Remind ourselves to revisit the "pxor vs. xorps/xorpd to clear XMM registers"

issue. Need to do more experiments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26247 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index b794176fa537851bad2be77498518ac070a765d7..5a2da2d3d26af6c304515b372f0c664b5d886e50 100644 (file)
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -437,3 +437,9 @@ It might be better to generate
        movw al, 8(%edx)
        
 when we can spare a register. It reduces code size.
+
+//===---------------------------------------------------------------------===//
+
+It's not clear whether we should use pxor or xorps / xorpd to clear XMM
+registers. The choice may depend on subtarget information. We should do some
+more experiments on different x86 machines.