https://bugs.llvm.org/show_bug.cgi?id=46724
Bug ID: 46724
Summary: Failure to use x86 array arithmetic instead of manual
add
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: gabrav...@gmail.com
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
llvm-...@redking.me.uk, spatel+l...@rotateright.com
struct as
{
as* a;
as* b;
};
struct b
{
as* a;
as* b;
};
void f(b* a, as* s)
{
if (a->a)
{
s->a = a->a;
a->a->b = s;
}
else
{
a->b = s;
}
}
With -O3, GCC outputs this :
f(b*, as*):
mov rax, QWORD PTR [rdi]
test rax, rax
je .L2
mov QWORD PTR [rsi], rax
mov QWORD PTR [rax+8], rsi
ret
.L2:
mov QWORD PTR [rdi+8], rsi
ret
LLVM outputs this :
f(b*, as*): # @f(b*, as*)
mov rax, qword ptr [rdi]
test rax, rax
je .LBB0_2
mov qword ptr [rsi], rax
add rax, 8
mov qword ptr [rax], rsi
ret
.LBB0_2:
add rdi, 8
mov qword ptr [rdi], rsi
ret
--
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