forked from OSchip/llvm-project
[GVNHoist] Merge DebugLoc metadata on hoisted instructions
Summary:
When instructions are hoisted, current implementation keeps DebugLoc metadata of the instruction that chosen as Repl (and its GEP operand if Repl is a load or a store). However, DebugLoc metadata should be updated to the 'merged' location across all hoisted instructions. See the following example code:
```
1: typedef struct {
2: int a[10];
3: } S1;
4:
5: extern S1 *s1[10];
6:
7: void foo(int x, int y, int i) {
8: if (y)
9: s1[i]->a[i] = x + y;
10: else
11: s1[i]->a[i] = x;
12: }
```
Below is LLVM IR representation of the program before gvn-hoist:
```
%struct.S1 = type { [10 x i32] }
@s1 = external local_unnamed_addr global [10 x %struct.S1*], align 16
define void @foo(i32 %x, i32 %y, i32 %i) !dbg !4 {
entry:
%tobool = icmp ne i32 %y, 0, !dbg !8
br i1 %tobool, label %if.then, label %if.else, !dbg !10
if.then: ; preds = %entry
%add = add nsw i32 %x, %y, !dbg !11
%idxprom = sext i32 %i to i64, !dbg !12
%arrayidx = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom, !dbg !12
%0 = load %struct.S1*, %struct.S1** %arrayidx, align 8, !dbg !12, !tbaa !13
%a = getelementptr inbounds %struct.S1, %struct.S1* %0, i32 0, i32 0, !dbg !17
br label %if.end, !dbg !12
if.else: ; preds = %entry
%idxprom3 = sext i32 %i to i64, !dbg !18
%arrayidx4 = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom3, !dbg !18
%1 = load %struct.S1*, %struct.S1** %arrayidx4, align 8, !dbg !18, !tbaa !13
%a5 = getelementptr inbounds %struct.S1, %struct.S1* %1, i32 0, i32 0, !dbg !19
br label %if.end
if.end: ; preds = %if.else, %if.then
%a5.sink = phi [10 x i32]* [ %a5, %if.else ], [ %a, %if.then ]
%.sink = phi i32 [ %x, %if.else ], [ %add, %if.then ]
%idxprom6 = sext i32 %i to i64
%arrayidx7 = getelementptr inbounds [10 x i32], [10 x i32]* %a5.sink, i64 0, i64 %idxprom6
store i32 %.sink, i32* %arrayidx7, align 4, !tbaa !20
ret void, !dbg !22
}
```
where
```
!11 = !DILocation(line: 9, column: 18, scope: !9)
!12 = !DILocation(line: 9, column: 5, scope: !9)
!18 = !DILocation(line: 11, column: 5, scope: !9)
!19 = !DILocation(line: 11, column: 9, scope: !9)
```
. And below is after gvn-hoist:
```
define void @foo(i32 %x, i32 %y, i32 %i) !dbg !4 {
entry:
%tobool = icmp ne i32 %y, 0, !dbg !8
%idxprom = sext i32 %i to i64, !dbg !10
%0 = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom, !dbg !10
%1 = load %struct.S1*, %struct.S1** %0, align 8, !dbg !10, !tbaa !11
br i1 %tobool, label %if.then, label %if.else, !dbg !15
if.then: ; preds = %entry
%add = add nsw i32 %x, %y, !dbg !16
%arrayidx = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom, !dbg !10
%a = getelementptr inbounds %struct.S1, %struct.S1* %1, i32 0, i32 0, !dbg !17
br label %if.end, !dbg !10
if.else: ; preds = %entry
%arrayidx4 = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom, !dbg !18
%a5 = getelementptr inbounds %struct.S1, %struct.S1* %1, i32 0, i32 0, !dbg !19
br label %if.end
if.end: ; preds = %if.else, %if.then
%a5.sink = phi [10 x i32]* [ %a5, %if.else ], [ %a, %if.then ]
%.sink = phi i32 [ %x, %if.else ], [ %add, %if.then ]
%arrayidx7 = getelementptr inbounds [10 x i32], [10 x i32]* %a5.sink, i64 0, i64 %idxprom
store i32 %.sink, i32* %arrayidx7, align 4, !tbaa !20
ret void, !dbg !22
}
```
As you see, loads and their GEPs have been hosited from if.then/if.else block to entry block. However, DebugLoc metadata of these new instructions are still same as the instructions in if.then block, as they are moved/cloned from if.then block. This may result incorrect stepping and imprecise sample profile result.
