Pass to emit DWARF path discriminators.

DWARF discriminators are used to distinguish multiple control flow paths
on the same source location. When this happens, instructions across
basic block boundaries will share the same debug location.

This pass detects this situation and creates a new lexical scope to one
of the two instructions. This lexical scope is a child scope of the
original and contains a new discriminator value. This discriminator is
then picked up from MCObjectStreamer::EmitDwarfLocDirective to be
written on the object file.

This fixes http://llvm.org/bugs/show_bug.cgi?id=18270.

llvm-svn: 202752

3 files changed, 212 insertions, 0 deletions

diff --git a/llvm/test/Transforms/AddDiscriminators/basic.ll b/llvm/test/Transforms/AddDiscriminators/basic.ll
new file mode 100644
index 00000000000..b12cbee6adb
--- /dev/null
+++ b/llvm/test/Transforms/AddDiscriminators/basic.ll
@@ -0,0 +1,59 @@
+; RUN: opt < %s -add-discriminators -S | FileCheck %s
+
+; Basic DWARF discriminator test. All the instructions in block
+; 'if.then' should have a different discriminator value than
+; the conditional branch at the end of block 'entry'.
+;
+; Original code:
+;
+;       void foo(int i) {
+;         int x;
+;         if (i < 10) x = i;
+;       }
+
+define void @foo(i32 %i) #0 {
+entry:
+  %i.addr = alloca i32, align 4
+  %x = alloca i32, align 4
+  store i32 %i, i32* %i.addr, align 4
+  %0 = load i32* %i.addr, align 4, !dbg !10
+  %cmp = icmp slt i32 %0, 10, !dbg !10
+  br i1 %cmp, label %if.then, label %if.end, !dbg !10
+
+if.then:                                          ; preds = %entry
+  %1 = load i32* %i.addr, align 4, !dbg !10
+; CHECK:  %1 = load i32* %i.addr, align 4, !dbg !12
+
+  store i32 %1, i32* %x, align 4, !dbg !10
+; CHECK:  store i32 %1, i32* %x, align 4, !dbg !12
+
+  br label %if.end, !dbg !10
+; CHECK:   br label %if.end, !dbg !12
+
+if.end:                                           ; preds = %if.then, %entry
+  ret void, !dbg !12
+}
+
+attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+!llvm.ident = !{!9}
+
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.5 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [basic.c] [DW_LANG_C99]
+!1 = metadata !{metadata !"basic.c", metadata !"."}
+!2 = metadata !{}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"foo", metadata !"foo", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void (i32)* @foo, null, null, metadata !2, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [foo]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [basic.c]
+!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !2, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
+!8 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!9 = metadata !{metadata !"clang version 3.5 "}
+!10 = metadata !{i32 3, i32 0, metadata !11, null}
+!11 = metadata !{i32 786443, metadata !1, metadata !4, i32 3, i32 0, i32 0, i32 0} ; [ DW_TAG_lexical_block ] [basic.c]
+!12 = metadata !{i32 4, i32 0, metadata !4, null}
+
+; CHECK: !12 = metadata !{i32 3, i32 0, metadata !13, null}
+; CHECK: !13 = metadata !{i32 786443, metadata !1, metadata !11, i32 3, i32 0, i32 1, i32 0} ; [ DW_TAG_lexical_block ] [./basic.c]
+; CHECK: !14 = metadata !{i32 4, i32 0, metadata !4, null}
diff --git a/llvm/test/Transforms/AddDiscriminators/first-only.ll b/llvm/test/Transforms/AddDiscriminators/first-only.ll
new file mode 100644
index 00000000000..f3b0357e576
--- /dev/null
+++ b/llvm/test/Transforms/AddDiscriminators/first-only.ll
@@ -0,0 +1,82 @@
+; RUN: opt < %s -add-discriminators -S | FileCheck %s
+
+; Test that the only instructions that receive a new discriminator in
+; the block 'if.then' are those that share the same line number as
+; the branch in 'entry'.
+;
+; Original code:
+;
+;       void foo(int i) {
+;         int x, y;
+;         if (i < 10) { x = i;
+;             y = -i;
+;         }
+;       }
+
+define void @foo(i32 %i) #0 {
+entry:
+  %i.addr = alloca i32, align 4
+  %x = alloca i32, align 4
+  %y = alloca i32, align 4
+  store i32 %i, i32* %i.addr, align 4
+  %0 = load i32* %i.addr, align 4, !dbg !10
+  %cmp = icmp slt i32 %0, 10, !dbg !10
+  br i1 %cmp, label %if.then, label %if.end, !dbg !10
+
+if.then:                                          ; preds = %entry
+  %1 = load i32* %i.addr, align 4, !dbg !12
+  store i32 %1, i32* %x, align 4, !dbg !12
+
+  %2 = load i32* %i.addr, align 4, !dbg !14
+; CHECK:  %2 = load i32* %i.addr, align 4, !dbg !15
+
+  %sub = sub nsw i32 0, %2, !dbg !14
+; CHECK:  %sub = sub nsw i32 0, %2, !dbg !15
+
+  store i32 %sub, i32* %y, align 4, !dbg !14
+; CHECK:  store i32 %sub, i32* %y, align 4, !dbg !15
+
+  br label %if.end, !dbg !15
+; CHECK:  br label %if.end, !dbg !16
+
+if.end:                                           ; preds = %if.then, %entry
+  ret void, !dbg !16
+; CHECK:  ret void, !dbg !17
+}
+
+attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+!llvm.ident = !{!9}
