RISC-V: Implement TLS Descriptors.

This implements TLS Descriptors (TLSDESC) as specified in [1].

The 4-instruction sequence is implemented as a single RTX insn for
simplicity, but this can be revisited later if instruction scheduling or
more flexible RA is desired.

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.
	* doc/install.texi: Document --with-tls for RISC-V.
	* doc/invoke.texi: Document -mtls-dialect for RISC-V.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/tls_1.x: Add TLSDESC GD test case.
	* gcc.target/riscv/tlsdesc.c: Same as above.

diff --git a/gcc/config.gcc b/gcc/config.gcc
index e62f98e93f47ffaf197fa5eeab2c485b57c37c40..2e320dd26c5e83afa3382ce2278c4054c53c81cd 100644 (file)
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -2492,6 +2492,7 @@ riscv*-*-linux*)
        # Force .init_array support.  The configure script cannot always
        # automatically detect that GAS supports it, yet we require it.
        gcc_cv_initfini_array=yes
+       with_tls=${with_tls:-trad}
        ;;
 riscv*-*-elf* | riscv*-*-rtems*)
        tm_file="elfos.h newlib-stdint.h ${tm_file} riscv/elf.h"
@@ -2534,6 +2535,7 @@ riscv*-*-freebsd*)
        # Force .init_array support.  The configure script cannot always
        # automatically detect that GAS supports it, yet we require it.
        gcc_cv_initfini_array=yes
+       with_tls=${with_tls:-trad}
        ;;
 
 loongarch*-*-linux*)
@@ -4671,7 +4673,7 @@ case "${target}" in
                ;;
 
        riscv*-*-*)
-               supported_defaults="abi arch tune riscv_attribute isa_spec"
+               supported_defaults="abi arch tune riscv_attribute isa_spec tls"
 
                case "${target}" in
                riscv-* | riscv32*) xlen=32 ;;
@@ -4801,6 +4803,17 @@ case "${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
 
                # Handle --with-multilib-list.
                if test "x${with_multilib_list}" != xdefault; then

diff --git a/gcc/config/riscv/riscv-opts.h b/gcc/config/riscv/riscv-opts.h
index 392b9169240df66127efd1a94caacaae7e8829f8..1b2dd5757a8e1508fbc5fb11c8c0fde497e73bad 100644 (file)
--- a/gcc/config/riscv/riscv-opts.h
+++ b/gcc/config/riscv/riscv-opts.h
@@ -154,4 +154,10 @@ enum rvv_vector_bits_enum {
 #define TARGET_MAX_LMUL                                                        \
   (int) (rvv_max_lmul == RVV_DYNAMIC ? RVV_M8 : rvv_max_lmul)
 
+/* TLS types.  */
+enum riscv_tls_type {
+  TLS_TRADITIONAL,
+  TLS_DESCRIPTORS
+};
+
 #endif /* ! GCC_RISCV_OPTS_H */

diff --git a/gcc/config/riscv/riscv-protos.h b/gcc/config/riscv/riscv-protos.h
index 4677d9c46cd2217911a9cddaea221efaf571fd1f..5d46a29d8b70030edb0e72f3c9f609af02e982c7 100644 (file)
--- a/gcc/config/riscv/riscv-protos.h
+++ b/gcc/config/riscv/riscv-protos.h
@@ -34,9 +34,10 @@ enum riscv_symbol_type {
   SYMBOL_TLS,
   SYMBOL_TLS_LE,
   SYMBOL_TLS_IE,
-  SYMBOL_TLS_GD
+  SYMBOL_TLS_GD,
+  SYMBOL_TLSDESC,
 };
-#define NUM_SYMBOL_TYPES (SYMBOL_TLS_GD + 1)
+#define NUM_SYMBOL_TYPES (SYMBOL_TLSDESC + 1)
 
 /* Classifies an address.
 

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 2a71badfdc9fae5800cfab02711a8c4a831fdd72..00defa69fd8e83fbc45858f94b29d11c04f0f169 100644 (file)
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -1072,6 +1072,7 @@ static int riscv_symbol_insns (enum riscv_symbol_type type)
     case SYMBOL_ABSOLUTE: return 2; /* LUI + the reference.  */
     case SYMBOL_PCREL: return 2; /* AUIPC + the reference.  */
     case SYMBOL_TLS_LE: return 3; /* LUI + ADD TP + the reference.  */
+    case SYMBOL_TLSDESC: return 6; /* 4-instruction call + ADD TP + the reference.  */
     case SYMBOL_GOT_DISP: return 3; /* AUIPC + LD GOT + the reference.  */
     case SYMBOL_FORCE_TO_MEM: return 3; /* AUIPC + LD + the reference.  */
     default: gcc_unreachable ();
@@ -2220,7 +2221,7 @@ riscv_call_tls_get_addr (rtx sym, rtx result)
 static rtx
 riscv_legitimize_tls_address (rtx loc)
 {
-  rtx dest, tp, tmp;
+  rtx dest, tp, tmp, a0;
   enum tls_model model = SYMBOL_REF_TLS_MODEL (loc);
 