Reviewers: majnemer, pcc, sebpop
Reviewed By: sebpop
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29377
llvm-svn: 294250
This commit is contained in:
Taewook Oh
parent
6f2db57dae
commit
44a856f7d5
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@ -24,6 +24,7 @@
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/DebugInfoMetadata.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Transforms/Utils/MemorySSA.h"
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@ -714,6 +715,9 @@ private:
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OtherGep = cast<GetElementPtrInst>(
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cast<StoreInst>(OtherInst)->getPointerOperand());
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ClonedGep->andIRFlags(OtherGep);
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ClonedGep->setDebugLoc(
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DILocation::getMergedLocation(
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ClonedGep->getDebugLoc(), OtherGep->getDebugLoc()));
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}
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// Replace uses of Gep with ClonedGep in Repl.
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@ -862,6 +866,9 @@ private:
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}
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Repl->andIRFlags(I);
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Repl->setDebugLoc(
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DILocation::getMergedLocation(
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Repl->getDebugLoc(), I->getDebugLoc()));
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combineKnownMetadata(Repl, I);
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I->replaceAllUsesWith(Repl);
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// Also invalidate the Alias Analysis cache.
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@ -0,0 +1,69 @@
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; RUN: opt < %s -gvn-hoist -S | FileCheck %s
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; CHECK: [[VREG:%[^ ]+]] = getelementptr{{.*}}@s1
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; CHECK-NOT: !dbg
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; CHECK-SAME: {{$}}
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; CHECK-NEXT: load{{.*}}[[VREG]]
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; CHECK-NOT: !dbg
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; CHECK-SAME: {{$}}
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target triple = "x86_64-unknown-linux-gnu"
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%struct.S1 = type { [10 x i32] }
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@s1 = external local_unnamed_addr global [10 x %struct.S1*], align 16
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define void @foo(i32 %x, i32 %y, i32 %i) !dbg !4 {
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entry:
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%tobool = icmp ne i32 %y, 0, !dbg !8
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br i1 %tobool, label %if.then, label %if.else, !dbg !10
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if.then: ; preds = %entry
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%add = add nsw i32 %x, %y, !dbg !11
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%idxprom = sext i32 %i to i64, !dbg !12
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%arrayidx = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom, !dbg !12
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%0 = load %struct.S1*, %struct.S1** %arrayidx, align 8, !dbg !12, !tbaa !13
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%a = getelementptr inbounds %struct.S1, %struct.S1* %0, i32 0, i32 0, !dbg !17
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br label %if.end, !dbg !12
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if.else: ; preds = %entry
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%idxprom3 = sext i32 %i to i64, !dbg !18
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%arrayidx4 = getelementptr inbounds [10 x %struct.S1*], [10 x %struct.S1*]* @s1, i64 0, i64 %idxprom3, !dbg !18
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%1 = load %struct.S1*, %struct.S1** %arrayidx4, align 8, !dbg !18, !tbaa !13
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%a5 = getelementptr inbounds %struct.S1, %struct.S1* %1, i32 0, i32 0, !dbg !19
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br label %if.end
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if.end: ; preds = %if.else, %if.then
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%a5.sink = phi [10 x i32]* [ %a5, %if.else ], [ %a, %if.then ]
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%.sink = phi i32 [ %x, %if.else ], [ %add, %if.then ]
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%idxprom6 = sext i32 %i to i64
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%arrayidx7 = getelementptr inbounds [10 x i32], [10 x i32]* %a5.sink, i64 0, i64 %idxprom6
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store i32 %.sink, i32* %arrayidx7, align 4, !tbaa !20
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ret void, !dbg !22
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}
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!2, !3}
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!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1)
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!1 = !DIFile(filename: "foo.c", directory: "b/")
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!2 = !{i32 2, !"Dwarf Version", i32 4}
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!3 = !{i32 2, !"Debug Info Version", i32 3}
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!4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 7, type: !5, isLocal: false, isDefinition: true, scopeLine: 7, flags: DIFlagPrototyped, isOptimized: true, unit: !0)
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!5 = !DISubroutineType(types: !6)
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!6 = !{null, !7, !7, !7}
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!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!8 = !DILocation(line: 8, column: 7, scope: !9)
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!9 = distinct !DILexicalBlock(scope: !4, file: !1, line: 8, column: 7)
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!10 = !DILocation(line: 8, column: 7, scope: !4)
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!11 = !DILocation(line: 9, column: 18, scope: !9)
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!12 = !DILocation(line: 9, column: 5, scope: !9)
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!13 = !{!14, !14, i64 0}
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!14 = !{!"any pointer", !15, i64 0}
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!15 = !{!"omnipotent char", !16, i64 0}
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!16 = !{!"Simple C/C++ TBAA"}
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!17 = !DILocation(line: 9, column: 9, scope: !9)
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!18 = !DILocation(line: 11, column: 5, scope: !9)
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!19 = !DILocation(line: 11, column: 9, scope: !9)
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!20 = !{!21, !21, i64 0}
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!21 = !{!"int", !15, i64 0}
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!22 = !DILocation(line: 12, column: 1, scope: !4)
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