Index: include/llvm/Transforms/Utils/LoopUtils.h =================================================================== --- include/llvm/Transforms/Utils/LoopUtils.h +++ include/llvm/Transforms/Utils/LoopUtils.h @@ -483,10 +483,11 @@ /// If SafetyInfo is not null, we are checking for hoisting/sinking /// instructions from loop body to preheader/exit. Check if the instruction /// can execute speculatively. -/// +/// If \p ORE is set use it to emit optimization remarks. bool canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT, Loop *CurLoop, AliasSetTracker *CurAST, - LoopSafetyInfo *SafetyInfo); + LoopSafetyInfo *SafetyInfo, + OptimizationRemarkEmitter *ORE = nullptr); } #endif Index: lib/Transforms/Scalar/LICM.cpp =================================================================== --- lib/Transforms/Scalar/LICM.cpp +++ lib/Transforms/Scalar/LICM.cpp @@ -348,7 +348,7 @@ // operands of the instruction are loop invariant. // if (isNotUsedInLoop(I, CurLoop, SafetyInfo) && - canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo)) { + canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE)) { ++II; Changed |= sink(I, LI, DT, CurLoop, CurAST, SafetyInfo, ORE); } @@ -402,7 +402,7 @@ // is safe to hoist the instruction. // if (CurLoop->hasLoopInvariantOperands(&I) && - canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo) && + canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE) && isSafeToExecuteUnconditionally( I, DT, CurLoop, SafetyInfo, CurLoop->getLoopPreheader()->getTerminator())) @@ -451,7 +451,8 @@ bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT, Loop *CurLoop, AliasSetTracker *CurAST, - LoopSafetyInfo *SafetyInfo) { + LoopSafetyInfo *SafetyInfo, + OptimizationRemarkEmitter *ORE) { // Loads have extra constraints we have to verify before we can hoist them. if (LoadInst *LI = dyn_cast(&I)) { if (!LI->isUnordered()) @@ -472,7 +473,17 @@ AAMDNodes AAInfo; LI->getAAMetadata(AAInfo); - return !pointerInvalidatedByLoop(LI->getOperand(0), Size, AAInfo, CurAST); + bool Invalidated = + pointerInvalidatedByLoop(LI->getOperand(0), Size, AAInfo, CurAST); + // Check loop-invariant address because this may also be a sinkable load + // whose address is not necessarily loop-invariant. + if (ORE && Invalidated && CurLoop->isLoopInvariant(LI->getPointerOperand())) + ORE->emit(OptimizationRemarkMissed( + DEBUG_TYPE, "LoadWithLoopInvariantAddressInvalidated", LI) + << "failed to move load with loop-invariant address " + "because the loop may invalidate its value"); + + return !Invalidated; } else if (CallInst *CI = dyn_cast(&I)) { // Don't sink or hoist dbg info; it's legal, but not useful. if (isa(I)) Index: test/Transforms/LICM/opt-remarks-intervening-store.ll =================================================================== --- /dev/null +++ test/Transforms/LICM/opt-remarks-intervening-store.ll @@ -0,0 +1,67 @@ +; RUN: opt < %s -licm -pass-remarks-missed=licm -o /dev/null 2>&1 | FileCheck %s +; RUN: opt -aa-pipeline=basic-aa -passes='require,require,require,require,loop(licm)' %s -o /dev/null -pass-remarks-missed=licm 2>&1 | FileCheck %s +target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" + +; Without the noalias on %p, we can't optmize this and the remark should tell +; us about it. + +define void @test(i32* %array, i32* %p) { +Entry: + br label %Loop + +Loop: + %j = phi i32 [ 0, %Entry ], [ %Next, %Loop ] + %addr = getelementptr i32, i32* %array, i32 %j + %a = load i32, i32* %addr +; CHECK: remark: /tmp/kk.c:2:20: failed to move load with loop-invariant address because the loop may invalidate its value + %b = load i32, i32* %p, !dbg !8 + %a2 = add i32 %a, %b + store i32 %a2, i32* %addr + %Next = add i32 %j, 1 + %cond = icmp eq i32 %Next, 0 + br i1 %cond, label %Out, label %Loop + +Out: + ret void +} + +; This illustrates why we need to check loop-invariance before issuing this +; remark. + +define i32 @invalidated_load_with_non_loop_invariant_address(i32* %array, i32* %array2) { +Entry: + br label %Loop + +Loop: + %j = phi i32 [ 0, %Entry ], [ %Next, %Loop ] + +; CHECK-NOT: /tmp/kk.c:3:20: {{.*}} loop-invariant + %addr = getelementptr i32, i32* %array, i32 %j + %a = load i32, i32* %addr, !dbg !9 + + %addr2 = getelementptr i32, i32* %array2, i32 %j + store i32 %j, i32* %addr2 + + %Next = add i32 %j, 1 + %cond = icmp eq i32 %Next, 0 + br i1 %cond, label %Out, label %Loop + +Out: + %a2 = phi i32 [ %a, %Loop ] + ret i32 %a2 +} + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!3, !4} +!llvm.ident = !{!5} + +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: NoDebug, enums: !2) +!1 = !DIFile(filename: "/tmp/kk.c", directory: "/tmp") +!2 = !{} +!3 = !{i32 2, !"Debug Info Version", i32 3} +!4 = !{i32 1, !"PIC Level", i32 2} +!5 = !{!"clang version 3.9.0 "} +!6 = distinct !DISubprogram(name: "success", scope: !1, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2) +!7 = !DISubroutineType(types: !2) +!8 = !DILocation(line: 2, column: 20, scope: !6) +!9 = !DILocation(line: 3, column: 20, scope: !6)