[Debuginfo][Instcombiner] Do not clone dbg.declare.

TryToSinkInstruction() has a bug: While updating debug info for
sunk instruction, it could clone dbg.declare intrinsic.
That is wrong. There could be only one dbg.declare.
The fix is to not clone dbg.declare intrinsic and to update
it`s arguments, to not to point to sunk instruction.

Differential Revision: https://reviews.llvm.org/D67217

llvm-svn: 371587

Author: avl-llvm

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -3164,6 +3164,21 @@ static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
   findDbgUsers(DbgUsers, I);
   for (auto *DII : reverse(DbgUsers)) {
     if (DII->getParent() == SrcBlock) {
+      if (isa<DbgDeclareInst>(DII)) {
+        // A dbg.declare instruction should not be cloned, since there can only be
+        // one per variable fragment. It should be left in the original place since
+        // sunk instruction is not an alloca(otherwise we could not be here).
+        // But we need to update arguments of dbg.declare instruction, so that it
+        // would not point into sunk instruction.
+        if (!isa<CastInst>(I))
+          continue; // dbg.declare points at something it shouldn't
+
+        DII->setOperand(
+            0, MetadataAsValue::get(I->getContext(),
+                                    ValueAsMetadata::get(I->getOperand(0))));
+        continue;
+      }
+
       // dbg.value is in the same basic block as the sunk inst, see if we can
       // salvage it. Clone a new copy of the instruction: on success we need
       // both salvaged and unsalvaged copies.

