Fix a (u)comiss intrinsic lowering bug. It was using anyext which can return junk in higher bits. Patch by Nate Begeman.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54903 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index b76d3e2..2bd875e 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1515,6 +1515,8 @@
       SDValue N0 = Node->getOperand(0);
       // Get the subregsiter index for the type to extend.
       MVT N0VT = N0.getValueType();
+      // FIXME: In x86-32, 8-bit value may be in AH, etc. which don't have
+      // super-registers.
       unsigned Idx = (N0VT == MVT::i32) ? X86::SUBREG_32BIT :
                       (N0VT == MVT::i16) ? X86::SUBREG_16BIT :
                         (Subtarget->is64Bit()) ? X86::SUBREG_8BIT : 0;