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Invoke SimplifyIndVar when we partially unroll a loop. Fixes PR10534.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137203 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick 2011-08-10 04:29:49 +00:00
parent bddb7f8210
commit 39f40299a6
3 changed files with 64 additions and 5 deletions
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5
lib/Transforms/Scalar/LoopUnrollPass.cpp
View File

@ -79,6 +79,7 @@ namespace {
AU.addPreservedID(LoopSimplifyID);
AU.addRequiredID(LCSSAID);
AU.addPreservedID(LCSSAID);
AU.addRequired<ScalarEvolution>();
AU.addPreserved<ScalarEvolution>();
// FIXME: Loop unroll requires LCSSA. And LCSSA requires dom info.
// If loop unroll does not preserve dom info then LCSSA pass on next
@ -187,12 +188,8 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
}
// Unroll the loop.
Function *F = L->getHeader()->getParent();
if (!UnrollLoop(L, Count, TripCount, TripMultiple, LI, &LPM))
return false;
// FIXME: Reconstruct dom info, because it is not preserved properly.
if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>())
DT->runOnFunction(*F);
return true;
}

25
lib/Transforms/Utils/LoopUnroll.cpp
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@ -29,6 +29,7 @@
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SimplifyIndVar.h"
using namespace llvm;
// TODO: Should these be here or in LoopUnroll?
@ -130,6 +131,9 @@ static BasicBlock *FoldBlockIntoPredecessor(BasicBlock *BB, LoopInfo* LI,
///
/// If a LoopPassManager is passed in, and the loop is fully removed, it will be
/// removed from the LoopPassManager as well. LPM can also be NULL.
///
/// This utility preserves LoopInfo. If DominatorTree or ScalarEvolution are
/// available it must also preseve those analyses.
bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
unsigned TripMultiple, LoopInfo *LI, LPPassManager *LPM) {
BasicBlock *Preheader = L->getLoopPreheader();
@ -163,7 +167,8 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
// Notify ScalarEvolution that the loop will be substantially changed,
// if not outright eliminated.
if (ScalarEvolution *SE = LPM->getAnalysisIfAvailable<ScalarEvolution>())
ScalarEvolution *SE = LPM->getAnalysisIfAvailable<ScalarEvolution>();
if (SE)
SE->forgetLoop(L);
if (TripCount != 0)
@ -374,6 +379,24 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
}
}
// FIXME: Reconstruct dom info, because it is not preserved properly.
// Incrementally updating domtree after loop unrolling woud be easy.
if (DominatorTree *DT = LPM->getAnalysisIfAvailable<DominatorTree>())
DT->runOnFunction(*L->getHeader()->getParent());
// Simplify any new induction variables in the partially unrolled loop.
if (SE && !CompletelyUnroll) {
SmallVector<WeakVH, 16> DeadInsts;
simplifyLoopIVs(L, SE, LPM, DeadInsts);
// Aggressively clean up dead instructions that simplifyLoopIVs already
// identified. Any remaining should be cleaned up below.
while (!DeadInsts.empty())
if (Instruction *Inst =
dyn_cast_or_null<Instruction>(&*DeadInsts.pop_back_val()))
RecursivelyDeleteTriviallyDeadInstructions(Inst);
}
// At this point, the code is well formed. We now do a quick sweep over the
// inserted code, doing constant propagation and dead code elimination as we
// go.

39
test/Transforms/LoopUnroll/2011-08-09-IVSimplify.ll Normal file
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@ -0,0 +1,39 @@
; RUN: opt -S < %s -loop-unroll -unroll-count=4 -disable-iv-rewrite | FileCheck %s
;
; Test induction variable simplify after loop unrolling. It should
; expose nice opportunities for GVN.
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f80:128:128-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
; PR10534: LoopUnroll not keeping canonical induction variable...
; CHECK: while.body.1:
; CHECK: %shr.1 = lshr i32 %bit_addr.addr.01, 5
; CHECK: %arrayidx.1 = getelementptr inbounds i32* %bitmap, i32 %shr.1
; CHECK: while.body.2:
; CHECK: %shr.2 = lshr i32 %bit_addr.addr.01, 5
; CHECK: %arrayidx.2 = getelementptr inbounds i32* %bitmap, i32 %shr.2
; CHECK: while.body.3:
; CHECK: %shr.3 = lshr i32 %bit_addr.addr.01, 5
; CHECK: %arrayidx.3 = getelementptr inbounds i32* %bitmap, i32 %shr.3
define void @FlipBit(i32* nocapture %bitmap, i32 %bit_addr, i32 %nbits) nounwind {
entry:
br label %while.body
while.body:
%nbits.addr.02 = phi i32 [ 128, %entry ], [ %dec, %while.body ]
%bit_addr.addr.01 = phi i32 [ 0, %entry ], [ %inc, %while.body ]
%dec = add i32 %nbits.addr.02, -1
%shr = lshr i32 %bit_addr.addr.01, 5
%rem = and i32 %bit_addr.addr.01, 31
%shl = shl i32 1, %rem
%arrayidx = getelementptr inbounds i32* %bitmap, i32 %shr
%tmp6 = load i32* %arrayidx, align 4
%xor = xor i32 %tmp6, %shl
store i32 %xor, i32* %arrayidx, align 4
%inc = add i32 %bit_addr.addr.01, 1
%tobool = icmp eq i32 %dec, 0
br i1 %tobool, label %while.end, label %while.body
while.end:
ret void
}