MergeFunctions: Preserve debug info in thunks, under option -mergefunc-preserve-debug-info
Summary:
Under option -mergefunc-preserve-debug-info we:
- Do not create a new function for a thunk.
- Retain the debug info for a thunk's parameters (and associated
instructions for the debug info) from the entry block.
Note: -debug will display the algorithm at work.
- Create debug-info for the call (to the shared implementation) made by
a thunk and its return value.
- Erase the rest of the function, retaining the (minimally sized) entry
block to create a thunk.
- Preserve a thunk's call site to point to the thunk even when both occur
within the same translation unit, to aid debugability. Note that this
behaviour differs from the underlying -mergefunc implementation which
modifies the thunk's call site to point to the shared implementation
when both occur within the same translation unit.
Reviewers: echristo, eeckstein, dblaikie, aprantl, friss
Reviewed By: aprantl
Subscribers: davide, fhahn, jfb, mehdi_amini, llvm-commits
Differential Revision: https://reviews.llvm.org/D28075
llvm-svn: 292702
diff --git a/llvm/test/Transforms/MergeFunc/mergefunc-preserve-debug-info.ll b/llvm/test/Transforms/MergeFunc/mergefunc-preserve-debug-info.ll
new file mode 100644
index 0000000..cf76893
--- /dev/null
+++ b/llvm/test/Transforms/MergeFunc/mergefunc-preserve-debug-info.ll
@@ -0,0 +1,223 @@
+; RUN: opt -O0 -S -mergefunc -mergefunc-preserve-debug-info < %s | FileCheck %s --check-prefix=OPTIMIZATION_LEVEL_0
+; RUN: opt -O2 -S -mergefunc -mergefunc-preserve-debug-info < %s | FileCheck %s --check-prefix=OPTIMIZATION_LEVEL_2
+
+; Preserve debug info in thunks under -mergefunc -mergefunc-preserve-debug-info
+;
+; We test that:
+; At -O0 we have preserved the generated @llvm.dbg.declare debug intrinsics.
+; At -O2 we have preserved the generated @llvm.dbg.value debug intrinsics.
+; At -O0, stores from the incoming parameters to locations on the stack-frame
+; and allocas that create these locations on the stack-frame are preserved.
+; Debug info got generated for the call made by the thunk and for its return value.
+; The foregoing is the only content of a thunk's entry block.
+; A thunk makes a tail call to the shared implementation.
+; A thunk's call site is preserved to point to the thunk (with only -mergefunc the
+; call site is modified to point to the shared implementation) when both occur
+; within the same translation unit.
+
+; The source code that was used to test and generate this LLVM IR is:
+;
+; int maxA(int x, int y) {
+; int i, m, j;
+; if (x > y)
+; m = x;
+; else
+; m = y;
+; return m;
+; }
+;
+; int maxB(int x, int y) {
+; int i, m, j;
+; if (x > y)
+; m = x;
+; else
+; m = y;
+; return m;
+; }
+;
+; void f(void) {
+;
+; maxA(3, 4);
+; maxB(1, 9);
+; }
+
+; Function Attrs: nounwind uwtable
+define i32 @maxA(i32 %x, i32 %y) !dbg !6 {
+entry:
+ %x.addr = alloca i32, align 4
+ %y.addr = alloca i32, align 4
+ %i = alloca i32, align 4
+ %m = alloca i32, align 4
+ %j = alloca i32, align 4
+ store i32 %x, i32* %x.addr, align 4
+ call void @llvm.dbg.declare(metadata i32* %x.addr, metadata !11, metadata !12), !dbg !13
+ store i32 %y, i32* %y.addr, align 4
+ call void @llvm.dbg.declare(metadata i32* %y.addr, metadata !14, metadata !12), !dbg !15
+ call void @llvm.dbg.declare(metadata i32* %i, metadata !16, metadata !12), !dbg !17
+ call void @llvm.dbg.declare(metadata i32* %m, metadata !18, metadata !12), !dbg !19
+ call void @llvm.dbg.declare(metadata i32* %j, metadata !20, metadata !12), !dbg !21
+ %0 = load i32, i32* %x.addr, align 4, !dbg !22
+ %1 = load i32, i32* %y.addr, align 4, !dbg !24
+ %cmp = icmp sgt i32 %0, %1, !dbg !25
+ br i1 %cmp, label %if.then, label %if.else, !dbg !26
+
+if.then: ; preds = %entry
+ %2 = load i32, i32* %x.addr, align 4, !dbg !27
