#include "stdlib.h"

// this is an useful operation, it's a safe
// unsigned product with overflow-safety test
unsigned int mul(unsigned int a, unsigned int b) {
if ((unsigned long long)a * b > 0xffffffff)
    exit(1);
    return a * b;
}

/*
Args used to compile with gcc and llvm-gcc:
-Wall -O3 -fomit-frame-pointer -msse3 -march=native -S
On Windows
gcc: version 4.3.3-dw2-tdm-1 (GCC)
llvm-gcc: gcc version 4.2.1 (Based on Apple Inc. build 5636) (LLVM build)

----------------------------------

This is how the same thing may be done:

mov %esi, %eax
mul %edi
jo .L1
ret

----------------------------------

GCC:

_mul:
    subl    $28, %esp
    movl    %ebx, 16(%esp)
    movl    36(%esp), %ecx
    movl    32(%esp), %ebx
    movl    %ecx, %eax
    movl    %esi, 20(%esp)
    mull    %ebx
    movl    %edi, 24(%esp)
    cmpl    $0, %edx
    ja  L5
    imull   %ebx, %ecx
    movl    20(%esp), %esi
    movl    %ecx, %eax
    movl    16(%esp), %ebx
    movl    24(%esp), %edi
    addl    $28, %esp
    ret
L5:
    movl    $1, (%esp)
    call    _exit

-----------------------

LLVM-GCC:

_mul:
    pushl   %esi
    subl    $8, %esp
    movl    20(%esp), %ecx
    movl    16(%esp), %esi
    movl    %ecx, %eax
    mull    %esi
    testl   %edx, %edx
    jne LBB1_2  # bb
LBB1_1: # bb1
    movl    %ecx, %eax
    imull   %esi, %eax
    addl    $8, %esp
    popl    %esi
    ret
LBB1_2: # bb
    movl    $1, (%esp)
    call    _exit

*/