For a default visibility external linkage definition, dso_local is set for ELF
-fno-pic/-fpie and COFF and Mach-O. Since default clang -cc1 for ELF is similar
to -fpic ("PIC Level" is not set), this nuance causes unneeded binary format differences.
To make emitted IR similar, ELF -cc1 -fpic will default to -fno-semantic-interposition,
which sets dso_local for default visibility external linkage definitions.
To make this flip smooth and enable future (dso_local as definition default),
this patch replaces (function) `define ` with `define{{.*}} `,
(variable/constant/alias) `= ` with `={{.*}} `, or inserts appropriate `{{.*}} `.
Recently commit D78699 (commit 26cfb6e562), fixed clang's behavior with respect
to passing a union type through a register to correctly follow the ABI. However,
this is an ABI breaking change with earlier versions of the clang compiler, so we
should add an -fclang-abi-compat option to address this. Additionally, the PS4 ABI
requires the older behavior, so that is added as well.
This change adds a Ver11 value to the ClangABI enum that when it is set (or the
target is the PS4 triple), we skip the ABI fix introduced in D78699.
Differential Revision: https://reviews.llvm.org/D89747
For example:
union M256 {
double d;
__m256 m;
};
extern void foo1(union M256 A);
union M256 m1;
void test() {
foo1(m1);
}
clang will pass m1 through stack which does not follow the ABI.
Differential Revision: https://reviews.llvm.org/D78699
Fangrui Song