+ store i32 %2, i32* %m, align 4, !dbg !28
+ br label %if.end, !dbg !29
+
+if.else: ; preds = %entry
+ %3 = load i32, i32* %y.addr, align 4, !dbg !30
+ store i32 %3, i32* %m, align 4, !dbg !31
+ br label %if.end
+
+if.end: ; preds = %if.else, %if.then
+ %4 = load i32, i32* %m, align 4, !dbg !32
+ ret i32 %4, !dbg !33
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+; Function Attrs: nounwind uwtable
+define i32 @maxB(i32 %x, i32 %y) !dbg !34 {
+
+; OPTIMIZATION_LEVEL_0: define i32 @maxB(i32 %x, i32 %y)
+; OPTIMIZATION_LEVEL_0-NEXT: entry:
+; OPTIMIZATION_LEVEL_0-NEXT: %x.addr = alloca i32, align 4
+; OPTIMIZATION_LEVEL_0-NEXT: %y.addr = alloca i32, align 4
+; OPTIMIZATION_LEVEL_0-NEXT: store i32 %x, i32* %x.addr, align 4
+; OPTIMIZATION_LEVEL_0-NEXT: call void @llvm.dbg.declare(metadata i32* %x.addr, metadata !{{[0-9]+}}, metadata !{{[0-9]+}}), !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_0-NEXT: store i32 %y, i32* %y.addr, align 4
+; OPTIMIZATION_LEVEL_0-NEXT: call void @llvm.dbg.declare(metadata i32* %y.addr, metadata !{{[0-9]+}}, metadata !{{[0-9]+}}), !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_0-NEXT: %0 = tail call i32 @maxA(i32 %x, i32 %y), !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_0-NEXT: ret i32 %0, !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_0-NEXT: }
+
+; OPTIMIZATION_LEVEL_2: define i32 @maxB(i32 %x, i32 %y)
+; OPTIMIZATION_LEVEL_2-NEXT: entry:
+; OPTIMIZATION_LEVEL_2-NEXT: tail call void @llvm.dbg.value(metadata i32 %x, i64 0, metadata !{{[0-9]+}}, metadata !{{[0-9]+}}), !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_2-NEXT: tail call void @llvm.dbg.value(metadata i32 %y, i64 0, metadata !{{[0-9]+}}, metadata !{{[0-9]+}}), !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_2-NEXT: %0 = tail call i32 @maxA(i32 %x, i32 %y) #{{[0-9]+}}, !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_2-NEXT: ret i32 %0, !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_2-NEXT: }
+
+entry:
+ %x.addr = alloca i32, align 4
+ %y.addr = alloca i32, align 4
+ %i = alloca i32, align 4
+ %m = alloca i32, align 4
+ %j = alloca i32, align 4
+ store i32 %x, i32* %x.addr, align 4
+ call void @llvm.dbg.declare(metadata i32* %x.addr, metadata !35, metadata !12), !dbg !36
+ store i32 %y, i32* %y.addr, align 4
+ call void @llvm.dbg.declare(metadata i32* %y.addr, metadata !37, metadata !12), !dbg !38
+ call void @llvm.dbg.declare(metadata i32* %i, metadata !39, metadata !12), !dbg !40
+ call void @llvm.dbg.declare(metadata i32* %m, metadata !41, metadata !12), !dbg !42
+ call void @llvm.dbg.declare(metadata i32* %j, metadata !43, metadata !12), !dbg !44
+ %0 = load i32, i32* %x.addr, align 4, !dbg !45
+ %1 = load i32, i32* %y.addr, align 4, !dbg !47
+ %cmp = icmp sgt i32 %0, %1, !dbg !48
+ br i1 %cmp, label %if.then, label %if.else, !dbg !49
+
+if.then: ; preds = %entry
+ %2 = load i32, i32* %x.addr, align 4, !dbg !50
+ store i32 %2, i32* %m, align 4, !dbg !51
+ br label %if.end, !dbg !52
+
+if.else: ; preds = %entry
+ %3 = load i32, i32* %y.addr, align 4, !dbg !53
+ store i32 %3, i32* %m, align 4, !dbg !54
+ br label %if.end
+
+if.end: ; preds = %if.else, %if.then
+ %4 = load i32, i32* %m, align 4, !dbg !55
+ ret i32 %4, !dbg !56
+}
+
+; Function Attrs: nounwind uwtable
+define void @f() !dbg !57 {
+entry:
+
+; OPTIMIZATION_LEVEL_0: define void @f()
+; OPTIMIZATION_LEVEL_0-NEXT: entry:
+; OPTIMIZATION_LEVEL_0-NEXT: %call = call i32 @maxA(i32 3, i32 4), !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_0-NEXT: %call1 = call i32 @maxB(i32 1, i32 9), !dbg !{{[0-9]+}}
+; OPTIMIZATION_LEVEL_0-NEXT: ret void, !dbg !{{[0-9]+}}
+
+; OPTIMIZATION_LEVEL_2: define void @f()
+; OPTIMIZATION_LEVEL_2-NEXT: entry:
+; OPTIMIZATION_LEVEL_2-NEXT: ret void, !dbg !{{[0-9]+}}
