Re: [AArch64][TLSGD][2/2] Implement TLS GD traditional for tiny code model

[Jiong Wang <jiong.wang@foss.arm.com>]

On 05/11/15 14:57, Jiong Wang wrote:
> Marcus Shawcroft writes:
>
>> +#ifdef HAVE_AS_TINY_TLSGD_RELOCS
>> +  return SYMBOL_TINY_TLSGD;
>> +#else
>> +  return SYMBOL_SMALL_TLSGD;
>> +#endif
>>
>> Rather than introduce blocks of conditional compilation it is better
>> to gate different behaviours with a test on a constant expression. In
>> this case add something like this:
>>
>> #if define(HAVE_AS_TINY_TLSGD_RELOCS)
>> #define USE_TINY_TLSGD 1
>> #else
>> #define USE_TINY_TLSGD 0
>> #endif
>>
>> up near the definition of TARGET_HAVE_TLS then write the above
>> fragment without using the preprocessor:
>>
>> return USE_TINY_TLSGD ? SYMBOL_TINY_TLSGD : SYMBOL_SMALL_TLSGD;
>
> Done.
>
>> - aarch64_emit_call_insn (gen_tlsgd_small (result, imm, resolver));
>> + if (type == SYMBOL_SMALL_TLSGD)
>> +  aarch64_emit_call_insn (gen_tlsgd_small (result, imm, resolver));
>> + else
>> +  aarch64_emit_call_insn (gen_tlsgd_tiny (result, imm, resolver));
>>   insns = get_insns ();
>>   end_sequence ();
>>
>> Add a separate case statment for SYMBOL_TINY_TLSGD rather than reusing
>> the case statement for SYMBOL_SMALL_TLSGD and then needing to add
>> another test against symbol type within the body of the case
>> statement.
>
> Done.
>
>>
>> +(define_insn "tlsgd_tiny"
>> +  [(set (match_operand 0 "register_operand" "")
>> + (call (mem:DI (match_operand:DI 2 "" "")) (const_int 1)))
>> +   (unspec:DI [(match_operand:DI 1 "aarch64_valid_symref" "S")]
>> UNSPEC_GOTTINYTLS)
>> +   (clobber (reg:DI LR_REGNUM))
>> +  ]
>> +  ""
>> +  "adr\tx0, %A1;bl\t%2;nop";
>> +  [(set_attr "type" "multiple")
>> +   (set_attr "length" "12")])
>>
>> I don't think the explicit clobber LR_REGNUM is required since your
>> change last September:
>> https://gcc.gnu.org/ml/gcc-patches/2014-09/msg02654.html
>
> We don't need this explict clobber LR_REGNUM only if operand 0 happen
> be allocated to LR_REGNUM as after my above patch LR_REGNUM is allocable.
>
> However we still need the explict clobber here.  Because for all other
> cases LR_REGNUM not allocated, gcc data flow analysis can't deduct 
> LR_REGNUM
> will still be clobbered implicitly by the call instruction.
>
> Without this "clobber" tag, a direct impact is df_regs_ever_live is 
> calculated
> incorrectly for x30, then for the following simple testcase:
>
> __thread int t0 = 0x10;
> __thread int t1 = 0x10;
>
> int
> main (int argc, char **argv)
> {
>   if (t0 != t1)
>     return 1;
>   return  0;
> }
>
>
> if you compile with
>
>  "-O2 -ftls-model=global-dynamic -fpic -mtls-dialect=trad t.c 
> -mcmodel=tiny -fomit-frame-pointer",
> wrong code will be generated:
>
>  main:
>         str     x19, [sp, -16]!  <--- x30 is not saved.
>         adr     x0, :tlsgd:t0
>         bl __tls_get_addr
>         nop
>
> Patch updated. tls regression OK
>
> OK for trunk?
>
> 2015-11-05  Jiong Wang  <jiong.wang@arm.com>
>
> gcc/
>   * configure.ac: Add check for binutils global dynamic tiny code model
>   relocation support.
>   * configure: Regenerate.
>   * config.in: Regenerate.
>   * config/aarch64/aarch64.md (tlsgd_tiny): New define_insn.
>   * config/aarch64/aarch64-protos.h (aarch64_symbol_type): New
>   enumeration SYMBOL_TINY_TLSGD.
>   (aarch64_symbol_context): New comment on SYMBOL_TINY_TLSGD.
>   * config/aarch64/aarch64.c (aarch64_classify_tls_symbol): Support
>   SYMBOL_TINY_TLSGD.
>   (aarch64_print_operand): Likewise.
>   (aarch64_expand_mov_immediate): Likewise.
>   (aarch64_load_symref_appropriately): Likewise.
>
> gcc/testsuite/
>   * lib/target-supports.exp (check_effective_target_aarch64_tlsgdtiny):
>   New effective check.
>   * gcc.target/aarch64/tlsgd_small_1.c: New testcase.
>   * gcc.target/aarch64/tlsgd_small_ilp32_1.c: Likewise.
>   * gcc.target/aarch64/tlsgd_tiny_1.c: Likewise.
>   * gcc.target/aarch64/tlsgd_tiny_ilp32_1.c: Likewise.
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