 #if 0
@@ -2236,9 +2237,24 @@ riscv_legitimize_tls_address (rtx loc)
       /* Rely on section anchors for the optimization that LDM TLS
         provides.  The anchor's address is loaded with GD TLS. */
     case TLS_MODEL_GLOBAL_DYNAMIC:
-      tmp = gen_rtx_REG (Pmode, GP_RETURN);
-      dest = gen_reg_rtx (Pmode);
-      emit_libcall_block (riscv_call_tls_get_addr (loc, tmp), dest, tmp, loc);
+      if (TARGET_TLSDESC)
+       {
+         static unsigned seqno;
+         tp = gen_rtx_REG (Pmode, THREAD_POINTER_REGNUM);
+         a0 = gen_rtx_REG (Pmode, GP_ARG_FIRST);
+         dest = gen_reg_rtx (Pmode);
+
+         emit_insn (gen_tlsdesc (Pmode, loc, GEN_INT (seqno)));
+         emit_insn (gen_add3_insn (dest, a0, tp));
+         seqno++;
+       }
+      else
+       {
+         tmp = gen_rtx_REG (Pmode, GP_RETURN);
+         dest = gen_reg_rtx (Pmode);
+         emit_libcall_block (riscv_call_tls_get_addr (loc, tmp), dest, tmp,
+                             loc);
+       }
       break;
 
     case TLS_MODEL_INITIAL_EXEC:

diff --git a/gcc/config/riscv/riscv.h b/gcc/config/riscv/riscv.h
index d5779512994df3e435869732e88ee12a3cd5ae63..269b8c1f076379c7ced8afe2bc2493747ef636c6 100644 (file)
--- a/gcc/config/riscv/riscv.h
+++ b/gcc/config/riscv/riscv.h
@@ -64,6 +64,7 @@ extern const char *riscv_arch_help (int argc, const char **argv);
    --with-abi is ignored if -mabi is specified.
    --with-tune is ignored if -mtune or -mcpu is specified.
    --with-isa-spec is ignored if -misa-spec is specified.
+   --with-tls is ignored if -mtls-dialect is specified.
 
    But using default -march/-mtune value if -mcpu don't have valid option.  */
 #define OPTION_DEFAULT_SPECS \
@@ -73,8 +74,9 @@ extern const char *riscv_arch_help (int argc, const char **argv);
   {"arch", "%{!march=*:"                                               \
           "  %{!mcpu=*:-march=%(VALUE)}"                               \
           "  %{mcpu=*:%:riscv_expand_arch_from_cpu(%* %(VALUE))}}" },  \
-  {"abi", "%{!mabi=*:-mabi=%(VALUE)}" }, \
-  {"isa_spec", "%{!misa-spec=*:-misa-spec=%(VALUE)}" }, \
+  {"abi", "%{!mabi=*:-mabi=%(VALUE)}" },                               \
+  {"isa_spec", "%{!misa-spec=*:-misa-spec=%(VALUE)}" },                        \
+  {"tls", "%{!mtls-dialect=*:-mtls-dialect=%(VALUE)}"},                \
 
 #ifdef IN_LIBGCC2
 #undef TARGET_64BIT
@@ -1228,4 +1230,7 @@ extern void riscv_remove_unneeded_save_restore_calls (void);
 #define HAVE_POST_MODIFY_DISP TARGET_XTHEADMEMIDX
 #define HAVE_PRE_MODIFY_DISP  TARGET_XTHEADMEMIDX
 
+/* Check TLS Descriptors mechanism is selected.  */
+#define TARGET_TLSDESC (riscv_tls_dialect == TLS_DESCRIPTORS)
+
 #endif /* ! GCC_RISCV_H */

diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index 0346cc3859d8e865cb550fd45c4f06cd449ad6d9..c2b4323c53a789c9e6212660af86cc60e89067e9 100644 (file)
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -48,7 +48,7 @@
   UNSPEC_TLS_LE
   UNSPEC_TLS_IE
   UNSPEC_TLS_GD
-
+  UNSPEC_TLSDESC
   ;; High part of PC-relative address.
   UNSPEC_AUIPC
 
