Souper says:

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

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_198/foo.bc

LLVM says:

define void @fn1() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %tobool = icmp ne i32 %0, 0
  %. = select i1 %tobool, i32 %0, i32 1
  store i32 %., i32* @b, align 4, !tbaa !1
  %tobool1 = icmp eq i32 %., 0
  br i1 %tobool1, label %for.end.split, label %for.cond.preheader

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

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

for.end.split:                                    ; preds = %entry
  ret void
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_198/foo.c -o reduce_198/foo.bc

C source code:

int a, b;
void fn1() {
  b = a ?: 1;
  for (; b;)
    ;
}

x86-64 from LLVM:

fn1:                                    # @fn1
	movl	a(%rip), %eax
	testl	%eax, %eax
	movl	$1, %ecx
	cmovnel	%eax, %ecx
	testl	%ecx, %ecx
	movl	%ecx, b(%rip)
	je	.LBB0_2
.LBB0_1:                                # %for.cond
	jmp	.LBB0_1
.LBB0_2:                                # %for.end.split
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_198/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	a(%rip), %edx
	movl	$1, %eax
	testl	%edx, %edx
	cmovne	%edx, %eax
	movl	%eax, b(%rip)
.L3:
	jmp	.L3

COMMAND: gcc -w -O3 reduce_198/foo.c -S -o -