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https://github.com/c64scene-ar/llvm-6502.git
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Revert "blockfreq: Approximate irreducible control flow"
This reverts commit r207286. It causes an ICE on the
cmake-llvm-x86_64-linux buildbot [1]:
llvm/lib/Analysis/BlockFrequencyInfo.cpp: In lambda function:
llvm/lib/Analysis/BlockFrequencyInfo.cpp:182:1: internal compiler error: in get_expr_operands, at tree-ssa-operands.c:1035
[1]: http://bb.pgr.jp/builders/cmake-llvm-x86_64-linux/builds/12093/steps/build_llvm/logs/stdio
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207287 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith
@@ -34,28 +34,16 @@ return:
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!0 = metadata !{metadata !"branch_weights", i32 1, i32 7}
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!1 = metadata !{metadata !"branch_weights", i32 3, i32 4}
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; Irreducible control flow
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; ========================
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; The current BlockFrequencyInfo algorithm doesn't handle multiple entrances
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; into a loop very well. The frequencies assigned to blocks in the loop are
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; predictable (and not absurd), but also not correct and therefore not worth
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; testing.
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;
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; LoopInfo defines a loop as a non-trivial SCC dominated by a single block,
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; called the header. A given loop, L, can have sub-loops, which are loops
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; within the subgraph of L that excludes the header.
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; There are two testcases below.
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;
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; In addition to loops, -block-freq has limited support for irreducible SCCs,
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; which are SCCs with multiple entry blocks. Irreducible SCCs are discovered
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; on they fly, and modelled as loops with multiple headers.
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;
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; The headers of irreducible sub-SCCs consist of its entry blocks and all nodes
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; that are targets of a backedge within it (excluding backedges within true
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; sub-loops).
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;
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; -block-freq is currently designed to act like a block is inserted that
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; intercepts all the edges to the headers. All backedges and entries point to
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; this block. Its successors are the headers, which split the frequency
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; evenly.
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;
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; There are a number of testcases below. Only the first two have detailed
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; explanations.
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; For each testcase, I use a CHECK-NEXT/NOT combo like an XFAIL with the
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; granularity of a single check. If/when this behaviour is fixed, we'll know
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; about it, and the test should be updated.
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;
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; Testcase #1
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; ===========
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@@ -89,31 +77,36 @@ return:
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; loop as a whole is 1/4, so the loop scale should be 4. Summing c1 and c2
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; gives 28/7, or 4.0, which is nice confirmation of the math above.
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;
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; -block-freq currently treats the two nodes as equals.
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define void @multientry(i1 %x) {
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; However, assuming c1 precedes c2 in reverse post-order, the current algorithm
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; returns 3/4 and 13/16, respectively. LoopInfo ignores edges between loops
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; (and doesn't see any loops here at all), and -block-freq ignores the
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; irreducible edge from c2 to c1.
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;
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; CHECK-LABEL: Printing analysis {{.*}} for function 'multientry':
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; CHECK-NEXT: block-frequency-info: multientry
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entry:
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define void @multientry(i1 %x) {
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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entry:
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br i1 %x, label %c1, label %c2, !prof !2
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; This is like a single-line XFAIL (see above).
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; CHECK-NEXT: c1:
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; CHECK-NOT: float = 2.142857{{[0-9]*}},
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c1:
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; CHECK-NEXT: c1: float = 2.0,
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; The "correct" answer is: float = 2.142857{{[0-9]*}},
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br i1 %x, label %c2, label %exit, !prof !2
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; This is like a single-line XFAIL (see above).
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; CHECK-NEXT: c2:
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; CHECK-NOT: float = 1.857142{{[0-9]*}},
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c2:
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; CHECK-NEXT: c2: float = 2.0,
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; The "correct" answer is: float = 1.857142{{[0-9]*}},
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br i1 %x, label %c1, label %exit, !prof !2
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exit:
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; We still shouldn't lose any frequency.
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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exit:
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ret void
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}
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!2 = metadata !{metadata !"branch_weights", i32 3, i32 1}
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; Testcase #2
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; ===========
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;
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@@ -131,291 +124,73 @@ exit:
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; step, c1 and c2 each get 1/3 of what's left in c1 and c2 combined. This
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; infinite series sums to 1.
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;
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; Since the currently algorithm *always* assumes entry blocks are equal,
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; -block-freq gets the right answers here.
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define void @crossloops(i2 %x) {
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; However, assuming c1 precedes c2 in reverse post-order, the current algorithm
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; returns 1/2 and 3/4, respectively. LoopInfo ignores edges between loops (and
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; treats c1 and c2 as self-loops only), and -block-freq ignores the irreducible
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; edge from c2 to c1.
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;
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; Below I use a CHECK-NEXT/NOT combo like an XFAIL with the granularity of a
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; single check. If/when this behaviour is fixed, we'll know about it, and the
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; test should be updated.
