Souper says:
; Function: fn1
%0:i32 = var
%1:i64 = sext %0
%2:i32 = lshr %0, 31:i32
%3:i32 = xor 1:i32, %2
%4:i64 = zext %3
%5:i64 = xor 4842753371:i64, %4
%6:i1 = sle %1, %5
cand %6 1:i1
COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_795/foo.bc
LLVM says:
define void @fn1() #0 {
entry:
%0 = load i32* @b, align 4, !tbaa !1
%.lobit = lshr i32 %0, 31
%.lobit.not = xor i32 %.lobit, 1
%conv15 = zext i32 %.lobit.not to i64
%xor = xor i64 %conv15, 4842753371
%conv2 = sext i32 %0 to i64
%cmp3 = icmp sge i64 %xor, %conv2
%conv4 = zext i1 %cmp3 to i32
store i32 %conv4, i32* @a, align 4, !tbaa !1
ret void
}
COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_795/foo.c -o reduce_795/foo.bc
C source code:
int a, b;
void fn1() { a = (0 <= b ^ 4842753371) >= b; }
x86-64 from LLVM:
fn1: # @fn1
movslq b(%rip), %rax
movl %eax, %ecx
shrl $31, %ecx
xorl $1, %ecx
movabsq $4842753371, %rdx # imm = 0x120A68D5B
xorq %rcx, %rdx
cmpq %rax, %rdx
setge %al
movzbl %al, %eax
movl %eax, a(%rip)
retq
COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_795/foo.c -S -o -
x86-64 from GCC:
fn1:
movl $1, a(%rip)
ret
COMMAND: gcc -w -O3 reduce_795/foo.c -S -o -