorithm would possibly do wrong. I'm also failing at the moment to craft more targeted regression tests for these changes, if anyone has ideas, it would be welcome. The first big thing broken with the old algorithm is the idea that we can take a basic block which has a loop-exiting successor and a looping successor and use the looping successor as the layout top in order to get that particular block to be the bottom of the loop after layout. This happens to work in many cases, but not in all. The second big thing broken was that we didn't try to select the exit which fell into the nearest enclosing loop (to which we exit at all). As a consequence, even if the rotation worked perfectly, it would result in one of two bad layouts. Either the bottom of the loop would get fallthrough, skipping across a nearer enclosing loop and thereby making it discontiguous, or it would be forced to take an explicit jump over the nearest enclosing loop to earch its successor. The point of the rotation is to get fallthrough, so we need it to fallthrough to the nearest loop it can. The fix to the first issue is to actually layout the loop from the loop header, and then rotate the loop such that the correct exiting edge can be a fallthrough edge. This is actually much easier than I anticipated because we can handle all the hard parts of finding a viable rotation before we do the layout. We just store that, and then rotate after layout is finished. No inner loops get split across the post-rotation backedge because we check for them when selecting the rotation. That fix exposed a latent problem with our exitting block selection -- we should allow the backedge to point into the middle of some inner-loop chain as there is no real penalty to it, the whole point is that it *won't* be a fallthrough edge. This may have blocked the rotation at all in some cases, I have no idea and no test case as I've never seen it in practice, it was just noticed by inspection. Finally, all of these fixes, and studying the loops they produce, highlighted another problem: in rotating loops like this, we sometimes fail to align the destination of these backwards jumping edges. Fix this by actually walking the backwards edges rather than relying on loopinfo. This fixes regressions on heapsort if block placement is enabled as well as lots of other cases where the previous logic would introduce an abundance of unnecessary branches into the execution. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154783 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-16 01:12:56 +00:00
; CHECK: %if.end10
; Second rotated loop top
; CHECK: .align
; CHECK: %if.then24
Rewrite how machine block placement handles loop rotation. This is a complex change that resulted from a great deal of experimentation with several different benchmarks. The one which proved the most useful is included as a test case, but I don't know that it captures all of the relevant changes, as I didn't have specific regression tests for each, they were more the result of reasoning about what the old algorithm would possibly do wrong. I'm also failing at the moment to craft more targeted regression tests for these changes, if anyone has ideas, it would be welcome. The first big thing broken with the old algorithm is the idea that we can take a basic block which has a loop-exiting successor and a looping successor and use the looping successor as the layout top in order to get that particular block to be the bottom of the loop after layout. This happens to work in many cases, but not in all. The second big thing broken was that we didn't try to select the exit which fell into the nearest enclosing loop (to which we exit at all). As a consequence, even if the rotation worked perfectly, it would result in one of two bad layouts. Either the bottom of the loop would get fallthrough, skipping across a nearer enclosing loop and thereby making it discontiguous, or it would be forced to take an explicit jump over the nearest enclosing loop to earch its successor. The point of the rotation is to get fallthrough, so we need it to fallthrough to the nearest loop it can. The fix to the first issue is to actually layout the loop from the loop header, and then rotate the loop such