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;
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; CHECK-LABEL: Printing analysis {{.*}} for function 'crossloops':
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; CHECK-NEXT: block-frequency-info: crossloops
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entry:
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define void @crossloops(i2 %x) {
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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entry:
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switch i2 %x, label %exit [ i2 1, label %c1
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i2 2, label %c2 ], !prof !3
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; This is like a single-line XFAIL (see above).
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; CHECK-NEXT: c1:
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; CHECK-NOT: float = 1.0,
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c1:
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; CHECK-NEXT: c1: float = 1.0,
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switch i2 %x, label %exit [ i2 1, label %c1
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i2 2, label %c2 ], !prof !3
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; This is like a single-line XFAIL (see above).
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; CHECK-NEXT: c2:
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; CHECK-NOT: float = 1.0,
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c2:
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; CHECK-NEXT: c2: float = 1.0,
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switch i2 %x, label %exit [ i2 1, label %c1
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i2 2, label %c2 ], !prof !3
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exit:
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; We still shouldn't lose any frequency.
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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exit:
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ret void
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}
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!2 = metadata !{metadata !"branch_weights", i32 3, i32 1}
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!3 = metadata !{metadata !"branch_weights", i32 2, i32 2, i32 2}
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; A true loop with irreducible control flow inside.
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define void @loop_around_irreducible(i1 %x) {
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; A reducible loop with irreducible control flow inside should still have
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; correct exit frequency.
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;
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; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_irreducible':
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; CHECK-NEXT: block-frequency-info: loop_around_irreducible
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entry:
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define void @loop_around_irreducible(i1 %x) {
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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entry:
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br label %loop
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; CHECK-NEXT: loop: float = [[HEAD:[0-9.]+]], int = [[HEADINT:[0-9]+]]
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loop:
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; CHECK-NEXT: loop: float = 4.0, int = [[HEAD:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !4
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br i1 %x, label %left, label %right
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; CHECK-NEXT: left:
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left:
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; CHECK-NEXT: left: float = 8.0,
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br i1 %x, label %right, label %loop.end, !prof !5
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br i1 %x, label %right, label %loop.end
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; CHECK-NEXT: right:
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right:
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; CHECK-NEXT: right: float = 8.0,
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br i1 %x, label %left, label %loop.end, !prof !5
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br i1 %x, label %left, label %loop.end
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; CHECK-NEXT: loop.end: float = [[HEAD]], int = [[HEADINT]]
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loop.end:
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; CHECK-NEXT: loop.end: float = 4.0, int = [[HEAD]]
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br i1 %x, label %loop, label %exit, !prof !5
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br i1 %x, label %loop, label %exit
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; CHECK-NEXT: float = 1.0, int = [[ENTRY]]
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!4 = metadata !{metadata !"branch_weights", i32 1, i32 1}
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!5 = metadata !{metadata !"branch_weights", i32 3, i32 1}
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; Two unrelated irreducible SCCs.
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define void @two_sccs(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'two_sccs':
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; CHECK-NEXT: block-frequency-info: two_sccs
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br i1 %x, label %a, label %b, !prof !6
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a:
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; CHECK-NEXT: a: float = 0.75,
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br i1 %x, label %a.left, label %a.right, !prof !7
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a.left:
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; CHECK-NEXT: a.left: float = 1.5,
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br i1 %x, label %a.right, label %exit, !prof !6
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a.right:
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; CHECK-NEXT: a.right: float = 1.5,
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br i1 %x, label %a.left, label %exit, !prof !6
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b:
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; CHECK-NEXT: b: float = 0.25,
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br i1 %x, label %b.left, label %b.right, !prof !7
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b.left:
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; CHECK-NEXT: b.left: float = 0.625,
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br i1 %x, label %b.right, label %exit, !prof !8
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b.right:
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; CHECK-NEXT: b.right: float = 0.625,
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br i1 %x, label %b.left, label %exit, !prof !8
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!6 = metadata !{metadata !"branch_weights", i32 3, i32 1}
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!7 = metadata !{metadata !"branch_weights", i32 1, i32 1}
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!8 = metadata !{metadata !"branch_weights", i32 4, i32 1}
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; A true loop inside irreducible control flow.
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define void @loop_inside_irreducible(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_inside_irreducible':
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; CHECK-NEXT: block-frequency-info: loop_inside_irreducible
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !9
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left:
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; CHECK-NEXT: left: float = 2.0,
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br i1 %x, label %right, label %exit, !prof !10
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right:
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; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]]
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br label %loop
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loop:
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; CHECK-NEXT: loop: float = 6.0,
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br i1 %x, label %loop, label %right.end, !prof !11
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right.end:
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; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]]
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br i1 %x, label %left, label %exit, !prof !10
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!9 = metadata !{metadata !"branch_weights", i32 1, i32 1}
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!10 = metadata !{metadata !"branch_weights", i32 3, i32 1}
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!11 = metadata !{metadata !"branch_weights", i32 2, i32 1}
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; Irreducible control flow in a branch that's in a true loop.
