diff options
| -rw-r--r-- | llvm/lib/Transforms/Utils/SimplifyIndVar.cpp | 30 | ||||
| -rw-r--r-- | llvm/test/Transforms/IndVarSimplify/constant-fold.ll | 47 | ||||
| -rw-r--r-- | llvm/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll | 2 |
3 files changed, 78 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp index 5228f067ae1..cef8fe1a614 100644 --- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp @@ -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(Instruction *UseInst, 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(PHINode *CurrIV, IVVisitor *V) { // 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"); diff --git a/llvm/test/Transforms/IndVarSimplify/constant-fold.ll b/llvm/test/Transforms/IndVarSimplify/constant-fold.ll new file mode 100644 index 00000000000..a35349aa1f5 --- /dev/null +++ b/llvm/test/Transforms/IndVarSimplify/constant-fold.ll @@ -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 diff --git a/llvm/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll b/llvm/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll index 6629420df55..ec1ccffbc5c 100644 --- a/llvm/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll +++ b/llvm/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll @@ -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 |
