On 9/8/23 04:49, Tatsuyuki Ishi via Gcc-patches wrote:
This implements TLS Descriptors (TLSDESC) as specified in [1].
In TLSDESC instruction sequence, the first instruction relocates against
the target TLS variable, while subsequent instructions relocates against
the address of the first. Such usage of labels are not well-supported
within GCC. Due to this, the 4-instruction sequence is implemented as a
single RTX insn.
The default remains to be the traditional TLS model, but can be configured
with --with_tls={trad,desc}. The choice can be revisited once toolchain
and libc support ships.
[1]: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/373.
gcc/Changelog:
* config/riscv/riscv.opt: Add -mtls-dialect to configure TLS flavor.
* config.gcc: Add --with_tls configuration option to change the default
TLS flavor.
* config/riscv/riscv.h: Add TARGET_TLSDESC determined from
-mtls-dialect and with_tls defaults.
* config/riscv/riscv-opts.h: Define enum riscv_tls_type for the two TLS
flavors.
* config/riscv/riscv-protos.h: Define SYMBOL_TLSDESC symbol type.
* config/riscv/riscv.md: Add instruction sequence for TLSDESC.
* config/riscv/riscv.cc (riscv_symbol_insns): Add instruction sequence
length data for TLSDESC.
(riscv_legitimize_tls_address): Add lowering of TLSDESC.
---
@@ -4694,6 +4696,17 @@ case "${target}" in
;;
esac
fi
+ # Handle --with-tls.
+ case "$with_tls" in
+ "" \
+ | trad | desc)
+ # OK
+ ;;
+ *)
+ echo "Unknown TLS method used in --with-tls=$with_tls" 1>&2
+ exit 1
+ ;;
+ esac
Is there a reason why this isn't formatted like the other cases?
@@ -1869,6 +1870,24 @@
[(set_attr "got" "load")
(set_attr "mode" "<MODE>")])
+(define_insn "@tlsdesc<mode>"
+ [(set (reg:P A0_REGNUM)
+ (unspec:P
+ [(match_operand:P 0 "symbolic_operand" "")
+ (match_operand:P 1 "const_int_operand")]
+ UNSPEC_TLSDESC))
+ (clobber (reg:SI T0_REGNUM))]
+ "TARGET_TLSDESC"
+ {
+ return ".LT%1: auipc\ta0, %%tlsdesc_hi(%0)\;"
+ "<load>\tt0,%%tlsdesc_load_lo(.LT%1)(a0)\;"
+ "addi\ta0,a0,%%tlsdesc_add_lo(.LT%1)\;"
+ "jalr\tt0,t0,%%tlsdesc_call(.LT%1)";
+ }
+ [(set_attr "type" "multi")
+ (set_attr "length" "16")
+ (set_attr "mode" "<MODE>")])
Hmm, I would be a bit worried about explicitly using $a0 here. That's
generally frowned upon, but probably unavoidable in this case since this
is a call under the hood.
This needs changes to invoke.texi since it introduces new options. I
don't think it has to be anything terribly verbose. A one liner is
probably sufficient and I wouldn't be surprised if other ports have
suitable text we could copy.
So overall if Kito's OK, then I am with the trivial doc change and
perhaps the formatting fix in config.guess.
jeff
