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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105341 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index bb80ace..a322ad2 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -980,6 +980,17 @@
setOperationAction(ISD::SSUBO, MVT::i32, Custom);
setOperationAction(ISD::USUBO, MVT::i32, Custom);
setOperationAction(ISD::SMULO, MVT::i32, Custom);
+
+ // Don't try to custom-lower 64-bit add-with-overflow and friends
+ // on x86-32; the x86 backend currently doesn't know how to handle them.
+ //
+ // This doesn't really fix anything because LegalizeTypes doesn't know
+ // how to handle them either. We do get a better error message, though.
+ //
+ // This may not be hard to implement though.
+ // In fact you could even cheat, and turn the 64 bit add-with-overflow
+ // into a 65 bit add, with the top bit being used to compute the overflow
+ // flag. That should then all get expanded out automagically.
if (Subtarget->is64Bit()) {
setOperationAction(ISD::SADDO, MVT::i64, Custom);
setOperationAction(ISD::UADDO, MVT::i64, Custom);