DebugInfo: Avoid propagating incorrect debug locations in SelectionDAG via CSE.

Summary:
When SelectionDAG performs CSE it is possible that the context's source
location is different from that of the selected node. This can lead to
incorrect line number records. We update the debug location to the
one that occurs earlier in the instruction sequence.

This fixes PR21006.

Reviewers: echristo, sdmitrouk

Subscribers: jevinskie, asl, llvm-commits

Differential Revision: http://reviews.llvm.org/D12094

llvm-svn: 268323

1 files changed, 100 insertions, 0 deletions

diff --git a/llvm/test/DebugInfo/Generic/isel-cse-line.ll b/llvm/test/DebugInfo/Generic/isel-cse-line.ll
new file mode 100644
index 00000000000..dfb058bea5b
--- /dev/null
+++ b/llvm/test/DebugInfo/Generic/isel-cse-line.ll
@@ -0,0 +1,100 @@
+; RUN: llc -filetype=asm -fast-isel=false -O0 < %s | FileCheck %s
+;
+; Generated by:
+; clang -emit-llvm -S -g test.cpp
+
+; typedef double         fp_t;
+; typedef unsigned long  int_t;
+;
+; int_t glb_start      = 17;
+; int_t glb_end        = 42;
+;
+; int main()
+; {
+;   int_t start = glb_start;
+;   int_t end   = glb_end;
+;
+;   fp_t dbl_start = (fp_t) start;
+;   fp_t dbl_end   = (fp_t) end;
+;
+;   return 0;
+; }
+
+; SelectionDAG performs CSE on constant pool loads. Make sure line numbers
+; from such nodes are not propagated. Doing so results in oscillating line numbers.
+
+; CHECK: .loc 1 12
+; CHECK: .loc 1 13
+; CHECK-NOT: .loc 1 12
+
+; ModuleID = 't.cpp'
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@glb_start = global i64 17, align 8
+@glb_end = global i64 42, align 8
+
+; Function Attrs: norecurse nounwind uwtable
+define i32 @main() !dbg !14 {
+  %1 = alloca i32, align 4
+  %2 = alloca i64, align 8
+  %3 = alloca i64, align 8
+  %4 = alloca double, align 8
+  %5 = alloca double, align 8
+  store i32 0, i32* %1, align 4
+  call void @llvm.dbg.declare(metadata i64* %2, metadata !18, metadata !19), !dbg !20
+  %6 = load i64, i64* @glb_start, align 8, !dbg !21
+  store i64 %6, i64* %2, align 8, !dbg !20
+  call void @llvm.dbg.declare(metadata i64* %3, metadata !22, metadata !19), !dbg !23
+  %7 = load i64, i64* @glb_end, align 8, !dbg !24
+  store i64 %7, i64* %3, align 8, !dbg !23
+  call void @llvm.dbg.declare(metadata double* %4, metadata !25, metadata !19), !dbg !26
+  %8 = load i64, i64* %2, align 8, !dbg !27
+  %9 = uitofp i64 %8 to double, !dbg !27
+  store double %9, double* %4, align 8, !dbg !26
+  call void @llvm.dbg.declare(metadata double* %5, metadata !28, metadata !19), !dbg !29
+  %10 = load i64, i64* %3, align 8, !dbg !30
+  %11 = uitofp i64 %10 to double, !dbg !30
+  store double %11, double* %5, align 8, !dbg !29
+  ret i32 0, !dbg !31
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!11, !12}
+!llvm.ident = !{!13}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.9.0 (trunk 268246)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, globals: !6)
+!1 = !DIFile(filename: "/home/wpieb/test/D12094.cpp", directory: "/home/wpieb/build/llvm/trunk/llvm-RelWithDebInfo")
+!2 = !{}
+!3 = !{!4}
+!4 = !DIDerivedType(tag: DW_TAG_typedef, name: "fp_t", file: !1, line: 1, baseType: !5)
+!5 = !DIBasicType(name: "double", size: 64, align: 64, encoding: DW_ATE_float)
+!6 = !{!7, !10}
+!7 = distinct !DIGlobalVariable(name: "glb_start", scope: !0, file: !1, line: 4, type: !8, isLocal: false, isDefinition: true, variable: i64* @glb_start)
+!8 = !DIDerivedType(tag: DW_TAG_typedef, name: "int_t", file: !1, line: 2, baseType: !9)
+!9 = !DIBasicType(name: "long unsigned int", size: 64, align: 64, encoding: DW_ATE_unsigned)
+!10 = distinct !DIGlobalVariable(name: "glb_end", scope: !0, file: !1, line: 5, type: !8, isLocal: false, isDefinition: true, variable: i64* @glb_end)
+!11 = !{i32 2, !"Dwarf Version", i32 4}
+!12 = !{i32 2, !"Debug Info Version", i32 3}
+!13 = !{!"clang version 3.9.0 (trunk 268246)"}
+!14 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 7, type: !15, isLocal: false, isDefinition: true, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!15 = !DISubroutineType(types: !16)
+!16 = !{!17}
+!17 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!18 = !DILocalVariable(name: "start", scope: !14, file: !1, line: 9, type: !8)
+!19 = !DIExpression()
+!20 = !DILocation(line: 9, column: 9, scope: !14)
+!21 = !DILocation(line: 9, column: 17, scope: !14)
+!22 = !DILocalVariable(name: "end", scope: !14, file: !1, line: 10, type: !8)
+!23 = !DILocation(line: 10, column: 9, scope: !14)
+!24 = !DILocation(line: 10, column: 17, scope: !14)
+!25 = !DILocalVariable(name: "dbl_start", scope: !14, file: !1, line: 12, type: !4)
+!26 = !DILocation(line: 12, column: 8, scope: !14)
+!27 = !DILocation(line: 12, column: 27, scope: !14)
+!28 = !DILocalVariable(name: "dbl_end", scope: !14, file: !1, line: 13, type: !4)
+!29 = !DILocation(line: 13, column: 8, scope: !14)
+!30 = !DILocation(line: 13, column: 27, scope: !14)
+!31 = !DILocation(line: 15, column: 3, scope: !14)