[Bug target/116043] [15 regression] TLS relocation issue when building glibc with -O3 -mavx512bf16 by r15-1619

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116043

--- Comment #16 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by hongtao Liu <liuhongt@gcc.gnu.org>:

https://gcc.gnu.org/g:bc1fda00d5f20e2f3e77a50b2822562b6e0040b2

commit r15-2395-gbc1fda00d5f20e2f3e77a50b2822562b6e0040b2
Author: liuhongt <hongtao.liu@intel.com>
Date:   Wed Jul 24 11:29:23 2024 +0800

    Refine constraint "Bk" to define_special_memory_constraint.

    For below pattern, RA may still allocate r162 as v/k register, try to
    reload for address with leaq __libc_tsd_CTYPE_B@gottpoff(%rip), %rsi
    which result a linker error.

    (set (reg:DI 162)
         (mem/u/c:DI
           (const:DI (unspec:DI
                     [(symbol_ref:DI ("a") [flags 0x60]  <var_decl
0x7f621f6e1c60 a>)]
                     UNSPEC_GOTNTPOFF))

    Quote from H.J for why linker issue an error.
    >What do these do:
    >
    >        leaq    __libc_tsd_CTYPE_B@gottpoff(%rip), %rax
    >        vmovq   (%rax), %xmm0
    >
    >From x86-64 TLS psABI:
    >
    >The assembler generates for the x@gottpoff(%rip) expressions a R X86
    >64 GOTTPOFF relocation for the symbol x which requests the linker to
    >generate a GOT entry with a R X86 64 TPOFF64 relocation. The offset of
    >the GOT entry relative to the end of the instruction is then used in
    >the instruction. The R X86 64 TPOFF64 relocation is pro- cessed at
    >program startup time by the dynamic linker by looking up the symbol x
    >in the modules loaded at that point. The offset is written in the GOT
    >entry and later loaded by the addq instruction.
    >
    >The above code sequence looks wrong to me.

    gcc/ChangeLog:

            PR target/116043
            * config/i386/constraints.md (Bk): Refine to
            define_special_memory_constraint.

    gcc/testsuite/ChangeLog:

            * gcc.target/i386/pr116043.c: New test.