Souper says:

; Function: fn1
%0:i32 = var 
%1:i1 = slt %0, 1:i32
%2:i32 = zext %1
%3:i1 = eq %0, %2
cand %3 0:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_138/foo.bc

LLVM says:

define void @fn1() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %cmp = icmp slt i32 %0, 1
  %conv = zext i1 %cmp to i32
  %cmp1 = icmp eq i32 %conv, %0
  %conv2 = zext i1 %cmp1 to i32
  store i32 %conv2, i32* @c, align 4, !tbaa !1
  ret void
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_138/foo.c -o reduce_138/foo.bc

C source code:

int a, c;
static int *b = &a;
void fn1() {
  int d = *b;
  c = 0 >= a == d;
}

x86-64 from LLVM:

fn1:                                    # @fn1
	movl	a(%rip), %eax
	testl	%eax, %eax
	setle	%cl
	movzbl	%cl, %ecx
	cmpl	%eax, %ecx
	sete	%al
	movzbl	%al, %eax
	movl	%eax, c(%rip)
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_138/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	a(%rip), %eax
	xorl	%edx, %edx
	testl	%eax, %eax
	setle	%dl
	cmpl	%eax, %edx
	sete	%al
	movzbl	%al, %eax
	movl	%eax, c(%rip)
	ret

COMMAND: gcc -w -O3 reduce_138/foo.c -S -o -