Remove invalid assert in DAGTypeLegalizer::RemapValue

There is a comment at the top of DAGTypeLegalizer::PerformExpensiveChecks
which, in part, says:

  // Note that these invariants may not hold momentarily when processing a node:
  // the node being processed may be put in a map before being marked Processed.

Unfortunately, this assert would be valid only if the above-mentioned invariant
held unconditionally. This was causing llc to assert when, in fact,
everything was fine.

Thanks to Richard Sandiford for investigating this issue!

Fixes PR16562.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186338 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 61 insertions, 1 deletions

diff --git a/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp b/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
index ef79662..fd770d1 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
@@ -615,7 +615,10 @@ void DAGTypeLegalizer::RemapValue(SDValue &N) {
     // replaced with other values.
     RemapValue(I->second);
     N = I->second;
-    assert(N.getNode()->getNodeId() != NewNode && "Mapped to new node!");
+
+    // Note that it is possible to have N.getNode()->getNodeId() == NewNode at
+    // this point because it is possible for a node to be put in the map before
+    // being processed.
   }
 }
 
diff --git a/test/CodeGen/PowerPC/remap-crash.ll b/test/CodeGen/PowerPC/remap-crash.ll
new file mode 100644
index 0000000..515f720
--- /dev/null
+++ b/test/CodeGen/PowerPC/remap-crash.ll
@@ -0,0 +1,57 @@
+; RUN: llc -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 < %s
+target triple = "powerpc64-unknown-linux-gnu"
+
+define void @autogen_SD13() {
+BB:
+  br label %CF78
+
+CF78:                                             ; preds = %CF87, %CF86, %CF78, %BB
+  %Cmp = icmp ule <16 x i64> zeroinitializer, zeroinitializer
+  br i1 undef, label %CF78, label %CF86
+
+CF86:                                             ; preds = %CF78
+  br i1 undef, label %CF78, label %CF84
+
+CF84:                                             ; preds = %CF84, %CF86
+  br i1 undef, label %CF84, label %CF87
+
+CF87:                                             ; preds = %CF84
+  br i1 undef, label %CF78, label %CF82
+
+CF82:                                             ; preds = %CF82, %CF87
+  br i1 undef, label %CF82, label %CF83
+
+CF83:                                             ; preds = %CF82
+  br label %CF
+
+CF:                                               ; preds = %CF80, %CF81, %CF, %CF83
+  br i1 undef, label %CF, label %CF81
+
+CF81:                                             ; preds = %CF
+  %Se = sext <16 x i1> %Cmp to <16 x i16>
+  br i1 undef, label %CF, label %CF80
+
+CF80:                                             ; preds = %CF81
+  br i1 undef, label %CF, label %CF76
+
+CF76:                                             ; preds = %CF76, %CF80
+  %Sl58 = select i1 undef, <16 x i16> %Se, <16 x i16> %Se
+  br label %CF76
+}
+
+define void @autogen_SD1067() {
+BB:
+  %FC = sitofp <4 x i32> zeroinitializer to <4 x ppc_fp128>
+  br label %CF77
+
+CF77:                                             ; preds = %CF77, %BB
+  %brmerge = or i1 false, undef
+  br i1 %brmerge, label %CF77, label %CF85
+
+CF85:                                             ; preds = %CF77
+  %Shuff19 = shufflevector <4 x ppc_fp128> %FC, <4 x ppc_fp128> %FC, <4 x i32> <i32 7, i32 1, i32 3, i32 5>
+  br label %CF75
+
+CF75:                                             ; preds = %CF75, %CF85
+  br label %CF75
+}