From 849f3bf8c9f40f36bb1b3892b159a1d1eed0e079 Mon Sep 17 00:00:00 2001 From: "Arnaud A. de Grandmaison" Date: Thu, 1 Oct 2015 14:54:31 +0000 Subject: [PATCH] [InstCombine] Remove trivially empty lifetime start/end ranges. Summary: Some passes may open up opportunities for optimizations, leaving empty lifetime start/end ranges. For example, with the following code: void foo(char *, char *); void bar(int Size, bool flag) { for (int i = 0; i < Size; ++i) { char text[1]; char buff[1]; if (flag) foo(text, buff); // BBFoo } } the loop unswitch pass will create 2 versions of the loop, one with flag==true, and the other one with flag==false, but always leaving the BBFoo basic block, with lifetime ranges covering the scope of the for loop. Simplify CFG will then remove BBFoo in the case where flag==false, but will leave the lifetime markers. This patch teaches InstCombine to remove trivially empty lifetime marker ranges, that is ranges ending right after they were started (ignoring debug info or other lifetime markers in the range). This fixes PR24598: excessive compile time after r234581. Reviewers: reames, chandlerc Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D13305 llvm-svn: 249018 --- .../InstCombine/InstCombineCalls.cpp | 23 +++++ llvm/test/Transforms/InstCombine/lifetime.ll | 93 +++++++++++++++++++ 2 files changed, 116 insertions(+) create mode 100644 llvm/test/Transforms/InstCombine/lifetime.ll diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp index 8f3deacf248d..b1a20ff3e6e2 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp @@ -1433,6 +1433,29 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) { return EraseInstFromFunction(CI); break; } + case Intrinsic::lifetime_start: { + // Remove trivially empty lifetime_start/end ranges, i.e. a start + // immediately followed by an end (ignoring debuginfo or other + // lifetime markers in between). + BasicBlock::iterator BI = II, BE = II->getParent()->end(); + for (++BI; BI != BE; ++BI) { + if (IntrinsicInst *LTE = dyn_cast(BI)) { + if (isa(LTE) || + LTE->getIntrinsicID() == Intrinsic::lifetime_start) + continue; + if (LTE->getIntrinsicID() == Intrinsic::lifetime_end) { + if (II->getOperand(0) == LTE->getOperand(0) && + II->getOperand(1) == LTE->getOperand(1)) { + EraseInstFromFunction(*LTE); + return EraseInstFromFunction(*II); + } + continue; + } + } + break; + } + break; + } case Intrinsic::assume: { // Canonicalize assume(a && b) -> assume(a); assume(b); // Note: New assumption intrinsics created here are registered by diff --git a/llvm/test/Transforms/InstCombine/lifetime.ll b/llvm/test/Transforms/InstCombine/lifetime.ll new file mode 100644 index 000000000000..57b19fb0a823 --- /dev/null +++ b/llvm/test/Transforms/InstCombine/lifetime.ll @@ -0,0 +1,93 @@ +; RUN: opt < %s -instcombine -S | FileCheck %s + +declare void @llvm.dbg.declare(metadata, metadata, metadata) +declare void @llvm.lifetime.start(i64, i8* nocapture) +declare void @llvm.lifetime.end(i64, i8* nocapture) +declare void @foo(i8* nocapture, i8* nocapture) + +define void @bar(i1 %flag) { +entry: +; CHECK-LABEL: @bar( +; CHECK: %[[T:[^ ]+]] = getelementptr inbounds [1 x i8], [1 x i8]* %text +; CHECK: %[[B:[^ ]+]] = getelementptr inbounds [1 x i8], [1 x i8]* %buff +; CHECK: if: +; CHECK-NEXT: br label %bb2 +; CHECK: bb2: +; CHECK-NEXT: br label %bb3 +; CHECK: bb3: +; CHECK-NEXT: call