Index: include/llvm/Transforms/Utils/LoopUtils.h =================================================================== --- include/llvm/Transforms/Utils/LoopUtils.h +++ include/llvm/Transforms/Utils/LoopUtils.h @@ -433,7 +433,8 @@ SmallVectorImpl &, PredIteratorCache &, LoopInfo *, DominatorTree *, const TargetLibraryInfo *, - Loop *, AliasSetTracker *, LoopSafetyInfo *); + Loop *, AliasSetTracker *, LoopSafetyInfo *, + OptimizationRemarkEmitter *); /// \brief Computes safety information for a loop /// checks loop body & header for the possibility of may throw Index: lib/Transforms/Scalar/LICM.cpp =================================================================== --- lib/Transforms/Scalar/LICM.cpp +++ lib/Transforms/Scalar/LICM.cpp @@ -91,10 +91,11 @@ const Loop *CurLoop, AliasSetTracker *CurAST, const LoopSafetyInfo *SafetyInfo, OptimizationRemarkEmitter *ORE); -static bool isSafeToExecuteUnconditionally(const Instruction &Inst, +static bool isSafeToExecuteUnconditionally(Instruction &Inst, const DominatorTree *DT, const Loop *CurLoop, const LoopSafetyInfo *SafetyInfo, + OptimizationRemarkEmitter *ORE, const Instruction *CtxI = nullptr); static bool pointerInvalidatedByLoop(Value *V, uint64_t Size, const AAMDNodes &AAInfo, @@ -262,8 +263,9 @@ // Loop over all of the alias sets in the tracker object. for (AliasSet &AS : *CurAST) - Changed |= promoteLoopAccessesToScalars( - AS, ExitBlocks, InsertPts, PIC, LI, DT, TLI, L, CurAST, &SafetyInfo); + Changed |= + promoteLoopAccessesToScalars(AS, ExitBlocks, InsertPts, PIC, LI, DT, + TLI, L, CurAST, &SafetyInfo, ORE); // Once we have promoted values across the loop body we have to recursively // reform LCSSA as any nested loop may now have values defined within the @@ -403,7 +405,7 @@ if (CurLoop->hasLoopInvariantOperands(&I) && canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE) && isSafeToExecuteUnconditionally( - I, DT, CurLoop, SafetyInfo, + I, DT, CurLoop, SafetyInfo, ORE, CurLoop->getLoopPreheader()->getTerminator())) Changed |= hoist(I, DT, CurLoop, SafetyInfo, ORE); } @@ -778,15 +780,28 @@ /// Only sink or hoist an instruction if it is not a trapping instruction, /// or if the instruction is known not to trap when moved to the preheader. /// or if it is a trapping instruction and is guaranteed to execute. -static bool isSafeToExecuteUnconditionally(const Instruction &Inst, +static bool isSafeToExecuteUnconditionally(Instruction &Inst, const DominatorTree *DT, const Loop *CurLoop, const LoopSafetyInfo *SafetyInfo, + OptimizationRemarkEmitter *ORE, const Instruction *CtxI) { if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT)) return true; - return isGuaranteedToExecute(Inst, DT, CurLoop, SafetyInfo); + bool GuaranteedToExecute = + isGuaranteedToExecute(Inst, DT, CurLoop, SafetyInfo); + + if (!GuaranteedToExecute) { + auto *LI = dyn_cast(&Inst); + if (LI && CurLoop->isLoopInvariant(LI->getPointerOperand())) + ORE->emit(OptimizationRemarkMissed( + DEBUG_TYPE, "LoadWithLoopInvariantAddressCondExecuted", LI) + << "failed to hoist load with loop-invariant address " + "because load is conditionally executed"); + } + + return GuaranteedToExecute; } namespace { @@ -874,7 +889,8 @@ AliasSet &AS, SmallVectorImpl &ExitBlocks, SmallVectorImpl &InsertPts, PredIteratorCache &PIC, LoopInfo *LI, DominatorTree *DT, const TargetLibraryInfo *TLI, - Loop *CurLoop, AliasSetTracker *CurAST, LoopSafetyInfo *SafetyInfo) { + Loop *CurLoop, AliasSetTracker *CurAST, LoopSafetyInfo *SafetyInfo, + OptimizationRemarkEmitter *ORE) { // Verify inputs. assert(LI != nullptr && DT != nullptr && CurLoop != nullptr && CurAST != nullptr && SafetyInfo != nullptr && @@ -974,14 +990,14 @@ // If there is an non-load/store instruction in the loop, we can't promote // it. - if (const LoadInst *Load = dyn_cast(UI)) { + if (LoadInst *Load = dyn_cast(UI)) { assert(!Load->isVolatile() && "AST broken"); if (!Load->isSimple()) return Changed; if (!GuaranteedToExecute && !CanSpeculateLoad) CanSpeculateLoad = isSafeToExecuteUnconditionally( - *Load, DT, CurLoop, SafetyInfo, Preheader->getTerminator()); + *Load, DT, CurLoop, SafetyInfo, ORE, Preheader->getTerminator()); } else if (const StoreInst *Store = dyn_cast(UI)) { // Stores *of* the pointer are not interesting, only stores *to* the // pointer. Index: test/Transforms/LICM/opt-remarks-conditional-load.ll =================================================================== --- /dev/null +++ test/Transforms/LICM/opt-remarks-conditional-load.ll @@ -0,0 +1,47 @@ +; 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" + +; With the load from %p conditional, we can't optmize this and the remark +; should tell us about it. + +define void @test(i32* %array, i32* noalias %p) { +Entry: + br label %Loop + +Loop: + %j = phi i32 [ 0, %Entry ], [ %Next, %else] + %addr = getelementptr i32, i32* %array, i32 %j + %a = load i32, i32* %addr + %c = icmp eq i32 %a, 0 + br i1 %c, label %then, label %else + +then: +; CHECK: remark: /tmp/kk.c:2:20: failed to hoist load with loop-invariant address because load is conditionally executed + %b = load i32, i32* %p, !dbg !8 + %a2 = add i32 %a, %b + store i32 %a2, i32* %addr + br label %else + +else: + %Next = add i32 %j, 1 + %cond = icmp eq i32 %Next, 0 + br i1 %cond, label %Out, label %Loop + +Out: + ret void +} + +!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)