Souper says:

; Function: fn1
%0:i32 = var 
%1:i1 = eq 0:i32, %0
pc %1 1:i1
%2:i32 = addnsw 4294967295:i32, %0
%3:i16 = var 
%4:i32 = zext %3
%5:i1 = eq %2, %4
cand %5 0:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_164/foo.bc

LLVM says:

define void @fn1() #0 {
entry:
  %0 = load i32* @b, align 4, !tbaa !1
  %sub = add nsw i32 %0, -1
  store i32 %sub, i32* @a, align 4, !tbaa !1
  %tobool = icmp eq i32 %0, 0
  br i1 %tobool, label %if.else, label %if.end3

if.else:                                          ; preds = %entry
  %1 = load i16* @c, align 2, !tbaa !5
  %conv = zext i16 %1 to i32
  %cmp = icmp eq i32 %sub, %conv
  br i1 %cmp, label %if.end3, label %for.cond.preheader

for.cond.preheader:                               ; preds = %if.else
  br label %for.cond

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

if.end3:                                          ; preds = %if.else, %entry
  ret void
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_164/foo.c -o reduce_164/foo.bc

C source code:

int a, b;
unsigned short c;
void fn1() {
  int *d = &a;
  *d = b - 1;
  if (b)
    ;
  else if (*d != c)
    for (;;)
      ;
}

x86-64 from LLVM:

fn1:                                    # @fn1
	movl	b(%rip), %ecx
	leal	-1(%rcx), %eax
	testl	%ecx, %ecx
	movl	%eax, a(%rip)
	jne	.LBB0_3
	movzwl	c(%rip), %ecx
	cmpl	%ecx, %eax
	jne	.LBB0_2
.LBB0_3:                                # %if.end3
	retq
.LBB0_2:                                # %for.cond
	jmp	.LBB0_2

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_164/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	b(%rip), %eax
	leal	-1(%rax), %edx
	testl	%eax, %eax
	movl	%edx, a(%rip)
	jne	.L1
.L3:
	jmp	.L3
.L1:
	rep ret

COMMAND: gcc -w -O3 reduce_164/foo.c -S -o -