Souper says:

; Function: main
%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_97/foo.bc

LLVM says:

define i32 @fn1() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %tobool = icmp ne i32 %0, 0
  %. = select i1 %tobool, i32 %0, i32 1
  ret i32 %.
}
define i32 @main() #1 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %tobool.i = icmp ne i32 %0, 0
  %..i = select i1 %tobool.i, i32 %0, i32 1
  %tobool = icmp eq i32 %..i, 0
  br i1 %tobool, label %for.cond.preheader, label %for.cond1.preheader.split

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

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

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

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

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_97/foo.c -o reduce_97/foo.bc

C source code:

int a, b;
int fn1() { return a ?: 1; }

int main() {
  for (;;) {
    b = fn1();
    if (b)
      for (;;)
        ;
  }
}

x86-64 from LLVM:

fn1:                                    # @fn1
	movl	a(%rip), %ecx
	testl	%ecx, %ecx
	movl	$1, %eax
	cmovnel	%ecx, %eax
	retq
main:                                   # @main
	movl	a(%rip), %ecx
	testl	%ecx, %ecx
	movl	$1, %eax
	cmovnel	%ecx, %eax
	testl	%eax, %eax
	je	.LBB1_1
	movl	%eax, b(%rip)
.LBB1_3:                                # %for.cond1
	jmp	.LBB1_3
.LBB1_1:                                # %for.cond
	jmp	.LBB1_1
.Ltmp1:

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_97/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	a(%rip), %edx
	movl	$1, %eax
	testl	%edx, %edx
	cmovne	%edx, %eax
	ret
main:
.LFB1:
	movl	a(%rip), %edx
	movl	$1, %eax
	testl	%edx, %edx
	cmovne	%edx, %eax
	movl	%eax, b(%rip)
.L6:
	jmp	.L6
.LFE1:

COMMAND: gcc -w -O3 reduce_97/foo.c -S -o -