add a simple hack

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45343 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index 8effd47766b4dd560a1bc3102a76eda7ed0705f7..ad15b14f16660ccb51913a7639d51aad709e4f0c 100644 (file)
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -1573,3 +1573,15 @@ _test:
 
 //===---------------------------------------------------------------------===//
 
+We can fold a store into "zeroing a reg".  Instead of:
+
+xorl    %eax, %eax
+movl    %eax, 124(%esp)
+
+we should get:
+
+movl    $0, 124(%esp)
+
+if the flags of the xor are dead.
+
+//===---------------------------------------------------------------------===//