Souper says:

; Function: fn1
%0:i32 = var 
%1:i32 = var 
%2:i32 = mul %0, %1
%3:i1 = eq 0:i32, %2
pc %3 0:i1
%4:i1 = eq 0:i32, %0
cand %4 0:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_397/foo.bc

LLVM says:

define void @fn1() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %1 = load i32* @b, align 4, !tbaa !1
  %mul = mul nsw i32 %1, %0
  store i32 %mul, i32* @c, align 4, !tbaa !1
  %tobool = icmp eq i32 %mul, 0
  br i1 %tobool, label %if.end4, label %for.cond.preheader

for.cond.preheader:                               ; preds = %entry
  %phitmp = icmp eq i32 %1, 0
  br label %for.cond

for.cond:                                         ; preds = %for.cond.preheader, %for.cond
  %2 = phi i1 [ true, %for.cond ], [ %phitmp, %for.cond.preheader ]
  br i1 %2, label %for.cond, label %for.cond3.preheader

for.cond3.preheader:                              ; preds = %for.cond
  br label %for.cond3

for.cond3:                                        ; preds = %for.cond3.preheader, %for.cond3
  br label %for.cond3

if.end4:                                          ; preds = %entry
  ret void
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_397/foo.c -o reduce_397/foo.bc

C source code:

int a, b, c;
void fn1() {
  c = a * b;
  if (c)
    for (;;)
      if (b)
        for (;;)
          ;
}

x86-64 from LLVM:

fn1:                                    # @fn1
	movl	b(%rip), %eax
	movl	a(%rip), %ecx
	imull	%eax, %ecx
	testl	%ecx, %ecx
	movl	%ecx, c(%rip)
	je	.LBB0_4
	testl	%eax, %eax
	sete	%al
.LBB0_2:                                # %for.cond
	testb	$1, %al
	movb	$1, %al
	jne	.LBB0_2
.LBB0_3:                                # %for.cond3
	jmp	.LBB0_3
.LBB0_4:                                # %if.end4
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_397/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	b(%rip), %eax
	movl	a(%rip), %edx
	imull	%eax, %edx
	testl	%edx, %edx
	movl	%edx, c(%rip)
	je	.L1
	testl	%eax, %eax
	jne	.L4
.L6:
	jmp	.L6
.L4:
	jmp	.L4
.L1:
	rep ret

COMMAND: gcc -w -O3 reduce_397/foo.c -S -o -