Souper says:

; Function: fn1
%0:i8 = var 
%1:i1 = eq 0:i8, %0
%2:i32 = var 
%3:i1 = eq 0:i32, %2
%4:i1 = or %1, %3
pc %4 1:i1
%5:i1 = xor 1:i1, %3
%6:i1 = ne 0:i8, %0
%7:i1 = and %5, %6
cand %7 0:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_77/foo.bc

LLVM says:

define i32 @fn1() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %tobool = icmp eq i32 %0, 0
  %1 = load i8* @b, align 1
  %tobool1 = icmp eq i8 %1, 0
  %or.cond = or i1 %tobool, %tobool1
  br i1 %or.cond, label %lor.rhs, label %lor.end

lor.rhs:                                          ; preds = %entry
  %tobool4 = icmp ne i8 %1, 0
  %not.tobool = xor i1 %tobool, true
  %.tobool4 = and i1 %tobool4, %not.tobool
  br label %lor.end

lor.end:                                          ; preds = %lor.rhs, %entry
  %2 = phi i1 [ true, %entry ], [ %.tobool4, %lor.rhs ]
  %lor.ext = zext i1 %2 to i32
  ret i32 %lor.ext
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_77/foo.c -o reduce_77/foo.bc

C source code:

int a;
char b;
int fn1() { return a && b || a && b; }

x86-64 from LLVM:

fn1:                                    # @fn1
	movl	a(%rip), %eax
	testl	%eax, %eax
	movb	b(%rip), %dl
	je	.LBB0_2
	movb	$1, %cl
	testb	%dl, %dl
	jne	.LBB0_3
.LBB0_2:                                # %lor.rhs
	testb	%dl, %dl
	setne	%dl
	testl	%eax, %eax
	setne	%cl
	andb	%dl, %cl
.LBB0_3:                                # %lor.end
	movzbl	%cl, %eax
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_77/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	a(%rip), %edx
	xorl	%eax, %eax
	testl	%edx, %edx
	je	.L2
	xorl	%eax, %eax
	cmpb	$0, b(%rip)
	setne	%al
.L2:
	rep ret

COMMAND: gcc -w -O3 reduce_77/foo.c -S -o -