Fix PR12821.
RAFast must add an <imp-def> operand when it is rewriting a sub-register
def that isn't a read-modify-write.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156777 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocFast.cpp b/lib/CodeGen/RegAllocFast.cpp
index 70fbfd4..15485b1 100644
--- a/lib/CodeGen/RegAllocFast.cpp
+++ b/lib/CodeGen/RegAllocFast.cpp
@@ -674,6 +674,12 @@
MI->addRegisterKilled(PhysReg, TRI, true);
return true;
}
+
+ // A <def,read-undef> of a sub-register requires an implicit def of the full
+ // register.
+ if (MO.isDef() && MO.isUndef())
+ MI->addRegisterDefined(PhysReg, TRI);
+
return MO.isDead();
}