Souper says:

; Function: fn1
%0:i32 = var 
%1:i1 = slt %0, 0:i32
pc %1 1:i1
%2:i32 = subnsw 1:i32, %0
%3:i1 = slt 0:i32, %2
cand %3 1:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_354/foo.bc

LLVM says:

define i32 @fn1() #0 {
entry:
  %0 = load i32* @a, align 4, !tbaa !1
  %cmp = icmp slt i32 %0, 0
  br i1 %cmp, label %land.rhs, label %land.end

land.rhs:                                         ; preds = %entry
  %sub = sub nsw i32 1, %0
  %cmp1 = icmp sgt i32 %sub, 0
  br label %land.end

land.end:                                         ; preds = %land.rhs, %entry
  %1 = phi i1 [ false, %entry ], [ %cmp1, %land.rhs ]
  %land.ext = zext i1 %1 to i32
  ret i32 %land.ext
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_354/foo.c -o reduce_354/foo.bc

C source code:

int a;
int fn1() { return a < 0 && 0 < 1 - a; }

x86-64 from LLVM:

fn1:                                    # @fn1
	movl	a(%rip), %eax
	testl	%eax, %eax
	js	.LBB0_2
	xorl	%eax, %eax
	movzbl	%al, %eax
	retq
.LBB0_2:                                # %land.rhs
	movl	$1, %ecx
	subl	%eax, %ecx
	testl	%ecx, %ecx
	setg	%al
	movzbl	%al, %eax
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_354/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	a(%rip), %eax
	shrl	$31, %eax
	ret

COMMAND: gcc -w -O3 reduce_354/foo.c -S -o -