+
+ %call = call i32 @maxA(i32 3, i32 4), !dbg !60
+ %call1 = call i32 @maxB(i32 1, i32 9), !dbg !61
+ ret void, !dbg !62
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "mergefunc-preserve-debug-info.c", directory: "")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{!""}
+!6 = distinct !DISubprogram(name: "maxA", scope: !7, file: !7, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!7 = !DIFile(filename: "./mergefunc-preserve-debug-info.c", directory: "")
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !10, !10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !DILocalVariable(name: "x", arg: 1, scope: !6, file: !7, line: 1, type: !10)
+!12 = !DIExpression()
+!13 = !DILocation(line: 1, column: 14, scope: !6)
+!14 = !DILocalVariable(name: "y", arg: 2, scope: !6, file: !7, line: 1, type: !10)
+!15 = !DILocation(line: 1, column: 21, scope: !6)
+!16 = !DILocalVariable(name: "i", scope: !6, file: !7, line: 2, type: !10)
+!17 = !DILocation(line: 2, column: 7, scope: !6)
+!18 = !DILocalVariable(name: "m", scope: !6, file: !7, line: 2, type: !10)
+!19 = !DILocation(line: 2, column: 10, scope: !6)
+!20 = !DILocalVariable(name: "j", scope: !6, file: !7, line: 2, type: !10)
+!21 = !DILocation(line: 2, column: 13, scope: !6)
+!22 = !DILocation(line: 3, column: 7, scope: !23)
+!23 = distinct !DILexicalBlock(scope: !6, file: !7, line: 3, column: 7)
+!24 = !DILocation(line: 3, column: 11, scope: !23)
+!25 = !DILocation(line: 3, column: 9, scope: !23)
+!26 = !DILocation(line: 3, column: 7, scope: !6)
+!27 = !DILocation(line: 4, column: 9, scope: !23)
+!28 = !DILocation(line: 4, column: 7, scope: !23)
+!29 = !DILocation(line: 4, column: 5, scope: !23)
+!30 = !DILocation(line: 6, column: 9, scope: !23)
+!31 = !DILocation(line: 6, column: 7, scope: !23)
+!32 = !DILocation(line: 7, column: 10, scope: !6)
+!33 = !DILocation(line: 7, column: 3, scope: !6)
+!34 = distinct !DISubprogram(name: "maxB", scope: !7, file: !7, line: 10, type: !8, isLocal: false, isDefinition: true, scopeLine: 10, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!35 = !DILocalVariable(name: "x", arg: 1, scope: !34, file: !7, line: 10, type: !10)
+!36 = !DILocation(line: 10, column: 14, scope: !34)
+!37 = !DILocalVariable(name: "y", arg: 2, scope: !34, file: !7, line: 10, type: !10)
+!38 = !DILocation(line: 10, column: 21, scope: !34)
+!39 = !DILocalVariable(name: "i", scope: !34, file: !7, line: 11, type: !10)
+!40 = !DILocation(line: 11, column: 7, scope: !34)
+!41 = !DILocalVariable(name: "m", scope: !34, file: !7, line: 11, type: !10)
+!42 = !DILocation(line: 11, column: 10, scope: !34)
+!43 = !DILocalVariable(name: "j", scope: !34, file: !7, line: 11, type: !10)
+!44 = !DILocation(line: 11, column: 13, scope: !34)
+!45 = !DILocation(line: 12, column: 7, scope: !46)
+!46 = distinct !DILexicalBlock(scope: !34, file: !7, line: 12, column: 7)
+!47 = !DILocation(line: 12, column: 11, scope: !46)
+!48 = !DILocation(line: 12, column: 9, scope: !46)
+!49 = !DILocation(line: 12, column: 7, scope: !34)
+!50 = !DILocation(line: 13, column: 9, scope: !46)
+!51 = !DILocation(line: 13, column: 7, scope: !46)
+!52 = !DILocation(line: 13, column: 5, scope: !46)
+!53 = !DILocation(line: 15, column: 9, scope: !46)
+!54 = !DILocation(line: 15, column: 7, scope: !46)
+!55 = !DILocation(line: 16, column: 10, scope: !34)
+!56 = !DILocation(line: 16, column: 3, scope: !34)
+!57 = distinct !DISubprogram(name: "f", scope: !7, file: !7, line: 19, type: !58, isLocal: false, isDefinition: true, scopeLine: 19, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!58 = !DISubroutineType(types: !59)
+!59 = !{null}
+!60 = !DILocation(line: 21, column: 3, scope: !57)
+!61 = !DILocation(line: 22, column: 3, scope: !57)
+!62 = !DILocation(line: 23, column: 1, scope: !57)