Erase constant dbgloc on reuse in PHI node

Basic block selection involves checking successor BBs for PHI nodes
that depend on the current BB.  In case such BBs are found, the value
being selected is a constant and such constant already exists in
current BB, it's value is reused.

This might lead to wrong locations in some situations, especially if
same constant value ends up being materialized twice in two different
ways, which discards that sharing and leaves us with wrong debug
location in the successor BB.

In code this involves the following sequence of calls:

 SelectionDAGBuilder::HandlePHINodesInSuccessorBlocks ->
 SelectionDAGBuilder::CopyValueToVirtualRegister ->
 SelectionDAGBuilder::getNonRegisterValue

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239089 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index a0eea9ffb0686507b2b70471ab24b9490109fc5b..cf0900f59e857080f112fcec0c4266fc5d7cac31 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1002,7 +1002,16 @@ bool SelectionDAGBuilder::findValue(const Value *V) const {
 SDValue SelectionDAGBuilder::getNonRegisterValue(const Value *V) {
   // If we already have an SDValue for this value, use it.
   SDValue &N = NodeMap[V];
-  if (N.getNode()) return N;
+  if (N.getNode()) {
+    if (isa<ConstantSDNode>(N) || isa<ConstantFPSDNode>(N)) {
+      // Remove the debug location from the node as the node is about to be used
+      // in a location which may differ from the original debug location.  This
+      // is relevant to Constant and ConstantFP nodes because they can appear
+      // as constant expressions inside PHI nodes.
+      N->setDebugLoc(DebugLoc());
+    }
+    return N;
+  }
 
   // Otherwise create a new SDValue and remember it.
   SDValue Val = getValueImpl(V);

diff --git a/test/DebugInfo/X86/inlined-indirect-value.ll b/test/DebugInfo/X86/inlined-indirect-value.ll
new file mode 100644 (file)
index 0000000..7f95691
--- /dev/null
+++ b/test/DebugInfo/X86/inlined-indirect-value.ll
@@ -0,0 +1,81 @@
+; RUN: llc -filetype=asm -asm-verbose=0 < %s | FileCheck %s
+
+; "1" from line 09 in the snippet below shouldn't be marked with location of "1"
+; from line 04.  Instead it will have location inside main() (real location is
+; just erased, so it won't be perfectly accurate).
+
+; options: -g -O3
+; 01 volatile int x;
+; 02 int y;
+; 03 static __attribute__((always_inline)) int f1() {
+; 04     if (x * 3 < 14) return 1;
+; 05     return 2;
+; 06 }
+; 07 int main() {
+; 08     x = f1();
+; 09     x = x ? 1 : 2;
+; 10 }
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@x = common global i32 0, align 4
+@y = common global i32 0, align 4
+
+define i32 @main() {
+; CHECK: .loc 1 {{[89]}}
+; CHECK-NOT: .loc
+; CHECK: movl $1
+
+entry:
+  %0 = load volatile i32, i32* @x, align 4, !dbg !16, !tbaa !19
+  %mul.i = mul nsw i32 %0, 3, !dbg !23
+  %cmp.i = icmp slt i32 %mul.i, 14, !dbg !24
+  %..i = select i1 %cmp.i, i32 1, i32 2, !dbg !25
+  store volatile i32 %..i, i32* @x, align 4, !dbg !27, !tbaa !19
+  %1 = load volatile i32, i32* @x, align 4, !dbg !28, !tbaa !19
+  %tobool = icmp ne i32 %1, 0, !dbg !28
+  br i1 %tobool, label %select.end, label %select.mid
+
+select.mid:                                       ; preds = %entry
+  br label %select.end
+
+select.end:                                       ; preds = %entry, %select.mid
+  %cond = phi i32 [ 1, %entry ], [ 2, %select.mid ]
+  store volatile i32 %cond, i32* @x, align 4, !dbg !29, !tbaa !19
+  ret i32 0, !dbg !30
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!13, !14}
+
+!0 = !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "", isOptimized: true, runtimeVersion: 0, emissionKind: 1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !9, imports: !2)
+!1 = !DIFile(filename: "inline-break.c", directory: "/build/dir")
+!2 = !{}
+!3 = !{!4, !8}
+!4 = !DISubprogram(name: "main", scope: !1, file: !1, line: 7, type: !5, isLocal: false, isDefinition: true, scopeLine: 7, isOptimized: true, function: i32 ()* @main, variables: !2)
+!5 = !DISubroutineType(types: !6)
+!6 = !{!7}
+!7 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!8 = !DISubprogram(name: "f1", scope: !1, file: !1, line: 3, type: !5, isLocal: true, isDefinition: true, scopeLine: 3, isOptimized: true, variables: !2)
+!9 = !{!10, !12}
+!10 = !DIGlobalVariable(name: "x", scope: !0, file: !1, line: 1, type: !11, isLocal: false, isDefinition: true, variable: i32* @x)
+!11 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !7)
+!12 = !DIGlobalVariable(name: "y", scope: !0, file: !1, line: 2, type: !7, isLocal: false, isDefinition: true, variable: i32* @y)
+!13 = !{i32 2, !"Dwarf Version", i32 4}
+!14 = !{i32 2, !"Debug Info Version", i32 3}
+!16 = !DILocation(line: 4, column: 9, scope: !17, inlinedAt: !18)
+!17 = distinct !DILexicalBlock(scope: !8, file: !1, line: 4, column: 9)
+!18 = distinct !DILocation(line: 8, column: 9, scope: !4)
+!19 = !{!20, !20, i64 0}
+!20 = !{!"int", !21, i64 0}
+!21 = !{!"omnipotent char", !22, i64 0}
+!22 = !{!"Simple C/C++ TBAA"}
+!23 = !DILocation(line: 4, column: 11, scope: !17, inlinedAt: !18)
+!24 = !DILocation(line: 4, column: 15, scope: !17, inlinedAt: !18)
+!25 = !DILocation(line: 4, column: 21, scope: !26, inlinedAt: !18)
+!26 = !DILexicalBlockFile(scope: !17, file: !1, discriminator: 1)
+!27 = !DILocation(line: 8, column: 7, scope: !4)
+!28 = !DILocation(line: 9, column: 9, scope: !4)
+!29 = !DILocation(line: 9, column: 7, scope: !4)
+!30 = !DILocation(line: 10, column: 1, scope: !4)