diff options
| -rw-r--r-- | lib/Transforms/InstCombine/InstructionCombining.cpp | 59 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/gepphigep.ll | 56 |
2 files changed, 115 insertions, 0 deletions
diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp index 4c36887f62..35b4889a83 100644 --- a/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -1220,6 +1220,65 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { if (MadeChange) return &GEP; } + // Check to see if the inputs to the PHI node are getelementptr instructions. + if (PHINode *PN = dyn_cast<PHINode>(PtrOp)) { + GetElementPtrInst *Op1 = dyn_cast<GetElementPtrInst>(PN->getOperand(0)); + if (!Op1) + return nullptr; + + signed DI = -1; + + for (auto I = PN->op_begin()+1, E = PN->op_end(); I !=E; ++I) { + GetElementPtrInst *Op2 = dyn_cast<GetElementPtrInst>(*I); + if (!Op2 || Op1->getNumOperands() != Op1->getNumOperands()) + return nullptr; + + for (unsigned J = 0, F = Op1->getNumOperands(); J != F; ++J) { + if (Op1->getOperand(J) != Op2->getOperand(J)) { + if (DI == -1) { + // We have not seen any differences yet in the GEPs feeding the + // PHI yet, so we record this one. + DI = J; + } else { + // The GEP is different by more than one input. While this could be + // extended to support GEPs that vary by more than one variable it + // doesn't make sense since it greatly increases the complexity and + // would result in an R+R+R addressing mode which no backend + // directly supports and would need to be broken into several + // simpler instructions anyway. + return nullptr; + } + } + } + } + + GetElementPtrInst *NewGEP = dyn_cast<GetElementPtrInst>(Op1->clone()); + + if (DI == -1) { + // All the GEPs feeding the PHI are identical. Clone one down into our + // BB so that it can be merged with the current GEP. + GEP.getParent()->getInstList().insert(GEP.getParent()->getFirstNonPHI(), + NewGEP); + } else { + // All the GEPs feeding the PHI differ at a single offset. Clone a GEP + // into the current block so it can be merged, and create a new PHI to + // set that index. + PHINode *NewPN = Builder->CreatePHI(Op1->getOperand(DI)->getType(), + PN->getNumOperands()); + for (auto &I : PN->operands()) + NewPN->addIncoming(dyn_cast<GEPOperator>(I)->getOperand(DI), + PN->getIncomingBlock(I)); + + NewGEP->setOperand(DI, NewPN); + GEP.getParent()->getInstList().insert(GEP.getParent()->getFirstNonPHI(), + NewGEP); + NewGEP->setOperand(DI, NewPN); + } + + GEP.setOperand(0, NewGEP); + PtrOp = NewGEP; + } + // Combine Indices - If the source pointer to this getelementptr instruction // is a getelementptr instruction, combine the indices of the two // getelementptr instructions into a single instruction. diff --git a/test/Transforms/InstCombine/gepphigep.ll b/test/Transforms/InstCombine/gepphigep.ll new file mode 100644 index 0000000000..b724ac2ece --- /dev/null +++ b/test/Transforms/InstCombine/gepphigep.ll @@ -0,0 +1,56 @@ +; RUN: opt -instcombine -S < %s | FileCheck %s + +%struct1 = type { %struct2*, i32, i32, i32 } +%struct2 = type { i32, i32 } + +define i32 @test1(%struct1* %dm, i1 %tmp4, i64 %tmp9, i64 %tmp19) { +bb: + %tmp = getelementptr inbounds %struct1* %dm, i64 0, i32 0 + %tmp1 = load %struct2** %tmp, align 8 + br i1 %tmp4, label %bb1, label %bb2 + +bb1: + %tmp10 = getelementptr inbounds %struct2* %tmp1, i64 %tmp9 + %tmp11 = getelementptr inbounds %struct2* %tmp10, i64 0, i32 0 + store i32 0, i32* %tmp11, align 4 + br label %bb3 + +bb2: + %tmp20 = getelementptr inbounds %struct2* %tmp1, i64 %tmp19 + %tmp21 = getelementptr inbounds %struct2* %tmp20, i64 0, i32 0 + store i32 0, i32* %tmp21, align 4 + br label %bb3 + +bb3: + %phi = phi %struct2* [ %tmp10, %bb1 ], [ %tmp20, %bb2 ] + %tmp24 = getelementptr inbounds %struct2* %phi, i64 0, i32 1 + %tmp25 = load i32* %tmp24, align 4 + ret i32 %tmp25 + +; CHECK-LABEL: @test1( +; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp9, i32 0 +; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp19, i32 0 +; CHECK: %[[PHI:[0-9A-Za-z]+]] = phi i64 [ %tmp9, %bb1 ], [ %tmp19, %bb2 ] +; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %[[PHI]], i32 1 +} + +define i32 @test2(%struct1* %dm, i1 %tmp4, i64 %tmp9, i64 %tmp19) { +bb: + %tmp = getelementptr inbounds %struct1* %dm, i64 0, i32 0 + %tmp1 = load %struct2** %tmp, align 8 + %tmp10 = getelementptr inbounds %struct2* %tmp1, i64 %tmp9 + %tmp11 = getelementptr inbounds %struct2* %tmp10, i64 0, i32 0 + store i32 0, i32* %tmp11, align 4 + %tmp20 = getelementptr inbounds %struct2* %tmp1, i64 %tmp19 + %tmp21 = getelementptr inbounds %struct2* %tmp20, i64 0, i32 0 + store i32 0, i32* %tmp21, align 4 + %tmp24 = getelementptr inbounds %struct2* %tmp10, i64 0, i32 1 + %tmp25 = load i32* %tmp24, align 4 + ret i32 %tmp25 + +; CHECK-LABEL: @test2( +; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp9, i32 0 +; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp19, i32 0 +; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp9, i32 1 +} + |