Souper says:

; Function: fn2
%0:i32 = var 
%1:i32 = subnsw 0:i32, %0
%2:i32 = and %0, %1
%3:i1 = eq 14:i32, %2
cand %3 0:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_147/foo.bc

LLVM says:

define void @fn2() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %sub.i = sub nsw i32 0, %0
  %and.i = and i32 %0, %sub.i
  %tobool.i = icmp eq i32 %and.i, 14
  br i1 %tobool.i, label %for.cond.i.preheader, label %for.cond1.preheader.split.i

for.cond.i.preheader:                             ; preds = %entry
  br label %for.cond.i

for.cond.i:                                       ; preds = %for.cond.i.preheader, %for.cond.i
  br label %for.cond.i

for.cond1.preheader.split.i:                      ; preds = %entry
  store i32 %and.i, i32* @b, align 4, !tbaa !1
  br label %for.cond1.i

for.cond1.i:                                      ; preds = %for.cond1.i, %for.cond1.preheader.split.i
  br label %for.cond1.i
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_147/foo.c -o reduce_147/foo.bc

C source code:

int a, b;
static unsigned char fn1();
void fn2() { fn1(14); }

unsigned char fn1(p1) {
  for (;;) {
    b = a & -a;
    if (p1 ^ b)
      for (;;)
        ;
  }
}

x86-64 from LLVM:

fn2:                                    # @fn2
	movl	a(%rip), %ecx
	movl	%ecx, %eax
	negl	%eax
	andl	%ecx, %eax
	cmpl	$14, %eax
	jne	.LBB0_2
.LBB0_1:                                # %for.cond.i
	jmp	.LBB0_1
.LBB0_2:                                # %for.cond1.preheader.split.i
	movl	%eax, b(%rip)
.LBB0_3:                                # %for.cond1.i
	jmp	.LBB0_3

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_147/foo.c -S -o -

x86-64 from GCC:

fn2:
	movl	a(%rip), %edx
	movl	%edx, %eax
	negl	%eax
	andl	%edx, %eax
	cmpl	$14, %eax
	jne	.L2
.L3:
	jmp	.L3
.L2:
	movl	%eax, b(%rip)
.L4:
	jmp	.L4

COMMAND: gcc -w -O3 reduce_147/foo.c -S -o -