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define void @loop_around_branch_with_irreducible(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible':
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; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br label %loop
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loop:
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; CHECK-NEXT: loop: float = 2.0, int = [[LOOP:[0-9]+]]
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br i1 %x, label %normal, label %irreducible.entry, !prof !12
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normal:
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; CHECK-NEXT: normal: float = 1.5,
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br label %loop.end
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irreducible.entry:
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; CHECK-NEXT: irreducible.entry: float = 0.5, int = [[IRREDUCIBLE:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !13
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left:
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; CHECK-NEXT: left: float = 1.0,
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br i1 %x, label %right, label %irreducible.exit, !prof !12
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right:
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; CHECK-NEXT: right: float = 1.0,
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br i1 %x, label %left, label %irreducible.exit, !prof !12
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irreducible.exit:
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; CHECK-NEXT: irreducible.exit: float = 0.5, int = [[IRREDUCIBLE]]
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br label %loop.end
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loop.end:
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; CHECK-NEXT: loop.end: float = 2.0, int = [[LOOP]]
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br i1 %x, label %loop, label %exit, !prof !13
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!12 = metadata !{metadata !"branch_weights", i32 3, i32 1}
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!13 = metadata !{metadata !"branch_weights", i32 1, i32 1}
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; Irreducible control flow between two true loops.
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define void @loop_around_branch_with_irreducible_around_loop(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible_around_loop':
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; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible_around_loop
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br label %loop
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loop:
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; CHECK-NEXT: loop: float = 3.0, int = [[LOOP:[0-9]+]]
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br i1 %x, label %normal, label %irreducible, !prof !14
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normal:
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; CHECK-NEXT: normal: float = 2.0,
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br label %loop.end
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irreducible:
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; CHECK-NEXT: irreducible: float = 1.0,
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br i1 %x, label %left, label %right, !prof !15
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left:
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; CHECK-NEXT: left: float = 2.0,
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br i1 %x, label %right, label %loop.end, !prof !16
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right:
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; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]]
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br label %right.loop
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right.loop:
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; CHECK-NEXT: right.loop: float = 10.0,
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br i1 %x, label %right.loop, label %right.end, !prof !17
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right.end:
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; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]]
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br i1 %x, label %left, label %loop.end, !prof !16
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loop.end:
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; CHECK-NEXT: loop.end: float = 3.0, int = [[LOOP]]
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br i1 %x, label %loop, label %exit, !prof !14
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!14 = metadata !{metadata !"branch_weights", i32 2, i32 1}
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!15 = metadata !{metadata !"branch_weights", i32 1, i32 1}
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!16 = metadata !{metadata !"branch_weights", i32 3, i32 1}
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!17 = metadata !{metadata !"branch_weights", i32 4, i32 1}
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; An irreducible SCC with a non-header.
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define void @nonheader(i1 %x) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'nonheader':
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; CHECK-NEXT: block-frequency-info: nonheader
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !18
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left:
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; CHECK-NEXT: left: float = 1.0,
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br i1 %x, label %bottom, label %exit, !prof !19
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right:
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; CHECK-NEXT: right: float = 1.0,
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br i1 %x, label %bottom, label %exit, !prof !20
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bottom:
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; CHECK-NEXT: bottom: float = 1.0,
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br i1 %x, label %left, label %right, !prof !18
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!18 = metadata !{metadata !"branch_weights", i32 1, i32 1}
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!19 = metadata !{metadata !"branch_weights", i32 1, i32 3}
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!20 = metadata !{metadata !"branch_weights", i32 3, i32 1}
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; An irreducible SCC with an irreducible sub-SCC. In the current version of
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; -block-freq, this means an extra header.
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;
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; This testcases uses non-trivial branch weights. The CHECK statements here
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; will start to fail if we change -block-freq to be more accurate. Currently,
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; we expect left, right and top to be treated as equal headers.
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define void @nonentry_header(i1 %x, i2 %y) {
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; CHECK-LABEL: Printing analysis {{.*}} for function 'nonentry_header':
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; CHECK-NEXT: block-frequency-info: nonentry_header
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entry:
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; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
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br i1 %x, label %left, label %right, !prof !21
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left:
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; CHECK-NEXT: left: float = 3.0,
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br i1 %x, label %top, label %bottom, !prof !22
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right:
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; CHECK-NEXT: right: float = 3.0,
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br i1 %x, label %top, label %bottom, !prof !22
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top:
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; CHECK-NEXT: top: float = 3.0,
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switch i2 %y, label %exit [ i2 0, label %left
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i2 1, label %right
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i2 2, label %bottom ], !prof !23
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bottom:
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; CHECK-NEXT: bottom: float = 4.5,
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br label %top
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exit:
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; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
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ret void
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}
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!21 = metadata !{metadata !"branch_weights", i32 2, i32 1}
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!22 = metadata !{metadata !"branch_weights", i32 1, i32 1}
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!23 = metadata !{metadata !"branch_weights", i32 8, i32 1, i32 3, i32 12}
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