From 456012c72e8596e36596ab3798b1d271477955ef Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Sun, 17 Feb 2008 19:43:57 +0000 Subject: [PATCH] move PR2053 to here. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47237 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Target/X86/README.txt | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 846d69403f1..60163e21934 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -1516,3 +1516,15 @@ should generate: 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. + +//===---------------------------------------------------------------------===//