diff options
| -rw-r--r-- | lib/Target/X86/X86ISelDAGToDAG.cpp | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp index b079281..9465420 100644 --- a/lib/Target/X86/X86ISelDAGToDAG.cpp +++ b/lib/Target/X86/X86ISelDAGToDAG.cpp @@ -2531,6 +2531,11 @@ SDNode *X86DAGToDAGISel::Select(SDNode *Node) { // Prevent use of AH in a REX instruction by referencing AX instead. // Shift it down 8 bits. + // + // The current assumption of the register allocator is that isel + // won't generate explicit references to the GPR8_NOREX registers. If + // the allocator and/or the backend get enhanced to be more robust in + // that regard, this can be, and should be, removed. if (HiReg == X86::AH && Subtarget->is64Bit() && !SDValue(Node, 1).use_empty()) { SDValue Result = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), dl, |