aarch64: Add march flags for +the and +d128 arch extensions

Given the introduction of optional 128-bit page table descriptor and
translation hardening extension support with the Arm9.4-a
architecture, this introduces the relevant flags to enable the reading
and writing of 128-bit system registers.

The `+d128' -march modifier enables the use of the following ACLE
builtin functions:

  * __uint128_t __arm_rsr128(const char *special_register);
  * void __arm_wsr128(const char *special_register, __uint128_t value);

and defines the __ARM_FEATURE_SYSREG128 macro to 1.

Finally, the `rcwmask_el1' and `rcwsmask_el1' 128-bit system register
implementations are also reliant on the enablement of the `+the' flag,
which is thus also implemented in this patch.

gcc/ChangeLog:

	* config/aarch64/aarch64-c.cc (__ARM_FEATURE_SYSREG128): New.
	* config/aarch64/aarch64-arches.def (armv8.9-a): New.
	(armv9.4-a): Likewise.
	* config/aarch64/aarch64-option-extensions.def (d128): Likewise.
	(the): Likewise.
	* config/aarch64/aarch64.h (AARCH64_ISA_V9_4A): Likewise.
	(AARCH64_ISA_V8_9A): Likewise.
	(TARGET_ARMV9_4): Likewise.
	(AARCH64_ISA_D128): Likewise.
	(AARCH64_ISA_THE): Likewise.
	(TARGET_D128): Likewise.
	* doc/invoke.texi (AArch64 Options): Document new -march flags
	and extensions.

Author: Victor Do Nascimento

gcc/config/aarch64/aarch64-arches.def

@@ -39,10 +39,12 @@ AARCH64_ARCH("armv8.5-a",     generic_armv8_a,   V8_5A,     8,  (V8_4A, SB, SSBS
 AARCH64_ARCH("armv8.6-a",     generic_armv8_a,   V8_6A,     8,  (V8_5A, I8MM, BF16))
 AARCH64_ARCH("armv8.7-a",     generic_armv8_a,   V8_7A,     8,  (V8_6A, LS64))
 AARCH64_ARCH("armv8.8-a",     generic_armv8_a,   V8_8A,     8,  (V8_7A, MOPS))
+AARCH64_ARCH("armv8.9-a",     generic_armv8_a,   V8_9A,     8,  (V8_8A))
 AARCH64_ARCH("armv8-r",       generic_armv8_a,   V8R  ,     8,  (V8_4A))
 AARCH64_ARCH("armv9-a",       generic_armv9_a,   V9A  ,     9,  (V8_5A, SVE2))
 AARCH64_ARCH("armv9.1-a",     generic_armv9_a,   V9_1A,     9,  (V8_6A, V9A))
 AARCH64_ARCH("armv9.2-a",     generic_armv9_a,   V9_2A,     9,  (V8_7A, V9_1A))
 AARCH64_ARCH("armv9.3-a",     generic_armv9_a,   V9_3A,     9,  (V8_8A, V9_2A))
+AARCH64_ARCH("armv9.4-a",     generic_armv9_a,   V9_4A,     9,  (V8_9A, V9_3A))
 
 #undef AARCH64_ARCH

gcc/config/aarch64/aarch64-c.cc

@@ -254,6 +254,7 @@ aarch64_update_cpp_builtins (cpp_reader *pfile)
   aarch64_def_or_undef (TARGET_LS64,
 			"__ARM_FEATURE_LS64", pfile);
   aarch64_def_or_undef (AARCH64_ISA_RCPC, "__ARM_FEATURE_RCPC", pfile);
+  aarch64_def_or_undef (TARGET_D128, "__ARM_FEATURE_SYSREG128", pfile);
 
   aarch64_def_or_undef (TARGET_SME, "__ARM_FEATURE_SME", pfile);
   aarch64_def_or_undef (TARGET_SME_I16I64, "__ARM_FEATURE_SME_I16I64", pfile);

gcc/config/aarch64/aarch64-option-extensions.def

@@ -159,4 +159,8 @@ AARCH64_OPT_EXTENSION("sme-f64f64", SME_F64F64, (SME), (), (), "")
 
 AARCH64_OPT_EXTENSION("sme2", SME2, (SME), (), (), "sme2")
 
