diff options
| -rw-r--r-- | llvm/lib/CodeGen/CodeGenPrepare.cpp | 45 |
1 files changed, 28 insertions, 17 deletions
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp index e9611392058..a6a4ea2aff9 100644 --- a/llvm/lib/CodeGen/CodeGenPrepare.cpp +++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp @@ -1159,19 +1159,33 @@ static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI, return SinkCast(CI); } -static void replaceMathCmpWithIntrinsic(BinaryOperator *BO, CmpInst *Cmp, - Instruction *InsertPt, +static bool replaceMathCmpWithIntrinsic(BinaryOperator *BO, CmpInst *Cmp, Intrinsic::ID IID) { + // We allow matching the canonical IR (add X, C) back to (usubo X, -C). Value *Arg0 = BO->getOperand(0); Value *Arg1 = BO->getOperand(1); - - // We allow matching the canonical IR (add X, C) back to (usubo X, -C). if (BO->getOpcode() == Instruction::Add && IID == Intrinsic::usub_with_overflow) { assert(isa<Constant>(Arg1) && "Unexpected input for usubo"); Arg1 = ConstantExpr::getNeg(cast<Constant>(Arg1)); } + Instruction *InsertPt; + if (BO->hasOneUse() && BO->user_back() == Cmp) { + // If the math is only used by the compare, insert at the compare to keep + // the condition in the same block as its users. (CGP aggressively sinks + // compares to help out SDAG.) + InsertPt = Cmp; + } else { + // The math and compare may be independent instructions. Check dominance to + // determine the insertion point for the intrinsic. + DominatorTree DT(*BO->getFunction()); + bool MathDominates = DT.dominates(BO, Cmp); + if (!MathDominates && !DT.dominates(Cmp, BO)) + return false; + InsertPt = MathDominates ? cast<Instruction>(BO) : cast<Instruction>(Cmp); + } + IRBuilder<> Builder(InsertPt); Value *MathOV = Builder.CreateBinaryIntrinsic(IID, Arg0, Arg1); Value *Math = Builder.CreateExtractValue(MathOV, 0, "math"); @@ -1180,12 +1194,13 @@ static void replaceMathCmpWithIntrinsic(BinaryOperator *BO, CmpInst *Cmp, Cmp->replaceAllUsesWith(OV); BO->eraseFromParent(); Cmp->eraseFromParent(); + return true; } /// Try to combine the compare into a call to the llvm.uadd.with.overflow /// intrinsic. Return true if any changes were made. static bool combineToUAddWithOverflow(CmpInst *Cmp, const TargetLowering &TLI, - const DataLayout &DL) { + const DataLayout &DL, bool &ModifiedDT) { Value *A, *B; BinaryOperator *Add; if (!match(Cmp, m_UAddWithOverflow(m_Value(A), m_Value(B), m_BinOp(Add)))) @@ -1208,9 +1223,11 @@ static bool combineToUAddWithOverflow(CmpInst *Cmp, const TargetLowering &TLI, assert(*Add->user_begin() == Cmp && "expected!"); #endif - Instruction *InPt = Add->hasOneUse() ? cast<Instruction>(Cmp) - : cast<Instruction>(Add); - replaceMathCmpWithIntrinsic(Add, Cmp, InPt, Intrinsic::uadd_with_overflow); + if (!replaceMathCmpWithIntrinsic(Add, Cmp, Intrinsic::uadd_with_overflow)) + return false; + + // Reset callers - do not crash by iterating over a dead instruction. + ModifiedDT = true; return true; } @@ -1263,15 +1280,9 @@ static bool combineToUSubWithOverflow(CmpInst *Cmp, const TargetLowering &TLI, TLI.getValueType(DL, Sub->getType()))) return false; - // Pattern matched and profitability checked. Check dominance to determine the - // insertion point for an intrinsic that replaces the subtract and compare. - DominatorTree DT(*Sub->getFunction()); - bool SubDominates = DT.dominates(Sub, Cmp); - if (!SubDominates && !DT.dominates(Cmp, Sub)) + if (!replaceMathCmpWithIntrinsic(Sub, Cmp, Intrinsic::usub_with_overflow)) return false; - Instruction *InPt = SubDominates ? cast<Instruction>(Sub) - : cast<Instruction>(Cmp); - replaceMathCmpWithIntrinsic(Sub, Cmp, InPt, Intrinsic::usub_with_overflow); + // Reset callers - do not crash by iterating over a dead instruction. ModifiedDT = true; return true; @@ -1348,7 +1359,7 @@ static bool optimizeCmp(CmpInst *Cmp, const TargetLowering &TLI, if (sinkCmpExpression(Cmp, TLI)) return true; - if (combineToUAddWithOverflow(Cmp, TLI, DL)) + if (combineToUAddWithOverflow(Cmp, TLI, DL, ModifiedDT)) return true; if (combineToUSubWithOverflow(Cmp, TLI, DL, ModifiedDT)) |
