[DebugInfo] Insert DW_OP_deref when spilling indirect DBG_VALUEs

Summary:
This comes up in optimized debug info for C++ programs that pass and
return objects indirectly by address. In these programs,
llvm.dbg.declare survives optimization, which causes us to emit indirect
DBG_VALUE instructions. The fast register allocator knows to insert
DW_OP_deref when spilling indirect DBG_VALUE instructions, but the
LiveDebugVariables did not until this change.

This fixes part of PR34513. I need to look into why this doesn't work at
-O0 and I'll send follow up patches to handle that.

Reviewers: aprantl, dblaikie, probinson

Subscribers: qcolombet, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D37911

llvm-svn: 313400

3 files changed, 195 insertions, 3 deletions

diff --git a/llvm/test/DebugInfo/X86/bbjoin.ll b/llvm/test/DebugInfo/X86/bbjoin.ll
index 4cb99410dd6..a41bde6d40b 100644
--- a/llvm/test/DebugInfo/X86/bbjoin.ll
+++ b/llvm/test/DebugInfo/X86/bbjoin.ll
@@ -11,12 +11,12 @@
 ; }
 ; CHECK: ![[X:.*]] = !DILocalVariable(name: "x",
 ; CHECK: bb.0.entry:
-; CHECK:   DBG_VALUE 23, 0, ![[X]],
+; CHECK:   DBG_VALUE 23, debug-use _, ![[X]],
 ; CHECK:   DBG_VALUE %rsp, 0, ![[X]], !DIExpression(DW_OP_plus_uconst, 4, DW_OP_deref),
 ; CHECK: bb.1.if.then:
-; CHECK:   DBG_VALUE 43, 0, ![[X]],
+; CHECK:   DBG_VALUE 43, debug-use _, ![[X]],
 ; CHECK: bb.2.if.end:
-; CHECK-NOT:  DBG_VALUE 23, 0, ![[X]],
+; CHECK-NOT:  DBG_VALUE 23, debug-use _, ![[X]],
 ; CHECK:   RETQ %eax
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
diff --git a/llvm/test/DebugInfo/X86/spill-indirect-nrvo.ll b/llvm/test/DebugInfo/X86/spill-indirect-nrvo.ll
new file mode 100644
index 00000000000..ec2959701e4
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/spill-indirect-nrvo.ll
@@ -0,0 +1,103 @@
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -O0 < %s | FileCheck %s
+
+; Make sure we insert DW_OP_deref when spilling indirect DBG_VALUE instructions.
+
+; C++ source:
+; #define FORCE_SPILL() \
+;   __asm volatile("" : : : \
+;                    "rax", "rbx", "rcx", "rdx", "rsi", "rdi", "rbp", "r8", \
+;                    "r9", "r10", "r11", "r12", "r13", "r14", "r15")
+; struct string {
+;   string();
+;   string(int i);
+;   ~string();
+;   int i = 0;
+; };
+; string get_string() {
+;   string result = 3;
+;   FORCE_SPILL();
+;   return result;
+; }
+
+; CHECK-LABEL: _Z10get_stringv:
+; CHECK: #DEBUG_VALUE: get_string:result <- [%RDI+0]
+; CHECK: movq   %rdi, [[OFFS:[0-9]+]](%rsp)          # 8-byte Spill
+; CHECK: #DEBUG_VALUE: get_string:result <- [DW_OP_plus_uconst [[OFFS]], DW_OP_deref] [%RSP+0]
+; CHECK: callq  _ZN6stringC1Ei
+; CHECK: #APP
+; CHECK: #NO_APP
+
+; ModuleID = 't.cpp'
+source_filename = "t.cpp"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+%struct.string = type { i32 }
+
+; Function Attrs: uwtable
+define void @_Z10get_stringv(%struct.string* noalias sret %agg.result) #0 !dbg !7 {
+entry:
+  %nrvo = alloca i1, align 1
+  store i1 false, i1* %nrvo, align 1, !dbg !24
+  call void @llvm.dbg.declare(metadata %struct.string* %agg.result, metadata !23, metadata !DIExpression()), !dbg !25
+  call void @_ZN6stringC1Ei(%struct.string* %agg.result, i32 3), !dbg !26
+  call void asm sideeffect "", "~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15},~{dirflag},~{fpsr},~{flags}"() #3, !dbg !27, !srcloc !28
