On Mon, Aug 04, 2025 at 02:57:39PM +0800, Hongtao Liu wrote:
> > > > > + rtx_insn *before = nullptr;
> > > > > + rtx_insn *after = nullptr;
> > > > > + if (insn == BB_HEAD (bb))
> > > > > + before = insn;
> > > > > + else
> > > > > + after = insn ? PREV_INSN (insn) : BB_END (bb);
> > > > > +
> > > > > + /* TLS_GD and TLS_LD_BASE instructions are normal functions which
> > > > > + clobber caller-saved registers. TLSDESC instructions are
> > > > > special
> > > > > + functions which only clobber RAX. If any registers clobbered by
> > > > > + the TLS instruction are live in this basic block, we must insert
> > > > > + the TLS instruction after all live registers clobbered by the
> > > > > TLS
> > > > > + instruction are dead. */
> > > > > +
> > > > > + auto_bitmap live_caller_saved_regs;
> > > > > + bitmap in = df_live ? DF_LIVE_IN (bb) : DF_LR_IN (bb);
> > > > > +
> > > > > + bool flags_live_p = bitmap_bit_p (in, FLAGS_REG);
> > > > > +
> > > > > + unsigned int i;
> > > > > +
> > > > > + /* Get all live caller-saved registers. */
> > > > > + if (kind == X86_CSE_TLSDESC)
> > > > > + {
> > > > > + if (bitmap_bit_p (in, AX_REG))
> > > > > + bitmap_set_bit (live_caller_saved_regs, AX_REG);
> > > >
> > > > And we don't need to check for those hard registers here and below?
> > >
> > > TLS_GD and TLS_LD_BASE instructions are normal functions which
> > > clobber caller-saved registers. TLSDESC instructions are special
> > > functions which only clobber RAX. live_caller_saved_regs captures
> > > live caller-saved registers for these TLS instructions.
>
> I notice those insns are CALL_INSN, and for ABI, rax/rdi/rsi is
> caller_saved registers, so even we explicitly use (clobber (reg: RAX))
Since a single TLS call will clobber caller-saved registers, it must
be placed where all caller-saved registers are dead. Otherwise, the
TLS call will clobber some live registers.
> RA will help save and restore the register?
This is unrelated to RA.
> > >
> > > rtx tls_symbol = XVECEXP (src, 0, 0);
> > > src = XVECEXP (src, 0, 1);
> > > ...
> > > rtx tls_set = PATTERN (set_insn);
> > > rtx tls_src = XVECEXP (SET_SRC (tls_set), 0, 0);
> > > if (!rtx_equal_p (tls_symbol, tls_src))
> > > {
> > > set_insn = nullptr;
> > > break;
> > > }
>
> According to @tls_dynamic_gnu2_64_<mode>, tls_src must be equal to
> tls_symbol, Do we really need to go through def-use chain to check
> that?
This verifies that checks the same pseudo register isn't assigned
to different tls_symbols.
> We may record the VAL as tls_symbol.
> > >
> > > >
> > > > > + {
> > > > > + if (DF_REF_IS_ARTIFICIAL (ref))
> > > > > + break;
> > > > > +
> > > > > + set_insn = DF_REF_INSN (ref);
> > > > > + tls64 = get_attr_tls64 (set_insn);
> > > > > + if (tls64 != TLS64_LEA)
> > > > > + {
> > > > > + set_insn = nullptr;
> > > > > + break;
> > > > > + }
> > > > > +
> > > > > + rtx tls_set = PATTERN (set_insn);
> > > > > + if (!tls_src)
> > > > > + tls_src = SET_SRC (tls_set);
> > > > > + else if (!rtx_equal_p (tls_src, SET_SRC (tls_set)))
> > > > > + {
> > > > > + set_insn = nullptr;
> > > > > + break;
> > > > > + }
> > > > > + }
> > > > > +
> > > > > + if (!set_insn)
> > > > > + return false;
> > > > > +
> > > > > + def_insn = set_insn;
> > > > > + }
> > > > > + else if (GET_CODE (src) == UNSPEC
> > > > > + && XINT (src, 1) == UNSPEC_TLSDESC
> > > > > + && SYMBOL_REF_P (XVECEXP (src, 0, 0)))
> > > > > + def_insn = nullptr;
> > > >
> > > > Similar for here, it's supposed to handle
> > > > "*tls_dynamic_gnu2_combine_64_<mode>", according to the splitter
> > > > pattern, the output value can also be CSEd with tls64_call when ever
> > > > symbol_ref in the second operand of PLUS is the same.
> > >
> > > v4 is changed to
> > >
> > > rtx tls_symbol = XVECEXP (src, 0, 0);
> > > src = XVECEXP (src, 0, 1);
> > > scalar_mode = mode = GET_MODE (src);
> > > gcc_assert (REG_P (src));
> >
> > Since this triggered the assert on
> >
> > (set (reg/f:DI 103)
> > (plus:DI (unspec:DI [
> > (symbol_ref:DI ("_TLS_MODULE_BASE_") [flags 0x10])
> > (unspec:DI [
> > (symbol_ref:DI ("_TLS_MODULE_BASE_") [flags 0x10])
> > ] UNSPEC_TLSDESC)
> > (reg/f:DI 7 sp)
> > ] UNSPEC_TLSDESC)
> > (const:DI (unspec:DI [
> > (symbol_ref:DI ("foo") [flags 0x1a] <var_decl
> > 0x7fffe99dbe40 foo>)
> > ] UNSPEC_DTPOFF))))
> >
> > I added a testcase and kept the v3 code.
>
> For tls64 combine, tls_symbol should be second operand of the original src,
> .i.e
> (const:DI (unspec:DI [
> (symbol_ref:DI ("foo") [flags 0x1a] <var_decl
> 0x7fffe99dbe40 foo>) <--- this
> ] UNSPEC_DTPOFF))))
>
> Not this (symbol_ref:DI ("_TLS_MODULE_BASE_"), and no need for
> gcc_assert (REG_P (src)).
This has been changed to
if (REG_P (src))
{
....
}
else if (GET_CODE (src) == UNSPEC
&& XINT (src, 1) == UNSPEC_TLSDESC
&& SYMBOL_REF_P (XVECEXP (src, 0, 0)))
def_insn = nullptr;
else
gcc_unreachable ();
in v5:
https://patchwork.sourceware.org/project/gcc/list/?series=50446
H.J.
