Add a entry.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26173 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index 3bbf3c26e413006a647450c17dea449209b97ce4..50d87bc173a27d430c27ed1b41e605687c94f277 100644 (file)
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -426,3 +426,20 @@ When: "movl $_dst, _ptr" is sufficient.
 //===---------------------------------------------------------------------===//
 
 Use fisttp to do FP to integer conversion whenever it is available.
+
+//===---------------------------------------------------------------------===//
+
+Instead of the following for memset char*, 1, 10:
+
+       movl $16843009, 4(%edx)
+       movl $16843009, (%edx)
+       movw $257, 8(%edx)
+
+It might be better to generate
+
+       movl $16843009, %eax
+       movl %eax, 4(%edx)
+       movl %eax, (%edx)
+       movw al, 8(%edx)
+       
+when we can spare a register. It reduces code size.