Souper says:

; Function: fn1
%0:i32 = var 
%1:i64 = sext %0
%2:i64 = and 9223372036854775808:i64, %1
%3:i64 = addnsw 18446744073709551611:i64, %2
%4:i1 = slt %3, 0:i64
cand %4 1:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_165/foo.bc

LLVM says:

define void @fn1() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %conv = sext i32 %0 to i64
  %and = and i64 %conv, -9223372036854775808
  %sub = add nsw i64 %and, -5
  %cmp = icmp slt i64 %sub, 0
  %sub.lobit = lshr i64 %sub, 63
  %1 = trunc i64 %sub.lobit to i32
  %conv1. = select i1 %cmp, i32 %1, i32 0
  store i32 %conv1., i32* @b, align 4, !tbaa !1
  ret void
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_165/foo.c -o reduce_165/foo.bc

C source code:

int a, b;
void fn1() { b = (a & ~9223372036854775807LL) - 5 < 0 ?: 0; }

x86-64 from LLVM:

fn1:                                    # @fn1
	movslq	a(%rip), %rax
	movabsq	$-9223372036854775808, %rcx # imm = 0x8000000000000000
	andq	%rax, %rcx
	addq	$-5, %rcx
	shrq	$63, %rcx
	andl	%ecx, %ecx
	movl	%ecx, b(%rip)
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_165/foo.c -S -o -

x86-64 from GCC:

fn1:
	movslq	a(%rip), %rax
	movabsq	$-9223372036854775808, %rdx
	andq	%rdx, %rax
	cmpq	$4, %rax
	setle	%al
	movzbl	%al, %eax
	movl	%eax, b(%rip)
	ret

COMMAND: gcc -w -O3 reduce_165/foo.c -S -o -