Author: lattner
Date: Fri Nov 2 12:04:20 2007
New Revision: 43642
URL: http://llvm.org/viewvc/llvm-project?rev=43642&view=rev
Log:
add a note
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=43642&r1=43641&r2=43642&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Fri Nov 2 12:04:20 2007
@@ -651,6 +651,26 @@
etc.
+Another is:
+int usesbb(unsigned int a, unsigned int b) {
+ return (a < b ? -1 : 0);
+}
+to:
+_usesbb:
+ movl 8(%esp), %eax
+ cmpl %eax, 4(%esp)
+ sbbl %eax, %eax
+ ret
+
+instead of:
+_usesbb:
+ xorl %eax, %eax
+ movl 8(%esp), %ecx
+ cmpl %ecx, 4(%esp)
+ movl $4294967295, %ecx
+ cmovb %ecx, %eax
+ ret
+
//===---------------------------------------------------------------------===//
Currently we don't have elimination of redundant stack manipulations. Consider
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