diff options
| -rw-r--r-- | lib/Target/X86/README.txt | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 846d69403f..60163e2193 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. + +//===---------------------------------------------------------------------===// |