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Run LICM pass after loop unrolling pass.

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Runtime unrollng will introduce a runtime check in loop prologue.
If the unrolled loop is a inner loop, then the proglogue will be inside
the outer loop. LICM pass can help to promote the runtime check out if
the checked value is loop invariant.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231630 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Kevin Qin 2015-03-09 06:14:07 +00:00
parent 4c8f5afd99
commit 3836dd0315
3 changed files with 53 additions and 7 deletions
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8
lib/Transforms/IPO/PassManagerBuilder.cpp
View File

@ -364,8 +364,14 @@ void PassManagerBuilder::populateModulePassManager(
MPM.add(createCFGSimplificationPass());
MPM.add(createInstructionCombiningPass());
if (!DisableUnrollLoops)
if (!DisableUnrollLoops) {
MPM.add(createLoopUnrollPass()); // Unroll small loops
// Runtime unrollng will introduce runtime check in loop prologue. If the
// unrolled loop is a inner loop, then the prologue will be inside the
// outer loop. LICM pass can help to promote the runtime check out if the
// checked value is loop invariant.
MPM.add(createLICMPass());
}
// After vectorization and unrolling, assume intrinsics may tell us more
// about pointer alignments.

9
lib/Transforms/Utils/LoopUnrollRuntime.cpp
View File

@ -142,7 +142,7 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
BasicBlock *InsertTop, BasicBlock *InsertBot,
std::vector<BasicBlock *> &NewBlocks,
LoopBlocksDFS &LoopBlocks, ValueToValueMapTy &VMap,
LoopInfo *LI) {
LoopInfo *LI, LPPassManager *LPM) {
BasicBlock *Preheader = L->getLoopPreheader();
BasicBlock *Header = L->getHeader();
BasicBlock *Latch = L->getLoopLatch();
@ -153,10 +153,7 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
Loop *ParentLoop = L->getParentLoop();
if (!UnrollProlog) {
NewLoop = new Loop();
if (ParentLoop)
ParentLoop->addChildLoop(NewLoop);
else
LI->addTopLevelLoop(NewLoop);
LPM->insertLoop(NewLoop, ParentLoop);
}
// For each block in the original loop, create a new copy,
@ -390,7 +387,7 @@ bool llvm::UnrollRuntimeLoopProlog(Loop *L, unsigned Count, LoopInfo *LI,
// the loop, otherwise we create a cloned loop to execute the extra
// iterations. This function adds the appropriate CFG connections.
CloneLoopBlocks(L, ModVal, UnrollPrologue, PH, PEnd, NewBlocks, LoopBlocks,
VMap, LI);
VMap, LI, LPM);
// Insert the cloned blocks into function just before the original loop
F->getBasicBlockList().splice(PEnd, F->getBasicBlockList(), NewBlocks[0],

43
test/Transforms/LoopUnroll/runtime-loop4.ll Normal file
View File

@ -0,0 +1,43 @@
; RUN: opt < %s -S -O2 -unroll-runtime=true | FileCheck %s
; Check runtime unrolling prologue can be promoted by LICM pass.
; CHECK: entry:
; CHECK: %xtraiter
; CHECK: %lcmp.mod
; CHECK: loop1:
; CHECK: br i1 %lcmp.mod
; CHECK: loop2.prol:
define void @unroll(i32 %iter, i32* %addr1, i32* %addr2) nounwind {
entry:
br label %loop1
loop1:
%iv1 = phi i32 [ 0, %entry ], [ %inc1, %loop1.latch ]
%offset1 = getelementptr i32, i32* %addr1, i32 %iv1
store i32 %iv1, i32* %offset1, align 4
br label %loop2.header
loop2.header:
br label %loop2
loop2:
%iv2 = phi i32 [ 0, %loop2.header ], [ %inc2, %loop2 ]
%offset2 = getelementptr i32, i32* %addr2, i32 %iv2
store i32 %iv2, i32* %offset2, align 4
%inc2 = add i32 %iv2, 1
%exitcnd2 = icmp uge i32 %inc2, %iter
br i1 %exitcnd2, label %exit2, label %loop2
exit2:
br label %loop1.latch
loop1.latch:
%inc1 = add i32 %iv1, 1
%exitcnd1 = icmp uge i32 %inc1, 1024
br i1 %exitcnd1, label %exit, label %loop1
exit:
ret void
}