[llvm] r314266 - [SimplifyIndVar] Constant fold IV users
NAKAMURA Takumi via llvm-commits
llvm-commits at lists.llvm.org
Sat Sep 30 16:25:36 PDT 2017
Confirmed. Thanks!
On Sat, Sep 30, 2017 at 1:41 AM Hongbin Zheng <etherzhhb at gmail.com> wrote:
> r314531 should fix this.
>
> Thanks
> hongbin
>
> On Fri, Sep 29, 2017 at 5:04 AM, NAKAMURA Takumi <geek4civic at gmail.com>
> wrote:
>
>> It crashed during LTO.
>> http://bb.pgr.jp/builders/clang-3stage-x86_64-linux/builds/38
>>
>> Reduced testscase attached. "opt -indvars" should reproduce.
>>
>> On Wed, Sep 27, 2017 at 12:13 PM Hongbin Zheng via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: ether
>>> Date: Tue Sep 26 20:11:46 2017
>>> New Revision: 314266
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=314266&view=rev
>>> Log:
>>> [SimplifyIndVar] Constant fold IV users
>>>
>>> This patch tries to transform cases like:
>>>
>>> for (unsigned i = 0; i < N; i += 2) {
>>> bool c0 = (i & 0x1) == 0;
>>> bool c1 = ((i + 1) & 0x1) == 1;
>>> }
>>> To
>>>
>>> for (unsigned i = 0; i < N; i += 2) {
>>> bool c0 = true;
>>> bool c1 = true;
>>> }
>>>
>>> This commit also update
>>> test/Transforms/IndVarSimplify/replace-srem-by-urem.ll to prevent constant
>>> folding.
>>>
>>> Differential Revision: https://reviews.llvm.org/D38272
>>>
>>> Added:
>>> llvm/trunk/test/Transforms/IndVarSimplify/constant-fold.ll
>>> Modified:
>>> llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
>>> llvm/trunk/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll
>>>
>>> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp?rev=314266&r1=314265&r2=314266&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp Tue Sep 26
>>> 20:11:46 2017
>>> @@ -35,6 +35,7 @@ using namespace llvm;
>>>
>>> STATISTIC(NumElimIdentity, "Number of IV identities eliminated");
>>> STATISTIC(NumElimOperand, "Number of IV operands folded into a use");
>>> +STATISTIC(NumFoldedUser, "Number of IV users folded into a constant");
>>> STATISTIC(NumElimRem , "Number of IV remainder operations
>>> eliminated");
>>> STATISTIC(
>>> NumSimplifiedSDiv,
>>> @@ -76,6 +77,7 @@ namespace {
>>> Value *foldIVUser(Instruction *UseInst, Instruction *IVOperand);
>>>
>>> bool eliminateIdentitySCEV(Instruction *UseInst, Instruction
>>> *IVOperand);
>>> + bool foldConstantSCEV(Instruction *UseInst);
>>>
>>> bool eliminateOverflowIntrinsic(CallInst *CI);
>>> bool eliminateIVUser(Instruction *UseInst, Instruction *IVOperand);
>>> @@ -534,6 +536,30 @@ bool SimplifyIndvar::eliminateIVUser(Ins
>>> return false;
>>> }
>>>
>>> +/// Replace the UseInst with a constant if possible
>>> +bool SimplifyIndvar::foldConstantSCEV(Instruction *I) {
>>> + if (!SE->isSCEVable(I->getType()))
>>> + return false;
>>> +
>>> + // Get the symbolic expression for this instruction.
>>> + const SCEV *S = SE->getSCEV(I);
>>> +
>>> + const Loop *L = LI->getLoopFor(I->getParent());
>>> + S = SE->getSCEVAtScope(S, L);
>>> +
>>> + if (auto *C = dyn_cast<SCEVConstant>(S)) {
>>> + I->replaceAllUsesWith(C->getValue());
>>> + DEBUG(dbgs() << "INDVARS: Replace IV user: " << *I
>>> + << " with constant: " << *C << '\n');
>>> + ++NumFoldedUser;
>>> + Changed = true;
>>> + DeadInsts.emplace_back(I);
>>> + return true;
>>> + }
>>> +
>>> + return false;
>>> +}
>>> +
>>> /// Eliminate any operation that SCEV can prove is an identity function.
