Souper says:

; Function: fn1
%0:i32 = var 
%1:i32 = or 1:i32, %0
%2:i1 = sle %0, %1
cand %2 1:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_141/foo.bc

LLVM says:

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

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_141/foo.c -o reduce_141/foo.bc

C source code:

int a, b;
void fn1() {
  int c = (b | 0 == 0) >= b;
  a = c;
}

x86-64 from LLVM:

fn1:                                    # @fn1
	movl	b(%rip), %eax
	movl	%eax, %ecx
	orl	$1, %ecx
	cmpl	%eax, %ecx
	setge	%al
	movzbl	%al, %eax
	movl	%eax, a(%rip)
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_141/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	b(%rip), %eax
	movl	%eax, %edx
	orl	$1, %edx
	cmpl	%edx, %eax
	setle	%al
	movzbl	%al, %eax
	movl	%eax, a(%rip)
	ret

COMMAND: gcc -w -O3 reduce_141/foo.c -S -o -