Souper says:
; Function: fn1
%0:i32 = var
%1:i1 = eq 0:i32, %0
pc %1 1:i1
%2:i32 = addnsw 1:i32, %0
%3:i1 = slt %2, 6:i32
cand %3 1:i1
COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_75/foo.bc
LLVM says:
define void @fn1() #0 {
entry:
store i32 0, i32* @a, align 4, !tbaa !1
%b.promoted = load i32* @b, align 4, !tbaa !1
br label %for.body
for.cond: ; preds = %for.body
store i32 %inc, i32* @a, align 4, !tbaa !1
%cmp = icmp slt i32 %inc, 6
br i1 %cmp, label %for.body, label %lbl_16
for.body: ; preds = %entry, %for.cond
%0 = phi i32 [ 0, %entry ], [ %inc, %for.cond ]
%dec1 = phi i32 [ %b.promoted, %entry ], [ %dec, %for.cond ]
%dec = add nsw i32 %dec1, -1
%tobool = icmp eq i32 %0, 0
%inc = add nsw i32 %0, 1
br i1 %tobool, label %for.cond, label %lbl_16
lbl_16: ; preds = %for.body, %for.cond
%dec.lcssa = phi i32 [ %dec, %for.body ], [ %dec, %for.cond ]
store i32 %dec.lcssa, i32* @b, align 4, !tbaa !1
ret void
}
COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_75/foo.c -o reduce_75/foo.bc
C source code:
int a, b;
void fn1() {
a = 0;
for (; a <= 5; a++) {
--b;
if (a)
goto lbl_16;
}
lbl_16:
;
}
x86-64 from LLVM:
fn1: # @fn1
movl $0, a(%rip)
movl b(%rip), %edx
decl %edx
xorl %eax, %eax
.LBB0_2: # %for.body
movl %edx, %ecx
testl %eax, %eax
jne .LBB0_3
incl %eax
movl %eax, a(%rip)
leal -1(%rcx), %edx
cmpl $5, %eax
jle .LBB0_2
.LBB0_3: # %lbl_16
movl %ecx, b(%rip)
retq
COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_75/foo.c -S -o -
x86-64 from GCC:
fn1:
movl b(%rip), %eax
movl $1, a(%rip)
subl $2, %eax
movl %eax, b(%rip)
ret
COMMAND: gcc -w -O3 reduce_75/foo.c -S -o -