that the correct exiting edge can be a fallthrough edge. This is actually much easier than I anticipated because we can handle all the hard parts of finding a viable rotation before we do the layout. We just store that, and then rotate after layout is finished. No inner loops get split across the post-rotation backedge because we check for them when selecting the rotation. That fix exposed a latent problem with our exitting block selection -- we should allow the backedge to point into the middle of some inner-loop chain as there is no real penalty to it, the whole point is that it *won't* be a fallthrough edge. This may have blocked the rotation at all in some cases, I have no idea and no test case as I've never seen it in practice, it was just noticed by inspection. Finally, all of these fixes, and studying the loops they produce, highlighted another problem: in rotating loops like this, we sometimes fail to align the destination of these backwards jumping edges. Fix this by actually walking the backwards edges rather than relying on loopinfo. This fixes regressions on heapsort if block placement is enabled as well as lots of other cases where the previous logic would introduce an abundance of unnecessary branches into the execution. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154783 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-16 01:12:56 +00:00
; CHECK: %while.cond.outer
; Third rotated loop top
; CHECK: .align
; CHECK: %while.cond
; CHECK: %while.body
; CHECK: %land.lhs.true
; CHECK: %if.then19
; CHECK: %if.then19
; CHECK: %if.then8
; CHECK: ret
entry:
%shr = ashr i32 %n, 1
%add = add nsw i32 %shr, 1
%arrayidx3 = getelementptr inbounds double* %ra, i64 1
br label %for.cond
for.cond:
%ir.0 = phi i32 [ %n, %entry ], [ %ir.1, %while.end ]
%l.0 = phi i32 [ %add, %entry ], [ %l.1, %while.end ]
%cmp = icmp sgt i32 %l.0, 1
br i1 %cmp, label %if.then, label %if.else
if.then:
%dec = add nsw i32 %l.0, -1
%idxprom = sext i32 %dec to i64
%arrayidx = getelementptr inbounds double* %ra, i64 %idxprom
%0 = load double* %arrayidx, align 8
br label %if.end10
if.else:
%idxprom1 = sext i32 %ir.0 to i64
%arrayidx2 = getelementptr inbounds double* %ra, i64 %idxprom1
%1 = load double* %arrayidx2, align 8
%2 = load double* %arrayidx3, align 8
store double %2, double* %arrayidx2, align 8
%dec6 = add nsw i32 %ir.0, -1
%cmp7 = icmp eq i32 %dec6, 1
br i1 %cmp7, label %if.then8, label %if.end10
if.then8:
store double %1, double* %arrayidx3, align 8
ret void
if.end10:
%ir.1 = phi i32 [ %ir.0, %if.then ], [ %dec6, %if.else ]
%l.1 = phi i32 [ %dec, %if.then ], [ %l.0, %if.else ]
%rra.0 = phi double [ %0, %if.then ], [ %1, %if.else ]
%add31 = add nsw i32 %ir.1, 1
br label %while.cond.outer
while.cond.outer:
%j.0.ph.in = phi i32 [ %l.1, %if.end10 ], [ %j.1, %if.then24 ]
%j.0.ph = shl i32 %j.0.ph.in, 1
br label %while.cond
while.cond:
%j.0 = phi i32 [ %add31, %if.end20 ], [ %j.0.ph, %while.cond.outer ]
%cmp11 = icmp sgt i32 %j.0, %ir.1
br i1 %cmp11, label %while.end, label %while.body
while.body:
%cmp12 = icmp slt i32 %j.0, %ir.1
br i1 %cmp12, label %land.lhs.true, label %if.end20
land.lhs.true:
%idxprom13 = sext i32 %j.0 to i64
%arrayidx14 = getelementptr inbounds double* %ra, i64 %idxprom13
%3 = load double* %arrayidx14, align 8
%add15 = add nsw i32 %j.0, 1
%idxprom16 = sext i32 %add15 to i64
%arrayidx17 = getelementptr inbounds double* %ra, i64 %idxprom16
%4 = load double* %arrayidx17, align 8
%cmp18 = fcmp olt double %3, %4
br i1 %cmp18, label %if.then19, label %if.end20
if.then19:
br label %if.end20
if.end20:
%j.1 = phi i32 [ %add15, %if.then19 ], [ %j.0, %land.lhs.true ], [ %j.0, %while.body ]
%idxprom21 = sext i32 %j.1 to i64
%arrayidx22 = getelementptr inbounds double* %ra, i64 %idxprom21
%5 = load double* %arrayidx22, align 8
%cmp23 = fcmp olt double %rra.0, %5
br i1 %cmp23, label %if.then24, label %while.cond
if.then24:
%idxprom27 = sext i32 %j.0.ph.in to i64
%arrayidx28 = getelementptr inbounds double* %ra, i64 %idxprom27
store double %5, double* %arrayidx28, align 8
br label %while.cond.outer
while.end:
%idxprom33 = sext i32 %j.0.ph.in to i64
%arrayidx34 = getelementptr inbounds double* %ra, i64 %idxprom33
store double %rra.0, double* %arrayidx34, align 8
br label %for.cond
}