diff --git a/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp b/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp --- a/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp +++ b/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp @@ -65,6 +65,7 @@ #include "llvm/Analysis/GlobalsModRef.h" #include "llvm/Analysis/ValueTracking.h" #include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" #include "llvm/IR/Module.h" #include "llvm/IR/Operator.h" #include "llvm/InitializePasses.h" @@ -254,9 +255,25 @@ bool SpeculativeExecutionPass::considerHoistingFromTo( BasicBlock &FromBlock, BasicBlock &ToBlock) { SmallPtrSet NotHoisted; - const auto AllPrecedingUsesFromBlockHoisted = [&NotHoisted](User *U) { - for (Value* V : U->operand_values()) { - if (Instruction *I = dyn_cast(V)) { + const auto AllPrecedingUsesFromBlockHoisted = [&NotHoisted](const User *U) { + // Debug variable has special operand to check it's not hoisted. + if (const auto *DVI = dyn_cast(U)) { + if (const auto *I = + dyn_cast_or_null(DVI->getVariableLocation())) + if (NotHoisted.count(I) == 0) + return true; + return false; + } + + // Usially debug label instrinsic corresponds to label in LLVM IR. In these + // cases we should not move it here. + // TODO: Possible special processing needed to detect it is related to a + // hoisted instruction. + if (isa(U)) + return false; + + for (const Value *V : U->operand_values()) { + if (const Instruction *I = dyn_cast(V)) { if (NotHoisted.count(I) > 0) return false; } @@ -265,7 +282,8 @@ }; unsigned TotalSpeculationCost = 0; - for (auto& I : FromBlock) { + unsigned NotHoistedInstCount = 0; + for (const auto &I : FromBlock) { const unsigned Cost = ComputeSpeculationCost(&I, *TTI); if (Cost != UINT_MAX && isSafeToSpeculativelyExecute(&I) && AllPrecedingUsesFromBlockHoisted(&I)) { @@ -273,9 +291,14 @@ if (TotalSpeculationCost > SpecExecMaxSpeculationCost) return false; // too much to hoist } else { - NotHoisted.insert(&I); - if (NotHoisted.size() > SpecExecMaxNotHoisted) + // If the instruction cannot be hoisted but has zero cost suppose it's + // a special case e.g. debug info instrinsics that should not be counted + // for threshold. + if (Cost) + NotHoistedInstCount++; + if (NotHoistedInstCount > SpecExecMaxNotHoisted) return false; // too much left behind + NotHoisted.insert(&I); } } diff --git a/llvm/test/Transforms/SpeculativeExecution/PR46267.ll b/llvm/test/Transforms/SpeculativeExecution/PR46267.ll new file mode 100644 --- /dev/null +++ b/llvm/test/Transforms/SpeculativeExecution/PR46267.ll @@ -0,0 +1,63 @@ +; RUN: opt < %s -S -speculative-execution | FileCheck %s +; RUN: opt < %s -S -passes='speculative-execution' | FileCheck %s + +define void @f(i32 %i) { +entry: +; CHECK-LABEL: @f( +; CHECK: %a2 = add i32 %i, 0 +; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 %a2 + br i1 undef, label %land.rhs, label %land.end + +land.rhs: ; preds = %entry +; CHECK: land.rhs: +; CHECK-NEXT: call void @llvm.dbg.label +; CHECK-NEXT: %x = alloca i32, align 4 +; CHECK-NEXT: call void @llvm.dbg.addr(metadata i32* %x +; CHECK-NEXT: %y = alloca i32, align 4 +; CHECK-NEXT: call void @llvm.dbg.declare(metadata i32* %y +; CHECK-NEXT: %a0 = load i32, i32* undef, align 1 +; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 %a0 + call void @llvm.dbg.label(metadata !11), !dbg !10 + %x = alloca i32, align 4 + call void @llvm.dbg.addr(metadata i32* %x, metadata !12, metadata !DIExpression()), !dbg !10 + %y = alloca i32, align 4 + call void @llvm.dbg.declare(metadata i32* %y, metadata !14, metadata !DIExpression()), !dbg !10 + + %a0 = load i32, i32* undef, align 1 + call void @llvm.dbg.value(metadata i32 %a0, metadata !9, metadata !DIExpression()), !dbg !10 + + %a2 = add i32 %i, 0 + call void @llvm.dbg.value(metadata i32 %a2, metadata !13, metadata !DIExpression()), !dbg !10 + + br label %land.end + +land.end: ; preds = %land.rhs, %entry + ret void +} + +; Function Attrs: nounwind readnone speculatable willreturn +declare void @llvm.dbg.value(metadata, metadata, metadata) #1 +declare void @llvm.dbg.label(metadata) +declare void @llvm.dbg.declare(metadata, metadata, metadata) +declare void @llvm.dbg.addr(metadata, metadata, metadata) + +attributes #1 = { nounwind readnone speculatable willreturn } + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!5} + +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 11.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, splitDebugInlining: false, nameTableKind: None) +!1 = !DIFile(filename: "foo.c", directory: "/bar") +!2 = !{} +!3 = !{!4} +!4 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed) +!5 = !{i32 2, !"Debug Info Version", i32 3} +!6 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !7, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2) +!7 = !DISubroutineType(types: !8) +!8 = !{null} +!9 = !DILocalVariable(name: "a0", scope: !6, file: !1, line: 3, type: !4) +!10 = !DILocation(line: 0, scope: !6) +!11 = !DILabel(scope: !6, name: "label", file: !1, line: 1) +!12 = !DILocalVariable(name: "x", scope: !6, file: !1, line: 3, type: !4) +!13 = !DILocalVariable(name: "a2", scope: !6, file: !1, line: 3, type: !4) +!14 = !DILocalVariable(name: "y", scope: !6, file: !1, line: 3, type: !4)