Clarify that CALLSEQ_START..END may not be nested,
and add some protection against creating such.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47957 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h
index afd1e78..025e9ec 100644
--- a/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -529,6 +529,7 @@
// a call sequence, and carry arbitrary information that target might want
// to know. The first operand is a chain, the rest are specified by the
// target and not touched by the DAG optimizers.
+ // CALLSEQ_START..CALLSEQ_END pairs may not be nested.
CALLSEQ_START, // Beginning of a call sequence
CALLSEQ_END, // End of a call sequence
diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 82324cd..fd9cf15 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -1266,6 +1266,13 @@
// The only option for this is to custom lower it.
Tmp3 = TLI.LowerOperation(Result.getValue(0), DAG);
assert(Tmp3.Val && "Target didn't custom lower this node!");
+ // A call within a calling sequence must be legalized to something
+ // other than the normal CALLSEQ_END. Violating this gets Legalize
+ // into an infinite loop.
+ assert ((!IsLegalizingCall ||
+ Node->getOpcode() != ISD::CALL ||
+ Tmp3.Val->getOpcode() != ISD::CALLSEQ_END) &&
+ "Nested CALLSEQ_START..CALLSEQ_END not supported.");
// The number of incoming and outgoing values should match; unless the final
// outgoing value is a flag.