+
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.5 (trunk 199750) (llvm/trunk 199751)", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [first-only.c] [DW_LANG_C99]
+!1 = metadata !{metadata !"first-only.c", metadata !"."}
+!2 = metadata !{i32 0}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"foo", metadata !"foo", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void (i32)* @foo, null, null, metadata !2, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [foo]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [first-only.c]
+!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !2, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
+!8 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!9 = metadata !{metadata !"clang version 3.5 (trunk 199750) (llvm/trunk 199751)"}
+!10 = metadata !{i32 3, i32 0, metadata !11, null}
+
+!11 = metadata !{i32 786443, metadata !1, metadata !4, i32 3, i32 0, i32 0} ; [ DW_TAG_lexical_block ] [first-only.c]
+; CHECK: !11 = metadata !{i32 786443, metadata !1, metadata !4, i32 3, i32 0, i32 0}
+
+!12 = metadata !{i32 3, i32 0, metadata !13, null}
+
+!13 = metadata !{i32 786443, metadata !1, metadata !11, i32 3, i32 0, i32 1} ; [ DW_TAG_lexical_block ] [first-only.c]
+; CHECK: !13 = metadata !{i32 786443, metadata !1, metadata !14, i32 3, i32 0, i32 1, i32 0} ; [ DW_TAG_lexical_block ] [./first-only.c]
+
+!14 = metadata !{i32 4, i32 0, metadata !13, null}
+; CHECK: !14 = metadata !{i32 786443, metadata !1, metadata !11, i32 3, i32 0, i32 1}
+
+!15 = metadata !{i32 5, i32 0, metadata !13, null}
+; CHECK: !15 = metadata !{i32 4, i32 0, metadata !14, null}
+
+!16 = metadata !{i32 6, i32 0, metadata !4, null}
+; CHECK: !16 = metadata !{i32 5, i32 0, metadata !14, null}
+; CHECK: !17 = metadata !{i32 6, i32 0, metadata !4, null}
+
diff --git a/llvm/test/Transforms/AddDiscriminators/multiple.ll b/llvm/test/Transforms/AddDiscriminators/multiple.ll
new file mode 100644
index 00000000000..0241a0c1a0b
--- /dev/null
+++ b/llvm/test/Transforms/AddDiscriminators/multiple.ll
@@ -0,0 +1,71 @@
+; RUN: opt < %s -add-discriminators -S | FileCheck %s
+
+; Discriminator support for multiple CFG paths on the same line.
+;
+;       void foo(int i) {
+;         int x;
+;         if (i < 10) x = i; else x = -i;
+;       }
+;
+; The two stores inside the if-then-else line must have different discriminator
+; values.
+
+define void @foo(i32 %i) #0 {
+entry:
+  %i.addr = alloca i32, align 4
+  %x = alloca i32, align 4
+  store i32 %i, i32* %i.addr, align 4
+  %0 = load i32* %i.addr, align 4, !dbg !10
+  %cmp = icmp slt i32 %0, 10, !dbg !10
+  br i1 %cmp, label %if.then, label %if.else, !dbg !10
+
+if.then:                                          ; preds = %entry
+  %1 = load i32* %i.addr, align 4, !dbg !10
+; CHECK:  %1 = load i32* %i.addr, align 4, !dbg !12
+
+  store i32 %1, i32* %x, align 4, !dbg !10
+; CHECK:  store i32 %1, i32* %x, align 4, !dbg !12
+
+  br label %if.end, !dbg !10
+; CHECK:  br label %if.end, !dbg !12
+
+if.else:                                          ; preds = %entry
+  %2 = load i32* %i.addr, align 4, !dbg !10
+; CHECK:  %2 = load i32* %i.addr, align 4, !dbg !14
+
+  %sub = sub nsw i32 0, %2, !dbg !10
+; CHECK:  %sub = sub nsw i32 0, %2, !dbg !14
+
+  store i32 %sub, i32* %x, align 4, !dbg !10
+; CHECK:  store i32 %sub, i32* %x, align 4, !dbg !14
+
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  ret void, !dbg !12
+}
+
+attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+!llvm.ident = !{!9}
+
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.5 (trunk 199750) (llvm/trunk 199751)", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [multiple.c] [DW_LANG_C99]
+!1 = metadata !{metadata !"multiple.c", metadata !"."}
+!2 = metadata !{i32 0}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"foo", metadata !"foo", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void (i32)* @foo, null, null, metadata !2, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [foo]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [multiple.c]
+!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !2, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
+!8 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!9 = metadata !{metadata !"clang version 3.5 (trunk 199750) (llvm/trunk 199751)"}
+!10 = metadata !{i32 3, i32 0, metadata !11, null}
+!11 = metadata !{i32 786443, metadata !1, metadata !4, i32 3, i32 0, i32 0} ; [ DW_TAG_lexical_block ] [multiple.c]
+!12 = metadata !{i32 4, i32 0, metadata !4, null}
+
+; CHECK: !12 = metadata !{i32 3, i32 0, metadata !13, null}
+; CHECK: !13 = metadata !{i32 786443, metadata !1, metadata !11, i32 3, i32 0, i32 1, i32 0} ; [ DW_TAG_lexical_block ] [./multiple.c]
+; CHECK: !14 = metadata !{i32 3, i32 0, metadata !15, null}
+; CHECK: !15 = metadata !{i32 786443, metadata !1, metadata !11, i32 3, i32 0, i32 2, i32 1} ; [ DW_TAG_lexical_block ] [./multiple.c]