Souper says:

; Function: fn1
%0:i32 = var 
%1:i64 = sext %0
%2:i64 = sdiv 21474836471:i64, %1
%3:i1 = ne 0:i64, %2
cand %3 1:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_296/foo.bc

LLVM says:

define i32 @fn1() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %conv = sext i32 %0 to i64
  %div = sdiv i64 21474836471, %conv
  %tobool = icmp ne i64 %div, 0
  %lor.ext = zext i1 %tobool to i32
  ret i32 %lor.ext
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_296/foo.c -o reduce_296/foo.bc

C source code:

int a;
int fn1() { return 21474836471 / a || 0; }

x86-64 from LLVM:

fn1:                                    # @fn1
	movslq	a(%rip), %rcx
	movabsq	$21474836471, %rax      # imm = 0x4FFFFFFF7
	xorl	%edx, %edx
	idivq	%rcx
	testq	%rax, %rax
	setne	%al
	movzbl	%al, %eax
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_296/foo.c -S -o -

x86-64 from GCC:

fn1:
	movslq	a(%rip), %rcx
	movabsq	$21474836471, %rax
	cqto
	idivq	%rcx
	testq	%rax, %rax
	setne	%al
	movzbl	%al, %eax
	ret

COMMAND: gcc -w -O3 reduce_296/foo.c -S -o -