[llvm] r234079 - [X86] Add a comment about the change in r234075.

[Craig Topper]

Author: ctopper
Date: Fri Apr  3 21:31:43 2015
New Revision: 234079

URL: http://llvm.org/viewvc/llvm-project?rev=234079&view=rev
Log:
[X86] Add a comment about the change in r234075.

Modified:
    llvm/trunk/lib/Target/X86/X86InstrCompiler.td

Modified: llvm/trunk/lib/Target/X86/X86InstrCompiler.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrCompiler.td?rev=234079&r1=234078&r2=234079&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrCompiler.td (original)
+++ llvm/trunk/lib/Target/X86/X86InstrCompiler.td Fri Apr  3 21:31:43 2015
@@ -1232,6 +1232,8 @@ def : Pat<(store (add (loadi64 addr:$dst
 // with implicit zero-extension instead of a 64-bit and if the immediate has at
 // least 32 bits of leading zeros. If in addition the last 32 bits can be
 // represented with a sign extension of a 8 bit constant, use that.
+// This can also reduce instruction size by eliminating the need for the REX
+// prefix.
 
 let AddedComplexity = 1 in // Give priority over i64immSExt8.
 def : Pat<(and GR64:$src, i64immZExt32SExt8:$imm),