[llvm-commits] [llvm] r50681 - /llvm/trunk/lib/Target/X86/README.txt

[Chris Lattner]

Author: lattner
Date: Mon May  5 18:19:45 2008
New Revision: 50681

URL: http://llvm.org/viewvc/llvm-project?rev=50681&view=rev
Log:
add a micro optzn.

Modified:
    llvm/trunk/lib/Target/X86/README.txt

Modified: llvm/trunk/lib/Target/X86/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/README.txt?rev=50681&r1=50680&r2=50681&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Mon May  5 18:19:45 2008
@@ -1691,3 +1691,21 @@
   ...
 
 //===---------------------------------------------------------------------===//
+
+We compile:
+
+int test(int x, int y) {
+  return x-y-1;
+}
+
+into (-m64):
+
+_test:
+	decl	%edi
+	movl	%edi, %eax
+	subl	%esi, %eax
+	ret
+
+it would be better to codegen as: x+~y  (notl+addl)
+
+//===---------------------------------------------------------------------===//