void @llvm.dbg.declare +; CHECK-NEXT: br label %fin +; CHECK: call void @llvm.lifetime.start(i64 1, i8* %[[T]]) +; CHECK-NEXT: call void @llvm.lifetime.start(i64 1, i8* %[[B]]) +; CHECK-NEXT: call void @foo(i8* %[[B]], i8* %[[T]]) +; CHECK-NEXT: call void @llvm.lifetime.end(i64 1, i8* %[[B]]) +; CHECK-NEXT: call void @llvm.lifetime.end(i64 1, i8* %[[T]]) + %text = alloca [1 x i8], align 1 + %buff = alloca [1 x i8], align 1 + %0 = getelementptr inbounds [1 x i8], [1 x i8]* %text, i64 0, i64 0 + %1 = getelementptr inbounds [1 x i8], [1 x i8]* %buff, i64 0, i64 0 + br i1 %flag, label %if, label %else + +if: + call void @llvm.lifetime.start(i64 1, i8* %0) + call void @llvm.lifetime.start(i64 1, i8* %1) + call void @llvm.lifetime.end(i64 1, i8* %1) + call void @llvm.lifetime.end(i64 1, i8* %0) + br label %bb2 + +bb2: + call void @llvm.lifetime.start(i64 1, i8* %0) + call void @llvm.lifetime.start(i64 1, i8* %1) + call void @llvm.lifetime.end(i64 1, i8* %0) + call void @llvm.lifetime.end(i64 1, i8* %1) + br label %bb3 + +bb3: + call void @llvm.lifetime.start(i64 1, i8* %0) + call void @llvm.dbg.declare(metadata [1 x i8]* %text, metadata !14, metadata !25), !dbg !26 + call void @llvm.lifetime.end(i64 1, i8* %0) + br label %fin + +else: + call void @llvm.lifetime.start(i64 1, i8* %0) + call void @llvm.lifetime.start(i64 1, i8* %1) + call void @foo(i8* %1, i8* %0) + call void @llvm.lifetime.end(i64 1, i8* %1) + call void @llvm.lifetime.end(i64 1, i8* %0) + br label %fin + +fin: + ret void +} + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!22, !23} +!llvm.ident = !{!24} + +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.8.0 (trunk 248826) (llvm/trunk 248827)", isOptimized: true, runtimeVersion: 0, emissionKind: 1, enums: !2, subprograms: !3) +!1 = !DIFile(filename: "test.cpp", directory: "/home/user") +!2 = !{} +!3 = !{!4} +!4 = distinct !DISubprogram(name: "bar", linkageName: "bar", scope: !1, file: !1, line: 2, type: !5, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true, function: void (i1)* @bar, variables: !8) +!5 = !DISubroutineType(types: !6) +!6 = !{null, !7} +!7 = !DIBasicType(name: "bool", size: 8, align: 8, encoding: DW_ATE_boolean) +!8 = !{!9, !11, !12, !14, !21} +!9 = !DILocalVariable(name: "Size", arg: 1, scope: !4, file: !1, line: 2, type: !10) +!10 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed) +!11 = !DILocalVariable(name: "flag", arg: 2, scope: !4, file: !1, line: 2, type: !7) +!12 = !DILocalVariable(name: "i", scope: !13, file: !1, line: 3, type: !10) +!13 = distinct !DILexicalBlock(scope: !4, file: !1, line: 3, column: 3) +!14 = !DILocalVariable(name: "text", scope: !15, file: !1, line: 4, type: !17) +!15 = distinct !DILexicalBlock(scope: !16, file: !1, line: 3, column: 30) +!16 = distinct !DILexicalBlock(scope: !13, file: !1, line: 3, column: 3) +!17 = !DICompositeType(tag: DW_TAG_array_type, baseType: !18, size: 8, align: 8, elements: !19) +!18 = !DIBasicType(name: "char", size: 8, align: 8, encoding: DW_ATE_signed_char) +!19 = !{!20} +!20 = !DISubrange(count: 1) +!21 = !DILocalVariable(name: "buff", scope: !15, file: !1, line: 5, type: !17) +!22 = !{i32 2, !"Dwarf Version", i32 4} +!23 = !{i32 2, !"Debug Info Version", i32 3} +!24 = !{!"clang version 3.8.0 (trunk 248826) (llvm/trunk 248827)"} +!25 = !DIExpression() +!26 = !DILocation(line: 4, column: 10, scope: !15)