[llvm-commits] [llvm] r47237 - /llvm/trunk/lib/Target/X86/README.txt

[Chris Lattner]

Author: lattner
Date: Sun Feb 17 13:43:57 2008
New Revision: 47237

URL: http://llvm.org/viewvc/llvm-project?rev=47237&view=rev
Log:
move PR2053 to here.

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=47237&r1=47236&r2=47237&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Sun Feb 17 13:43:57 2008
@@ -1516,3 +1516,15 @@
 lock ; mov %esp, %esp
 
 //===---------------------------------------------------------------------===//
+
+The generated code on x86 for checking for signed overflow on a multiply the
+obvious way is much longer than it needs to be.
+
+int x(int a, int b) {
+  long long prod = (long long)a*b;
+  return  prod > 0x7FFFFFFF || prod < (-0x7FFFFFFF-1);
+}
+
+See PR2053 for more details.
+
+//===---------------------------------------------------------------------===//