+  store i1 true, i1* %nrvo, align 1, !dbg !29
+  %nrvo.val = load i1, i1* %nrvo, align 1, !dbg !30
+  br i1 %nrvo.val, label %nrvo.skipdtor, label %nrvo.unused, !dbg !30
+
+nrvo.unused:                                      ; preds = %entry
+  call void @_ZN6stringD1Ev(%struct.string* %agg.result), !dbg !30
+  br label %nrvo.skipdtor, !dbg !30
+
+nrvo.skipdtor:                                    ; preds = %nrvo.unused, %entry
+  ret void, !dbg !30
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+declare void @_ZN6stringC1Ei(%struct.string*, i32) unnamed_addr
+
+declare void @_ZN6stringD1Ev(%struct.string*) unnamed_addr
+
+attributes #0 = { uwtable }
+attributes #1 = { nounwind readnone speculatable }
+attributes #3 = { nounwind }
+
+!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 version 6.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "t.cpp", directory: "C:\5Csrc\5Cllvm-project\5Cbuild")
+!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 version 6.0.0 "}
+!7 = distinct !DISubprogram(name: "get_string", linkageName: "_Z10get_stringv", scope: !1, file: !1, line: 13, type: !8, isLocal: false, isDefinition: true, scopeLine: 13, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !22)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10}
+!10 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "string", file: !1, line: 7, size: 32, elements: !11, identifier: "_ZTS6string")
+!11 = !{!12, !14, !18, !21}
+!12 = !DIDerivedType(tag: DW_TAG_member, name: "i", scope: !10, file: !1, line: 11, baseType: !13, size: 32)
+!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!14 = !DISubprogram(name: "string", scope: !10, file: !1, line: 8, type: !15, isLocal: false, isDefinition: false, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: true)
+!15 = !DISubroutineType(types: !16)
+!16 = !{null, !17}
+!17 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
+!18 = !DISubprogram(name: "string", scope: !10, file: !1, line: 9, type: !19, isLocal: false, isDefinition: false, scopeLine: 9, flags: DIFlagPrototyped, isOptimized: true)
+!19 = !DISubroutineType(types: !20)
+!20 = !{null, !17, !13}
+!21 = !DISubprogram(name: "~string", scope: !10, file: !1, line: 10, type: !15, isLocal: false, isDefinition: false, scopeLine: 10, flags: DIFlagPrototyped, isOptimized: true)
+!22 = !{!23}
+!23 = !DILocalVariable(name: "result", scope: !7, file: !1, line: 14, type: !10)
+!24 = !DILocation(line: 14, column: 3, scope: !7)
+!25 = !DILocation(line: 14, column: 10, scope: !7)
+!26 = !DILocation(line: 14, column: 19, scope: !7)
+!27 = !DILocation(line: 15, column: 3, scope: !7)
+!28 = !{i32 -2147471175}
+!29 = !DILocation(line: 16, column: 3, scope: !7)
+!30 = !DILocation(line: 17, column: 1, scope: !7)
diff --git a/llvm/test/DebugInfo/X86/spill-nontrivial-param.ll b/llvm/test/DebugInfo/X86/spill-nontrivial-param.ll
new file mode 100644
index 00000000000..9ac82374a0e
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/spill-nontrivial-param.ll
@@ -0,0 +1,89 @@
+; RUN: llc < %s | FileCheck %s
+
+; Make sure we insert DW_OP_deref when spilling indirect DBG_VALUE instructions.
+; In this example, 'nt' is passed by address because it is not trivially
+; copyable. When we spill the physical argument register at the barrier, we need
+; to insert DW_OP_deref.
+
+; #define FORCE_SPILL() \
+;   __asm volatile("" : : : \