>>> bool SimplifyIndvar::eliminateIdentitySCEV(Instruction *UseInst,
>>> Instruction *IVOperand) {
>>> @@ -741,6 +767,10 @@ void SimplifyIndvar::simplifyUsers(PHINo
>>> // Bypass back edges to avoid extra work.
>>> if (UseInst == CurrIV) continue;
>>>
>>> + // Try to replace UseInst with a constant before any other
>>> simplifications
>>> + if (foldConstantSCEV(UseInst))
>>> + continue;
>>> +
>>> Instruction *IVOperand = UseOper.second;
>>> for (unsigned N = 0; IVOperand; ++N) {
>>> assert(N <= Simplified.size() && "runaway iteration");
>>>
>>> Added: llvm/trunk/test/Transforms/IndVarSimplify/constant-fold.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/constant-fold.ll?rev=314266&view=auto
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/Transforms/IndVarSimplify/constant-fold.ll (added)
>>> +++ llvm/trunk/test/Transforms/IndVarSimplify/constant-fold.ll Tue Sep
>>> 26 20:11:46 2017
>>> @@ -0,0 +1,47 @@
>>> +; RUN: opt -indvars -S < %s | FileCheck %s
>>> +
>>> +define void @test0(i32* %x) {
>>> +entry:
>>> + br label %for.inc
>>> +
>>> +for.inc: ; preds = %for.inc,
>>> %entry
>>> + %i.01 = phi i32 [ 0, %entry ], [ %add, %for.inc ]
>>> + %and = and i32 %i.01, 3
>>> + %cmp1 = icmp eq i32 %and, 0
>>> + %cond = select i1 %cmp1, i32 0, i32 1
>>> + store i32 %cond, i32* %x, align 4
>>> + %add = add i32 %i.01, 4
>>> + %cmp = icmp ult i32 %add, 8
>>> + br i1 %cmp, label %for.inc, label %for.end
>>> +
>>> +for.end: ; preds = %for.inc
>>> + ret void
>>> +}
>>> +
>>> +; Should fold the condition of the select into constant
>>> +; CHECK-LABEL: void @test
>>> +; CHECK: icmp eq i32 0, 0
>>> +
>>> +define void @test1(i32* %a) {
>>> +entry:
>>> + br label %for.body
>>> +
>>> +for.body: ; preds = %entry,
>>> %for.body
>>> + %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
>>> + %mul = mul nsw i32 %i.01, 64
>>> + %rem = srem i32 %mul, 8
>>> + %idxprom = sext i32 %rem to i64
>>> + %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
>>> + store i32 %i.01, i32* %arrayidx, align 4
>>> + %inc = add nsw i32 %i.01, 1
>>> + %cmp = icmp slt i32 %inc, 64
>>> + br i1 %cmp, label %for.body, label %for.end
>>> +
>>> +for.end: ; preds = %for.body
>>> + ret void
>>> +}
>>> +
>>> +; Should fold the rem since %mul is multiple of 8
>>> +; CHECK-LABEL: @test1(
>>> +; CHECK-NOT: rem
>>> +; CHECK: sext i32 0 to i64
>>>
>>> Modified:
>>> llvm/trunk/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll?rev=314266&r1=314265&r2=314266&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll
>>> (original)
>>> +++ llvm/trunk/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll
>>> Tue Sep 26 20:11:46 2017
>>> @@ -71,7 +71,7 @@ entry:
>>> for.body: ; preds = %entry,
>>> %for.body
>>> %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
>>> %mul = mul nsw i32 %i.01, 64
>>> - %rem = srem i32 %mul, 8
>>> + %rem = srem i32 %mul, 7
>>> ; CHECK: urem
>>> ; CHECK-NOT: srem
>>> %idxprom = sext i32 %rem to i64
>>>
>>>
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>>
>
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