#define NULL ((void *)0)
typedef unsigned long size_t; // Customize by platform.
typedef long intptr_t;
typedef unsigned long uintptr_t;
typedef long scalar_t__; // Either arithmetic or pointer type.
/* By default, we understand bool (as a convenience). */
typedef int bool;
#define false 0
#define true 1

/* Forward declarations */

/* Type definitions */
struct timeval {
  int tv_sec;
  int tv_usec;
};

/* Variables and functions */
float timediff(struct timeval *begin, struct timeval *end) {
  int n;
  n = (end->tv_sec - begin->tv_sec) * 1000000 + (end->tv_usec - begin->tv_usec);
  return (float)(n / 1000);
}


x86 assembly (clang, -O0):
<timediff>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    -0x10(%rbp),%rax
mov    (%rax),%eax
mov    -0x8(%rbp),%rcx
sub    (%rcx),%eax
imul   $0xf4240,%eax,%eax
mov    -0x10(%rbp),%rcx
mov    0x4(%rcx),%ecx
mov    -0x8(%rbp),%rdx
sub    0x4(%rdx),%ecx
add    %ecx,%eax
mov    %eax,-0x14(%rbp)
mov    -0x14(%rbp),%eax
mov    $0x3e8,%ecx
cltd
idiv   %ecx
cvtsi2ss %eax,%xmm0
pop    %rbp
ret

x86 assembly (clang, -O2):
<timediff>:
mov    (%rsi),%eax
mov    0x4(%rsi),%ecx
sub    (%rdi),%eax
imul   $0xf4240,%eax,%eax
sub    0x4(%rdi),%ecx
add    %eax,%ecx
movslq %ecx,%rax
imul   $0x10624dd3,%rax,%rax
mov    %rax,%rcx
shr    $0x3f,%rcx
sar    $0x26,%rax
add    %ecx,%eax
cvtsi2ss %eax,%xmm0
ret

LLVM IR (-O0):
%struct.timeval = type { i32, i32 }
define float @timediff(%struct.timeval* %0, %struct.timeval* %1) {
%3 = alloca %struct.timeval*
%4 = alloca %struct.timeval*
%5 = alloca i32
store %struct.timeval* %0, %struct.timeval** %3
store %struct.timeval* %1, %struct.timeval** %4
%6 = load %struct.timeval*, %struct.timeval** %4
%7 = getelementptr inbounds %struct.timeval, %struct.timeval* %6, i32 0, i32 0
%8 = load i32, i32* %7
%9 = load %struct.timeval*, %struct.timeval** %3
%10 = getelementptr inbounds %struct.timeval, %struct.timeval* %9, i32 0, i32 0
%11 = load i32, i32* %10
%12 = sub nsw i32 %8, %11
%13 = mul nsw i32 %12, 1000000
%14 = load %struct.timeval*, %struct.timeval** %4
%15 = getelementptr inbounds %struct.timeval, %struct.timeval* %14, i32 0, i32 1
%16 = load i32, i32* %15
%17 = load %struct.timeval*, %struct.timeval** %3
%18 = getelementptr inbounds %struct.timeval, %struct.timeval* %17, i32 0, i32 1
%19 = load i32, i32* %18
%20 = sub nsw i32 %16, %19
%21 = add nsw i32 %13, %20
store i32 %21, i32* %5
%22 = load i32, i32* %5
%23 = sdiv i32 %22, 1000
%24 = sitofp i32 %23 to float
ret float %24
}

LLVM IR (-O2):
%struct.timeval = type { i32, i32 }
define float @timediff(%struct.timeval* nocapture %0, %struct.timeval* nocapture %1) {
%3 = getelementptr inbounds %struct.timeval, %struct.timeval* %1, i64 0, i32 0
%4 = load i32, i32* %3
%5 = getelementptr inbounds %struct.timeval, %struct.timeval* %0, i64 0, i32 0
%6 = load i32, i32* %5
%7 = sub nsw i32 %4, %6
%8 = mul nsw i32 %7, 1000000
%9 = getelementptr inbounds %struct.timeval, %struct.timeval* %1, i64 0, i32 1
%10 = load i32, i32* %9
%11 = getelementptr inbounds %struct.timeval, %struct.timeval* %0, i64 0, i32 1
%12 = load i32, i32* %11
%13 = sub i32 %10, %12
%14 = add nsw i32 %13, %8
%15 = sdiv i32 %14, 1000
%16 = sitofp i32 %15 to float
ret float %16
}