[SelectionDAG] Transfer DbgValues when casts are optimized in SelectionDAG::getNode

[asmith]

Summary

getNode optimizes (ext (trunc x)) to x and the dbgvalue node on trunc is lost. The fix calls transferDbgValues to add the dbgvalue to x.

Add DebugInfo/AArch64/dbg-value-i16.ll

Patch by Sejong Oh!

[aprantl]

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

3965

typo?

[vsk]

Thanks for the patch! Could you upload a diff with context (git diff -U10000)?

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

3969

Why is InvalidateDbg false? Does the debug value attached to Operand need to remain valid after it's cloned and attached to OpOp?

[vsk]

LGTM, thanks!

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

case ISD::ANY_EXTEND:
 
     if (OpOpcode == ISD::ZERO_EXTEND || OpOpcode == ISD::SIGN_EXTEND ||
         OpOpcode == ISD::ANY_EXTEND)
       // (ext (zext x)) -> (zext x)  and  (ext (sext x)) -> (sext x)
       return getNode(OpOpcode, DL, VT, Operand.getOperand(0));
     else if (OpOpcode == ISD::UNDEF)
       return getUNDEF(VT);
 
-    // (ext (trunx x)) -> x
+    // (ext (trunc x)) -> x
     if (OpOpcode == ISD::TRUNCATE) {
       SDValue OpOp = Operand.getOperand(0);
-      if (OpOp.getValueType() == VT)
+      if (OpOp.getValueType() == VT) {
+        transferDbgValues(Operand, OpOp);
         return OpOp;
       }
+    }
     break;
   case ISD::TRUNCATE:
     assert(VT.isInteger() && Operand.getValueType().isInteger() &&
            "Invalid TRUNCATE!");
     if (Operand.getValueType() == VT) return Operand;   // noop truncate
     assert((!VT.isVector() ||
             VT.getVectorNumElements() ==
             Operand.getValueType().getVectorNumElements()) &&

test/DebugInfo/AArch64/dbg-value-i16.ll

+; RUN: llc -stop-after=livedebugvalues < %s | FileCheck %s
+;
+; ModuleID = 'dbg-value-i16.ll'
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64"
+
+; CHECK: DBG_VALUE
+; Function Attrs: nounwind 
+define void @f() #0 !dbg !4 {
+entry:
+  tail call void @h(i16 0) #2, !dbg !14
+  %call = tail call i16 (...) @g() #2, !dbg !15
+  tail call void @llvm.dbg.value(metadata i16 %call, metadata !8, metadata !16), !dbg !17
+  tail call void @h(i16 %call) #2, !dbg !18
+  ret void, !dbg !19
+}
+
+declare void @h(i16)
+
+declare i16 @g(...)
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind readnone }
+attributes #2 = { 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 3.9.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "test.c", directory: "/Volumes/Data/llvm")
+!2 = !{}
+!4 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: true, unit: !0, variables: !7)
+!5 = !DISubroutineType(types: !6)
+!6 = !{null}
+!7 = !{!8}
+!8 = !DILocalVariable(name: "a", scope: !4, file: !1, line: 5, type: !9)
+!9 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!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 3.9.0 "}
+!14 = !DILocation(line: 4, column: 3, scope: !4)
+!15 = !DILocation(line: 5, column: 11, scope: !4)
+!16 = !DIExpression()
+!17 = !DILocation(line: 5, column: 7, scope: !4)
+!18 = !DILocation(line: 6, column: 3, scope: !4)
+!19 = !DILocation(line: 7, column: 1, scope: !4)