+AARCH64_OPT_EXTENSION("d128", D128, (), (), (), "d128")
+
+AARCH64_OPT_EXTENSION("the", THE, (), (), (), "the")
+
 #undef AARCH64_OPT_EXTENSION

gcc/config/aarch64/aarch64.h

@@ -254,13 +254,17 @@ constexpr auto AARCH64_FL_DEFAULT_ISA_MODE = AARCH64_FL_SM_OFF;
 #define AARCH64_ISA_PAUTH	   (aarch64_isa_flags & AARCH64_FL_PAUTH)
 #define AARCH64_ISA_V8_7A	   (aarch64_isa_flags & AARCH64_FL_V8_7A)
 #define AARCH64_ISA_V8_8A	   (aarch64_isa_flags & AARCH64_FL_V8_8A)
+#define AARCH64_ISA_V8_9A	   (aarch64_isa_flags & AARCH64_FL_V8_9A)
 #define AARCH64_ISA_V9A		   (aarch64_isa_flags & AARCH64_FL_V9A)
 #define AARCH64_ISA_V9_1A          (aarch64_isa_flags & AARCH64_FL_V9_1A)
 #define AARCH64_ISA_V9_2A          (aarch64_isa_flags & AARCH64_FL_V9_2A)
 #define AARCH64_ISA_V9_3A          (aarch64_isa_flags & AARCH64_FL_V9_3A)
+#define AARCH64_ISA_V9_4A	   (aarch64_isa_flags & AARCH64_FL_V9_4A)
 #define AARCH64_ISA_MOPS	   (aarch64_isa_flags & AARCH64_FL_MOPS)
 #define AARCH64_ISA_LS64	   (aarch64_isa_flags & AARCH64_FL_LS64)
 #define AARCH64_ISA_CSSC	   (aarch64_isa_flags & AARCH64_FL_CSSC)
+#define AARCH64_ISA_D128	   (aarch64_isa_flags & AARCH64_FL_D128)
+#define AARCH64_ISA_THE		   (aarch64_isa_flags & AARCH64_FL_THE)
 
 /* The current function is a normal non-streaming function.  */
 #define TARGET_NON_STREAMING (AARCH64_ISA_SM_OFF)
@@ -450,6 +454,17 @@ constexpr auto AARCH64_FL_DEFAULT_ISA_MODE = AARCH64_FL_SM_OFF;
 /* ARMv8.1-A Adv.SIMD support.  */
 #define TARGET_SIMD_RDMA (TARGET_SIMD && AARCH64_ISA_RDMA)
 
+/* Armv9.4-A features.  */
+#define TARGET_ARMV9_4 (AARCH64_ISA_V9_4A)
+
+/*  128-bit System Registers and Instructions from Armv9.4-a are enabled
+    through +d128.  */
+#define TARGET_D128 (AARCH64_ISA_D128)
+
+/*  Armv8.9-A/9.4-A Translation Hardening Extension system registers are
+    enabled through +the.  */
+#define TARGET_THE (AARCH64_ISA_THE)
+
 /* Standard register usage.  */
 
 /* 31 64-bit general purpose registers R0-R30:

gcc/doc/invoke.texi

@@ -21045,10 +21045,12 @@ and the features that they enable by default:
 @item @samp{armv8.6-a} @tab Armv8.6-A @tab @samp{armv8.5-a}, @samp{+bf16}, @samp{+i8mm}
 @item @samp{armv8.7-a} @tab Armv8.7-A @tab @samp{armv8.6-a}, @samp{+ls64}
 @item @samp{armv8.8-a} @tab Armv8.8-a @tab @samp{armv8.7-a}, @samp{+mops}
+@item @samp{armv8.9-a} @tab Armv8.9-a @tab @samp{armv8.8-a}
 @item @samp{armv9-a} @tab Armv9-A @tab @samp{armv8.5-a}, @samp{+sve}, @samp{+sve2}
 @item @samp{armv9.1-a} @tab Armv9.1-A @tab @samp{armv9-a}, @samp{+bf16}, @samp{+i8mm}
 @item @samp{armv9.2-a} @tab Armv9.2-A @tab @samp{armv9.1-a}, @samp{+ls64}
 @item @samp{armv9.3-a} @tab Armv9.3-A @tab @samp{armv9.2-a}, @samp{+mops}
+@item @samp{armv9.4-a} @tab Armv9.4-A @tab @samp{armv9.3-a}
 @item @samp{armv8-r} @tab Armv8-R @tab @samp{armv8-r}
 @end multitable
 
@@ -21359,6 +21361,11 @@ Enable the FEAT_SME_I16I64 extension to SME.
 Enable the FEAT_SME_F64F64 extension to SME.
 +@item sme2
 Enable the Scalable Matrix Extension 2.  This also enables SME instructions.
+@item d128
+Enable support for 128-bit system register read/write instructions.
+@item the
+Enable support for Armv8.9-a/9.4-a translation hardening extension.
+
 @end table
 
 Feature @option{crypto} implies @option{aes}, @option{sha2}, and @option{simd},