Souper says:

; Function: fn1
%0:i32 = var 
%1:i32 = var 
%2:i32 = xor %0, %1
%3:i32 = xor 2147483648:i32, %0, %1
%4:i32 = and %2, %3
%5:i1 = slt %4, 0:i32
cand %5 0:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_602/foo.bc

LLVM says:

define void @fn1() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %1 = load i32* @b, align 4, !tbaa !1
  %xor = xor i32 %1, %0
  %neg = xor i32 %0, -2147483648
  %xor1 = xor i32 %neg, %1
  %and = and i32 %xor, %xor1
  %cmp = icmp slt i32 %and, 0
  %and.lobit = lshr i32 %and, 31
  %conv. = select i1 %cmp, i32 %and.lobit, i32 0
  store i32 %conv., i32* @c, align 4, !tbaa !1
  ret void
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_602/foo.c -o reduce_602/foo.bc

C source code:

int a, b, c;
void fn1() { c = ((a ^ b) & (a ^ ~b)) < 0 ?: 0; }

x86-64 from LLVM:

fn1:                                    # @fn1
	movl	b(%rip), %eax
	xorl	a(%rip), %eax
	movl	%eax, %ecx
	notl	%ecx
	andl	%eax, %eax
	andl	%ecx, %eax
	shrl	$31, %eax
	movl	%eax, c(%rip)
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_602/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	b(%rip), %ecx
	movl	a(%rip), %edx
	movl	%ecx, %eax
	notl	%eax
	xorl	%edx, %eax
	xorl	%ecx, %edx
	andl	%edx, %eax
	shrl	$31, %eax
	movl	%eax, c(%rip)
	ret

COMMAND: gcc -w -O3 reduce_602/foo.c -S -o -