According to i386 System V ABI:
1. when __m256 are required to be passed on the stack, the stack pointer must be aligned on a 0 mod 32 byte boundary at the time of the call.
2. when __m512 are required to be passed on the stack, the stack pointer must be aligned on a 0 mod 64 byte boundary at the time of the call.
The current method of clang passing __m512 parameter are as follow:
1. when target supports avx512, passing it with 64 byte alignment;
2. when target supports avx, passing it with 32 byte alignment;
3. Otherwise, passing it with 16 byte alignment.
Passing __m256 parameter are as follow:
1. when target supports avx or avx512, passing it with 32 byte alignment;
2. Otherwise, passing it with 16 byte alignment.
This pach will passing __m128/__m256/__m512 following i386 System V ABI and
apply it to Linux only since other System V OS (e.g Darwin, PS4 and FreeBSD) don't
want to spend any effort dealing with the ramifications of ABI breaks at present.
Differential Revision: https://reviews.llvm.org/D78564
According to i386 System V ABI 2.1: Structures and unions assume the
alignment of their most strictly aligned component. But current
implementation always takes them as 4-byte aligned which will result
in incorrect code, e.g:
1 #include <immintrin.h>
2 typedef union {
3 int d[4];
4 __m128 m;
5 } M128;
6 extern void foo(int, ...);
7 void test(void)
8 {
9 M128 a;
10 foo(1, a);
11 foo(1, a.m);
12 }
The first call (line 10) takes the second arg as 4-byte aligned while
the second call (line 11) takes the second arg as 16-byte aligned.
There is oxymoron for the alignment of the 2 calls because they should
be the same.
This patch fixes the bug by following i386 System V ABI and apply it to
Linux only since other System V OS (e.g Darwin, PS4 and FreeBSD) don't
want to spend any effort dealing with the ramifications of ABI breaks
at present.
Patch by Wei Xiao (wxiao3)
Differential Revision: https://reviews.llvm.org/D60748
llvm-svn: 361934
Liu, Chen3