[X86] Fix Stale SDNode use in X86ISelDAGtoDAG

[niravd]

Summary

Fixes pr32329.

[chandlerc]

The fix seems trivial and looks good. Please submit to at least fix the crasher.

One note for this and future, similar patches: can you minimize the test case any? At the least stripping off some of the metadata cruft and comment boiler plate would be good.

Also, please always run FileCheck and assert that reasonable instructions are generated. "doesn't crash" isn't the most useful test case, and small cases like this should be easy to check that sane instructions come out.

lib/Target/X86/X86ISelDAGToDAG.cpp

case ISD::SUB: {
 
     // Ok, the transformation is legal and appears profitable. Go for it.
     SDValue Zero = CurDAG->getConstant(0, dl, N.getValueType());
     SDValue Neg = CurDAG->getNode(ISD::SUB, dl, N.getValueType(), Zero, RHS);
     AM.IndexReg = Neg;
     AM.Scale = 1;
 
     // Insert the new nodes into the topological ordering.
-    insertDAGNode(*CurDAG, N, Zero);
-    insertDAGNode(*CurDAG, N, Neg);
+    insertDAGNode(*CurDAG, Handle.getValue(), Zero);
+    insertDAGNode(*CurDAG, Handle.getValue(), Neg);
     return false;
   }
 
   case ISD::ADD:
     if (!matchAdd(N, AM, Depth))
       return false;
     break;
 

test/CodeGen/X86/pr32329.ll

+; RUN: llc -mtriple=i686-unknown -mcpu=skx %s -o -
+; RUN: llc -mtriple=x86_64-unknown -mcpu=skx %s -o -
+
+%struct.AA = type { i24, [4 x i8] }
+
+@obj = external local_unnamed_addr global %struct.AA, align 8
+@var_27 = external local_unnamed_addr constant i8, align 1
+@var_2 = external local_unnamed_addr constant i16, align 2
+@var_24 = external local_unnamed_addr constant i64, align 8
+@var_310 = external local_unnamed_addr global i64, align 8
+@var_50 = external local_unnamed_addr global i64, align 8
+@var_205 = external local_unnamed_addr global i8, align 1
+@var_218 = external local_unnamed_addr global i8, align 1
+
+; Function Attrs: norecurse nounwind uwtable
+;define void @foo() local_unnamed_addr {
+define void @_Z3foov() local_unnamed_addr #0 {
+  entry:     
+  %bf.load = load i32, i32* bitcast (%struct.AA* @obj to i32*), align 8
+  %bf.clear = shl i32 %bf.load, 1
+  %add = and i32 %bf.clear, 8388606
+  %0 = load i8, i8* @var_27, align 1, !tbaa !1
+  %conv5 = sext i8 %0 to i32
+  %sub = sub nsw i32 %add, %conv5
+  %1 = load i16, i16* @var_2, align 2, !tbaa !4
+  %conv6 = zext i16 %1 to i32
+  %sub7 = sub nsw i32 %sub, %conv6
+  %conv8 = sext i32 %sub7 to i64
+  %2 = load i64, i64* @var_24, align 8, !tbaa !6
+  %3 = load i64, i64* @var_310, align 8, !tbaa !6
+  %conv9 = sext i8 %0 to i64
+  %mul = mul i64 %3, %conv9
+  %add10 = add i64 %mul, %2
+  %mul11 = mul i64 %add10, %conv8
+  %sub12 = add i64 %mul11, 8662905354777116273
+  %shl = shl i64 9, %sub12
+  store i64 %shl, i64* @var_50, align 8, !tbaa !6
+  %bf.clear14 = and i32 %bf.load, 4194303
+  %add21 = shl nuw nsw i32 %bf.clear14, 1
+  %sub23 = sub nsw i32 %add21, %conv5
+  %sub25 = sub nsw i32 %sub23, %conv6
+  %cmp = icmp sge i32 %sub25, %bf.clear14
+  %conv30 = zext i1 %cmp to i8
+  store i8 %conv30, i8* @var_205, align 1, !tbaa !1
+  %mul43 = mul nsw i32 %sub, %conv5
+  %conv44 = trunc i32 %mul43 to i8
+  store i8 %conv44, i8* @var_218, align 1, !tbaa !1
+  ret void
+}
+
+attributes #0 = { "target-cpu"="skx" }
+
+!llvm.ident = !{!0}
+
+!0 = !{!"clang version 5.0.0 (trunk 298511) (llvm/trunk 298531)"}
+!1 = !{!2, !2, i64 0}
+!2 = !{!"omnipotent char", !3, i64 0}
+!3 = !{!"Simple C++ TBAA"}
+!4 = !{!5, !5, i64 0}
+!5 = !{!"short", !2, i64 0}
+!6 = !{!7, !7, i64 0}
+!7 = !{!"long long", !2, i64 0}