[llvm] r314266 - [SimplifyIndVar] Constant fold IV users
Hongbin Zheng via llvm-commits
llvm-commits at lists.llvm.org
Fri Sep 29 09:41:00 PDT 2017
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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