Souper says:
; Function: fn2
%0:i8 = var
%1:i32 = sext %0
%2:i32 = addnsw 4294966725:i32, %1
%3:i1 = slt %2, 0:i32
cand %3 1:i1
COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_549/foo.bc
LLVM says:
define i32 @fn1(i32 %p1) #0 {
entry:
%cmp = icmp slt i32 %p1, 0
%p1.lobit = lshr i32 %p1, 31
%conv. = select i1 %cmp, i32 %p1.lobit, i32 0
ret i32 %conv.
}
define void @fn2() #1 {
entry:
%0 = load i8* @a, align 1, !tbaa !1
%conv = sext i8 %0 to i32
%sub = add nsw i32 %conv, -571
%cmp.i = icmp slt i32 %sub, 0
%p1.lobit.i = lshr i32 %sub, 31
%conv..i = select i1 %cmp.i, i32 %p1.lobit.i, i32 0
store i32 %conv..i, i32* @b, align 4, !tbaa !4
ret void
}
COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_549/foo.c -o reduce_549/foo.bc
C source code:
char a;
int b;
int fn1(p1) { return p1 < 0 ?: 0; }
void fn2() { b = fn1(a - 571); }
x86-64 from LLVM:
fn1: # @fn1
andl %edi, %edi
shrl $31, %edi
movl %edi, %eax
retq
fn2: # @fn2
movsbl a(%rip), %eax
addl $-571, %eax # imm = 0xFFFFFFFFFFFFFDC5
andl %eax, %eax
shrl $31, %eax
movl %eax, b(%rip)
retq
.Ltmp1:
COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_549/foo.c -S -o -
x86-64 from GCC:
fn1:
movl %edi, %eax
shrl $31, %eax
ret
fn2:
.LFB1:
movl $1, b(%rip)
ret
.LFE1:
COMMAND: gcc -w -O3 reduce_549/foo.c -S -o -