[llvm] r249018 - [InstCombine] Remove trivially empty lifetime start/end ranges.
Arnaud A. de Grandmaison via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 1 07:54:31 PDT 2015
Author: aadg
Date: Thu Oct 1 09:54:31 2015
New Revision: 249018
URL: http://llvm.org/viewvc/llvm-project?rev=249018&view=rev
Log:
[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
Added:
llvm/trunk/test/Transforms/InstCombine/lifetime.ll
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=249018&r1=249017&r2=249018&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Thu Oct 1 09:54:31 2015
@@ -1433,6 +1433,29 @@ Instruction *InstCombiner::visitCallInst
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<IntrinsicInst>(BI)) {
+ if (isa<DbgInfoIntrinsic>(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
Added: llvm/trunk/test/Transforms/InstCombine/lifetime.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/lifetime.ll?rev=249018&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/lifetime.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/lifetime.ll Thu Oct 1 09:54:31 2015
@@ -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)
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