Fix PR24563 (LiveDebugVariables unconditionally propagates all DBG_VALUEs)

LiveDebugVariables unconditionally propagates all DBG_VALUE down the
dominator tree, which happens to work fine if there already is another
DBG_VALUE or the DBG_VALUE happends to describe a single-assignment vreg
but is otherwise wrong if the DBG_VALUE is coming from only one of the
predecessors.

In r255759 we introduced a proper data flow analysis scheduled after
LiveDebugVariables that correctly propagates DBG_VALUEs across basic block
boundaries. With the new pass in place, the incorrect propagation in
LiveDebugVariables can be retired witout loosing any of the benefits
where LiveDebugVariables happened to do the right thing.

llvm-svn: 256188

1 files changed, 101 insertions, 0 deletions

diff --git a/llvm/test/DebugInfo/X86/bbjoin.ll b/llvm/test/DebugInfo/X86/bbjoin.ll
new file mode 100644
index 00000000000..8061a8d2ce9
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/bbjoin.ll
@@ -0,0 +1,101 @@
+; RUN: llc -mtriple=x86_64-apple-macosx10.9.0 %s -stop-after=livedebugvars \
+; RUN:   -o %t.s | FileCheck %s
+; Generated from:
+; void g(int *);
+; int f() {
+;   int x = 23;
+;   g(&x);
+;   if (x == 42)
+;     ++x;
+;   return x; // check that x is not a constant here.
+; }
+; CHECK: ![[X:.*]] = !DILocalVariable(name: "x",
+; CHECK: bb.0.entry:
+; CHECK:   DBG_VALUE 23, 0, ![[X]],
+; CHECK:   DBG_VALUE debug-use %rdi, debug-use _, ![[X]]
+; CHECK: bb.1.if.then:
+; CHECK:   DBG_VALUE debug-use %rdi, debug-use _, ![[X]],
+; CHECK: bb.2.if.end:
+; CHECK-NOT:  DBG_VALUE 23, 0, ![[X]],
+; CHECK:   RETQ %eax
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.11.0"
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @f() #0 !dbg !4 {
+entry:
+  %x = alloca i32, align 4
+  %0 = bitcast i32* %x to i8*, !dbg !14
+  call void @llvm.lifetime.start(i64 4, i8* %0) #4, !dbg !14
+  tail call void @llvm.dbg.value(metadata i32 23, i64 0, metadata !9, metadata !15), !dbg !16
+  store i32 23, i32* %x, align 4, !dbg !16, !tbaa !17
+  tail call void @llvm.dbg.value(metadata i32* %x, i64 0, metadata !9, metadata !15), !dbg !16
+  call void @g(i32* nonnull %x) #4, !dbg !21
+  call void @llvm.dbg.value(metadata i32* %x, i64 0, metadata !9, metadata !15), !dbg !16
+  %1 = load i32, i32* %x, align 4, !dbg !22, !tbaa !17
+  %cmp = icmp eq i32 %1, 42, !dbg !24
+  br i1 %cmp, label %if.then, label %if.end, !dbg !25
+
+if.then:                                          ; preds = %entry
+  call void @llvm.dbg.value(metadata i32 43, i64 0, metadata !9, metadata !15), !dbg !16
+  store i32 43, i32* %x, align 4, !dbg !26, !tbaa !17
+  br label %if.end, !dbg !26
+
+if.end:                                           ; preds = %if.then, %entry
+  %2 = phi i32 [ 43, %if.then ], [ %1, %entry ], !dbg !27
+  call void @llvm.dbg.value(metadata i32* %x, i64 0, metadata !9, metadata !15), !dbg !16
+  call void @llvm.lifetime.end(i64 4, i8* %0) #4, !dbg !28
+  ret i32 %2, !dbg !29
+}
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.start(i64, i8* nocapture) #1
+
+declare void @g(i32*) #4
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.end(i64, i8* nocapture) #1
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #3
+
+attributes #0 = { nounwind ssp uwtable }
+attributes #1 = { argmemonly nounwind }
+attributes #3 = { nounwind readnone }
+attributes #4 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!10, !11, !12}
+!llvm.ident = !{!13}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.8.0 (trunk 255890) (llvm/trunk 255919)", isOptimized: true, runtimeVersion: 0, emissionKind: 1, enums: !2, subprograms: !3)
+!1 = !DIFile(filename: "constant.c", directory: "")
+!2 = !{}
+!3 = !{!4}
+!4 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 2, type: !5, isLocal: false, isDefinition: true, scopeLine: 2, isOptimized: true, variables: !8)
+!5 = !DISubroutineType(types: !6)
+!6 = !{!7}
+!7 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!8 = !{!9}
+!9 = !DILocalVariable(name: "x", scope: !4, file: !1, line: 3, type: !7)
+!10 = !{i32 2, !"Dwarf Version", i32 2}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"PIC Level", i32 2}
+!13 = !{!"clang version 3.8.0 (trunk 255890) (llvm/trunk 255919)"}
+!14 = !DILocation(line: 3, column: 3, scope: !4)
+!15 = !DIExpression()
+!16 = !DILocation(line: 3, column: 7, scope: !4)
+!17 = !{!18, !18, i64 0}
+!18 = !{!"int", !19, i64 0}
+!19 = !{!"omnipotent char", !20, i64 0}
+!20 = !{!"Simple C/C++ TBAA"}
+!21 = !DILocation(line: 4, column: 3, scope: !4)
+!22 = !DILocation(line: 5, column: 7, scope: !23)
+!23 = distinct !DILexicalBlock(scope: !4, file: !1, line: 5, column: 7)
+!24 = !DILocation(line: 5, column: 9, scope: !23)
+!25 = !DILocation(line: 5, column: 7, scope: !4)
+!26 = !DILocation(line: 6, column: 5, scope: !23)
+!27 = !DILocation(line: 7, column: 10, scope: !4)
+!28 = !DILocation(line: 8, column: 1, scope: !4)
+!29 = !DILocation(line: 7, column: 3, scope: !4)