llvm/test/Transforms/InstCombine/do-not-clone-dbg-declare.ll

@@ -0,0 +1,144 @@
+
+; RUN: opt %s -instcombine -verify -S -o - | FileCheck %s
+
+; Hand-reduced from this example.
+; -g -O -mllvm -disable-llvm-optzns -gno-column-info
+; plus opt -sroa -instcombine -inline
+
+; #include <stdio.h>
+;
+; struct S1 {
+;     int p1;
+;     int p2;
+;
+;     bool IsNull (  ) {
+;         return p1 == 0;
+;     }
+; };
+;
+; S1 foo ( void );
+;
+; int bar (  ) {
+;
+;     S1 result = foo();
+;
+;     if ( result.IsNull() )
+;         return 0;
+;
+;     result.p1 = 2;
+;     result.p2 = 3;
+;
+;     int* ptr = &result.p1;
+;
+;     printf("%d", *ptr);
+;     printf("%d", *(ptr+1));
+;
+;     return result.p1 + 1;
+; }
+
+; CHECK: _Z3barv
+; CHECK: llvm.dbg.declare(metadata i64* %{{.*}}, metadata [[METADATA_IDX1:![0-9]+]]
+; CHECK-NOT: llvm.dbg.declare(metadata %struct.S1* %{{.*}}, metadata [[METADATA_IDX1]]
+; CHECK: ret
+; CHECK: DICompileUnit
+; CHECK: [[METADATA_IDX1]] = !DILocalVariable(name: "result"
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.S1 = type { i32, i32 }
+
+@.str = private unnamed_addr constant [3 x i8] c"%d\00", align 1
+
+define dso_local i32 @_Z3barv() !dbg !7 {
+entry:
+  %result = alloca i64, align 8
+  %tmpcast = bitcast i64* %result to %struct.S1*
+  %0 = bitcast i64* %result to i8*, !dbg !24
+  call void @llvm.lifetime.start.p0i8(i64 8, i8* nonnull %0) #4, !dbg !24
+  call void @llvm.dbg.declare(metadata %struct.S1* %tmpcast, metadata !12, metadata !DIExpression()), !dbg !24
+  %call = call i64 @_Z3foov(), !dbg !24
+  store i64 %call, i64* %result, align 8, !dbg !24
+  call void @llvm.dbg.value(metadata %struct.S1* %tmpcast, metadata !25, metadata !DIExpression()), !dbg !29
+  %p1.i = getelementptr inbounds %struct.S1, %struct.S1* %tmpcast, i64 0, i32 0, !dbg !32
+  %1 = load i32, i32* %p1.i, align 4, !dbg !32
+  %cmp.i = icmp eq i32 %1, 0, !dbg !32
+  br i1 %cmp.i, label %if.then, label %if.end, !dbg !38
+
+if.then:                                          ; preds = %entry
+  br label %cleanup, !dbg !38
+
+if.end:                                           ; preds = %entry
+
+  %p1 = bitcast i64* %result to i32*, !dbg !38
+  store i32 2, i32* %p1, align 8, !dbg !38
+  %p2 = getelementptr inbounds %struct.S1, %struct.S1* %tmpcast, i64 0, i32 1, !dbg !38
+  store i32 3, i32* %p2, align 4, !dbg !38
+  %p12 = bitcast i64* %result to i32*, !dbg !38
+  call void @llvm.dbg.value(metadata i32* %p12, metadata !22, metadata !DIExpression()), !dbg !38
+  %call3 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i32 2), !dbg !38
+  %add.ptr = getelementptr inbounds i32, i32* %p12, i64 1, !dbg !38
+  %2 = load i32, i32* %add.ptr, align 4, !dbg !38
+  %call4 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i32 %2), !dbg !38
+  %p15 = bitcast i64* %result to i32*, !dbg !38
+  %3 = load i32, i32* %p15, align 8, !dbg !38
+  %add = add nsw i32 %3, 1, !dbg !38
+  br label %cleanup
+
+cleanup:                                          ; preds = %if.end, %if.then
+  %retval.0 = phi i32 [ 0, %if.then ], [ %add, %if.end ], !dbg !38
+  %4 = bitcast i64* %result to i8*, !dbg !38
+  call void @llvm.lifetime.end.p0i8(i64 8, i8* nonnull %4) #4, !dbg !38
+  ret i32 %retval.0, !dbg !38
+}
+
+declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #1
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #2
+
+declare dso_local i64 @_Z3foov() #3
+
+declare dso_local i32 @printf(i8*, ...) #3
+
+declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #1
+
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "test.cpp", directory: "")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang"}
+!7 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !1, file: !1, line: 15, type: !8, scopeLine: 15, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !{!12, !22}
+!12 = !DILocalVariable(name: "result", scope: !7, file: !1, line: 17, type: !13)
+!13 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S1", file: !1, line: 4, size: 64, flags: DIFlagTypePassByValue, elements: !14, identifier: "_ZTS2S1")
+!14 = !{!15, !16, !17}
+!15 = !DIDerivedType(tag: DW_TAG_member, name: "p1", scope: !13, file: !1, line: 5, baseType: !10, size: 32)
+!16 = !DIDerivedType(tag: DW_TAG_member, name: "p2", scope: !13, file: !1, line: 6, baseType: !10, size: 32, offset: 32)
+!17 = !DISubprogram(name: "IsNull", linkageName: "_ZN2S16IsNullEv", scope: !13, file: !1, line: 8, type: !18, scopeLine: 8, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized)
+!18 = !DISubroutineType(types: !19)
+!19 = !{!20, !21}
+!20 = !DIBasicType(name: "bool", size: 8, encoding: DW_ATE_boolean)
+!21 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
+!22 = !DILocalVariable(name: "ptr", scope: !7, file: !1, line: 25, type: !23)
+!23 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64)
+!24 = !DILocation(line: 17, scope: !7)
+!25 = !DILocalVariable(name: "this", arg: 1, scope: !26, type: !28, flags: DIFlagArtificial | DIFlagObjectPointer)
+!26 = distinct !DISubprogram(name: "IsNull", linkageName: "_ZN2S16IsNullEv", scope: !13, file: !1, line: 8, type: !18, scopeLine: 8, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, declaration: !17, retainedNodes: !27)
+!27 = !{!25}
+!28 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 64)
+!29 = !DILocation(line: 0, scope: !26, inlinedAt: !30)
+!30 = distinct !DILocation(line: 19, scope: !31)
+!31 = distinct !DILexicalBlock(scope: !7, file: !1, line: 19)
+!32 = !DILocation(line: 9, scope: !26, inlinedAt: !30)
+!38 = !DILocation(line: 0, scope: !7)