@@ -2089,6 +2089,24 @@
    (set_attr "type" "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:P 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>")])
+
 (define_insn "auipc<mode>"
   [(set (match_operand:P           0 "register_operand" "=r")
        (unspec:P

diff --git a/gcc/config/riscv/riscv.opt b/gcc/config/riscv/riscv.opt
index 7d625af02d52f86f03a4b30c627c9216451aac34..8da0764eb4becb5cff38e7ef14a1d781922d667f 100644 (file)
--- a/gcc/config/riscv/riscv.opt
+++ b/gcc/config/riscv/riscv.opt
@@ -606,3 +606,17 @@ Enum(rvv_vector_bits) String(zvl) Value(RVV_VECTOR_BITS_ZVL)
 mrvv-vector-bits=
 Target RejectNegative Joined Enum(rvv_vector_bits) Var(rvv_vector_bits) Init(RVV_VECTOR_BITS_SCALABLE)
 -mrvv-vector-bits=<string>     Set the kind of bits for an RVV vector register.
+
+Enum
+Name(tls_type) Type(enum riscv_tls_type)
+The possible TLS dialects:
+
+EnumValue
+Enum(tls_type) String(trad) Value(TLS_TRADITIONAL)
+
+EnumValue
+Enum(tls_type) String(desc) Value(TLS_DESCRIPTORS)
+
+mtls-dialect=
+Target RejectNegative Joined Enum(tls_type) Var(riscv_tls_dialect) Init(TLS_TRADITIONAL) Save
+Specify TLS dialect.

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 970b1a67e7429e00a6843f295c86dde31573b677..1c58dc334ab2bdb6253b61ca441828ab7619ce6c 100644 (file)
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1187,6 +1187,9 @@ Specify the default TLS dialect, for systems were there is a choice.
 For ARM targets, possible values for @var{dialect} are @code{gnu} or
 @code{gnu2}, which select between the original GNU dialect and the GNU TLS
 descriptor-based dialect.
+For RISC-V targets, possible values for @var{dialect} are @code{trad} or
+@code{desc}, which select between the traditional GNU dialect and the GNU TLS
+descriptor-based dialect.
 
 @item --enable-multiarch
 Specify whether to enable or disable multiarch support.  The default is

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 1006510fc6aaf0d50d1a045fcd63f99d06b2e8d9..f5f5d83f8179b40203d49be9169af0bf2bfeec18 100644 (file)
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1265,7 +1265,8 @@ See RS/6000 and PowerPC Options.
 -minline-atomics  -mno-inline-atomics
 -minline-strlen  -mno-inline-strlen
 -minline-strcmp  -mno-inline-strcmp
--minline-strncmp  -mno-inline-strncmp}
+-minline-strncmp  -mno-inline-strncmp
+-mtls-dialect=desc  -mtls-dialect=trad}
 
 @emph{RL78 Options}
 @gccoptlist{-msim  -mmul=none  -mmul=g13  -mmul=g14  -mallregs
@@ -31063,6 +31064,16 @@ which register to use as base register for reading the canary,
 and from what offset from that base register. There is no default
 register or offset as this is entirely for use within the Linux
 kernel.
+
+@opindex mtls-dialect=desc
+@item -mtls-dialect=desc
+Use TLS descriptors as the thread-local storage mechanism for dynamic accesses
+of TLS variables.
+
+@opindex mtls-dialect=trad
+@item -mtls-dialect=trad
+Use traditional TLS as the thread-local storage mechanism for dynamic accesses
+of TLS variables.  This is the default.
 @end table
 
 @node RL78 Options

diff --git a/gcc/testsuite/gcc.target/riscv/tls_1.x b/gcc/testsuite/gcc.target/riscv/tls_1.x
new file mode 100644 (file)
index 0000000..cf334ef
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/tls_1.x
@@ -0,0 +1,5 @@
+extern __thread unsigned gd;
+
+unsigned get() {
+       return gd;
+}

diff --git a/gcc/testsuite/gcc.target/riscv/tlsdesc.c b/gcc/testsuite/gcc.target/riscv/tlsdesc.c
new file mode 100644 (file)
index 0000000..f9ac9fe
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/tlsdesc.c
@@ -0,0 +1,12 @@
+/* { dg-require-effective-target tls_native } */
+/* { dg-options "-O2 -fpic -mtls-dialect=desc --save-temps" } */
+/* { dg-require-effective-target fpic } */
+
+#include "tls_1.x"
+
+/* { dg-final { scan-assembler-times "auipc\t\[a-x0-9\]+,%tlsdesc_hi" 1 } } */
+/* { dg-final { scan-assembler-times "lw\t\[a-x0-9\]+,%tlsdesc_load_lo" 1 { target { rv32 } } } } */
+/* { dg-final { scan-assembler-times "ld\t\[a-x0-9\]+,%tlsdesc_load_lo" 1 { target { rv64 } } } }*/
+/* { dg-final { scan-assembler-times "addi\ta0,\[a-x0-9\]+,%tlsdesc_add_lo" 1 } } */
+/* { dg-final { scan-assembler-times "jalr\tt0,\[a-x0-9\]+,%tlsdesc_call" 1 } } */
+/* { dg-final { cleanup-saved-temps } } */