Souper says:

; Function: fn1
%0:i8 = var 
%1:i32 = sext %0
%2:i32 = or 1:i32, %1
%3:i1 = eq 217:i32, %2
cand %3 0:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_157/foo.bc

LLVM says:

define void @fn1(i32 %p1) #0 {
entry:
  %xor1 = or i32 %p1, 1
  %cmp2 = icmp eq i32 %xor1, 217
  br i1 %cmp2, label %if.then, label %if.end.lr.ph

if.end.lr.ph:                                     ; preds = %entry
  %0 = load i8* @a, align 1, !tbaa !1
  %conv = sext i8 %0 to i32
  %xor = or i32 %conv, 1
  %cmp = icmp eq i32 %xor, 217
  br i1 %cmp, label %if.then, label %if.end.preheader

if.end.preheader:                                 ; preds = %if.end.lr.ph
  br label %if.end

if.then:                                          ; preds = %if.end.lr.ph, %entry
  store i8 0, i8* @a, align 1, !tbaa !1
  br label %for.cond

for.cond:                                         ; preds = %for.cond, %if.then
  br label %for.cond

if.end:                                           ; preds = %if.end.preheader, %if.end
  br label %if.end
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_157/foo.c -o reduce_157/foo.bc

C source code:

char a;
void fn1(p1) {
  if ((1 | p1 ^ 216) == 1) {
    a = 0;
    for (;;)
      ;
  }
  fn1(a);
}

x86-64 from LLVM:

fn1:                                    # @fn1
	orl	$1, %edi
	cmpl	$217, %edi
	je	.LBB0_2
	movsbl	a(%rip), %eax
	orl	$1, %eax
	cmpl	$217, %eax
	jne	.LBB0_4
.LBB0_2:                                # %if.then
	movb	$0, a(%rip)
.LBB0_3:                                # %for.cond
	jmp	.LBB0_3
.LBB0_4:                                # %if.end
	jmp	.LBB0_4

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_157/foo.c -S -o -

x86-64 from GCC:

fn1:
	xorb	$-40, %dil
	orl	$1, %edi
	cmpl	$1, %edi
	je	.L4
	movsbl	a(%rip), %eax
	xorb	$-40, %al
	orl	$1, %eax
	cmpl	$1, %eax
	je	.L4
.L5:
	jmp	.L5
.L4:
	movb	$0, a(%rip)
.L3:
	jmp	.L3

COMMAND: gcc -w -O3 reduce_157/foo.c -S -o -