+;                    "rax", "rbx", "rcx", "rdx", "rsi", "rdi", "rbp", "r8", \
+;                    "r9", "r10", "r11", "r12", "r13", "r14", "r15")
+; struct NonTrivial {
+;   NonTrivial();
+;   ~NonTrivial();
+;   int i;
+; };
+; int foo(NonTrivial nt) {
+;   FORCE_SPILL();
+;   return nt.i;
+; }
+
+; CHECK-LABEL: _Z3foo10NonTrivial:
+; CHECK: #DEBUG_VALUE: foo:nt <- [%RDI+0]
+; CHECK: movq    %rdi, -8(%rsp)          # 8-byte Spill
+; CHECK: #DEBUG_VALUE: foo:nt <- [DW_OP_constu 8, DW_OP_minus, DW_OP_deref] [%RSP+0]
+; CHECK: #APP
+; CHECK: #NO_APP
+; CHECK: movq    -8(%rsp), %rax          # 8-byte Reload
+; CHECK: movl    (%rax), %eax
+
+; ModuleID = 't.cpp'
+source_filename = "t.cpp"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+%struct.NonTrivial = type { i32 }
+
+; Function Attrs: nounwind uwtable
+define i32 @_Z3foo10NonTrivial(%struct.NonTrivial* nocapture readonly %nt) local_unnamed_addr #0 !dbg !7 {
+entry:
+  tail call void @llvm.dbg.declare(metadata %struct.NonTrivial* %nt, metadata !20, metadata !DIExpression()), !dbg !21
+  tail call void asm sideeffect "", "~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15},~{dirflag},~{fpsr},~{flags}"() #2, !dbg !22, !srcloc !23
+  %i = getelementptr inbounds %struct.NonTrivial, %struct.NonTrivial* %nt, i64 0, i32 0, !dbg !24
+  %0 = load i32, i32* %i, align 4, !dbg !24, !tbaa !25
+  ret i32 %0, !dbg !30
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+attributes #0 = { nounwind uwtable }
+attributes #1 = { nounwind readnone speculatable }
+attributes #2 = { nounwind }
+
+!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 version 6.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "t.cpp", directory: "C:\5Csrc\5Cllvm-project\5Cbuild")
+!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 version 6.0.0 "}
+!7 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foo10NonTrivial", scope: !1, file: !1, line: 10, type: !8, isLocal: false, isDefinition: true, scopeLine: 10, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !19)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !11}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "NonTrivial", file: !1, line: 5, size: 32, elements: !12, identifier: "_ZTS10NonTrivial")
+!12 = !{!13, !14, !18}
+!13 = !DIDerivedType(tag: DW_TAG_member, name: "i", scope: !11, file: !1, line: 8, baseType: !10, size: 32)
+!14 = !DISubprogram(name: "NonTrivial", scope: !11, file: !1, line: 6, type: !15, isLocal: false, isDefinition: false, scopeLine: 6, flags: DIFlagPrototyped, isOptimized: true)
+!15 = !DISubroutineType(types: !16)
+!16 = !{null, !17}
+!17 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !11, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
+!18 = !DISubprogram(name: "~NonTrivial", scope: !11, file: !1, line: 7, type: !15, isLocal: false, isDefinition: false, scopeLine: 7, flags: DIFlagPrototyped, isOptimized: true)
+!19 = !{!20}
+!20 = !DILocalVariable(name: "nt", arg: 1, scope: !7, file: !1, line: 10, type: !11)
+!21 = !DILocation(line: 10, column: 20, scope: !7)
+!22 = !DILocation(line: 11, column: 3, scope: !7)
+!23 = !{i32 -2147471481}
+!24 = !DILocation(line: 12, column: 13, scope: !7)
+!25 = !{!26, !27, i64 0}
+!26 = !{!"_ZTS10NonTrivial", !27, i64 0}
+!27 = !{!"int", !28, i64 0}
+!28 = !{!"omnipotent char", !29, i64 0}
+!29 = !{!"Simple C++ TBAA"}
+!30 = !DILocation(line: 12, column: 3, scope: !7)