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.
+
+//===---------------------------------------------------------------------===//
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