[PowerPC] Guard against illegal selection of add for TargetConstant operands
r208640 was reverted because it caused a self-hosting failure on ppc64. The
underlying cause was the formation of ISD::ADD nodes with ISD::TargetConstant
operands. Because we have no patterns for 'add' taking 'timm' nodes, these are
selected as r+r add instructions (which is a miscompile). Guard against this
kind of behavior in the future by making the backend crash should this occur
(instead of silently generating invalid output).
llvm-svn: 216897
diff --git a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
index 54ca246..74f6b18 100644
--- a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
@@ -908,6 +908,13 @@
return nullptr; // Already selected.
}
+ // In case any misguided DAG-level optimizations form an ADD with a
+ // TargetConstant operand, crash here instead of miscompiling (by selecting
+ // an r+r add instead of some kind of r+i add).
+ if (N->getOpcode() == ISD::ADD &&
+ N->getOperand(1).getOpcode() == ISD::TargetConstant)
+ llvm_unreachable("Invalid ADD with TargetConstant operand");
+
switch (N->getOpcode()) {
default: break;