[PATCH V3 2/6] aarch64: Add support for aarch64-sys-regs.def

[Victor Do Nascimento <victor.donascimento@arm.com>]

This patch defines the structure of a new .def file used for
representing the aarch64 system registers, what information it should
hold and the basic framework in GCC to process this file.

Entries in the aarch64-system-regs.def file should be as follows:

  SYSREG (NAME, CPENC (sn,op1,cn,cm,op2), FLAG1 | ... | FLAGn, ARCH)

Where the arguments to SYSREG correspond to:
  - NAME:  The system register name, as used in the assembly language.
  - CPENC: The system register encoding, mapping to:

    	       s<sn>_<op1>_c<cn>_c<cm>_<op2>

  - FLAG: The entries in the FLAGS field are bitwise-OR'd together to
    	  encode extra information required to ensure proper use of
	  the system register.  For example, a read-only system
	  register will have the flag F_REG_READ, while write-only
	  registers will be labeled F_REG_WRITE.  Such flags are
	  tested against at compile-time.
  - ARCH: The architectural features the system register is associated
    	  with.  This is encoded via one of three possible macros:
	  1. When a system register is universally implemented, we say
	  it has no feature requirements, so we tag it with the
	  AARCH64_NO_FEATURES macro.
	  2. When a register is only implemented for a single
	  architectural extension EXT, the AARCH64_FEATURE (EXT), is
	  used.
	  3. When a given system register is made available by any of N
	  possible architectural extensions, the AARCH64_FEATURES(N, ...)
	  macro is used to combine them accordingly.

In order to enable proper interpretation of the SYSREG entries by the
compiler, flags defining system register behavior such as `F_REG_READ'
and `F_REG_WRITE' are also defined here, so they can later be used for
the validation of system register properties.

Finally, any architectural feature flags from Binutils missing from GCC
have appropriate aliases defined here so as to ensure
cross-compatibility of SYSREG entries across the toolchain.

gcc/ChangeLog:

	* config/aarch64/aarch64.cc (sysreg_t): New.
	(sysreg_structs): Likewise.
	(nsysreg): Likewise.
	(AARCH64_FEATURE): Likewise.
	(AARCH64_FEATURES): Likewise.
	(AARCH64_NO_FEATURES): Likewise.
	* config/aarch64/aarch64.h (AARCH64_ISA_V8A): Add missing
	ISA flag.
	(AARCH64_ISA_V8_1A): Likewise.
	(AARCH64_ISA_V8_7A): Likewise.
	(AARCH64_ISA_V8_8A): Likewise.
	(AARCH64_NO_FEATURES): Likewise.
	(AARCH64_FL_RAS): New ISA flag alias.
	(AARCH64_FL_LOR): Likewise.
	(AARCH64_FL_PAN): Likewise.
	(AARCH64_FL_AMU): Likewise.
	(AARCH64_FL_SCXTNUM): Likewise.
	(AARCH64_FL_ID_PFR2): Likewise.
	(F_DEPRECATED): New.
	(F_REG_READ): Likewise.
	(F_REG_WRITE): Likewise.
	(F_ARCHEXT): Likewise.
	(F_REG_ALIAS): Likewise.
---
 gcc/config/aarch64/aarch64.cc | 53 +++++++++++++++++++++++++++++++++++
 gcc/config/aarch64/aarch64.h  | 22 +++++++++++++++
 2 files changed, 75 insertions(+)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 5fd7063663c..a4a9e2e51ea 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -2806,6 +2806,59 @@ static const struct processor all_cores[] =
    feature_deps::V8A ().enable, &generic_tunings},
   {NULL, aarch64_none, aarch64_none, aarch64_no_arch, 0, NULL}
 };
+/* Internal representation of system registers.  */
+typedef struct {
+  const char *name;
+  /* Stringified sysreg encoding values, represented as
+     s<sn>_<op1>_c<cn>_c<cm>_<op2>.  */
+  const char *encoding;
+  /* Flags affecting sysreg usage, such as read/write-only.  */
+  unsigned properties;
+  /* Architectural features implied by sysreg.  */
+  aarch64_feature_flags arch_reqs;
+} sysreg_t;
+
+/* An aarch64_feature_set initializer for a single feature,
+   AARCH64_FEATURE_<FEAT>.  */
+#define AARCH64_FEATURE(FEAT) AARCH64_FL_##FEAT
+
+/* Used by AARCH64_FEATURES.  */
+#define AARCH64_OR_FEATURES_1(X, F1) \
+  AARCH64_FEATURE (F1)
+#define AARCH64_OR_FEATURES_2(X, F1, F2) \
+  (AARCH64_FEATURE (F1) | AARCH64_OR_FEATURES_1 (X, F2))
+#define AARCH64_OR_FEATURES_3(X, F1, ...) \
+  (AARCH64_FEATURE (F1) | AARCH64_OR_FEATURES_2 (X, __VA_ARGS__))
+
+/* An aarch64_feature_set initializer for the N features listed in "...".  */
+#define AARCH64_FEATURES(N, ...) \
+  AARCH64_OR_FEATURES_##N (0, __VA_ARGS__)
+
+#define AARCH64_NO_FEATURES	   0
+
+/* Flags associated with the properties of system registers.  It mainly serves
+   to mark particular registers as read or write only.  */
+#define F_DEPRECATED		   (1 << 1)
+#define F_REG_READ		   (1 << 2)
+#define F_REG_WRITE		   (1 << 3)
+#define F_ARCHEXT		   (1 << 4)
+/* Flag indicating register name is alias for another system register.  */
+#define F_REG_ALIAS		   (1 << 5)
+
+/* Database of system registers, their encodings and architectural
+   requirements.  */
+const sysreg_t sysreg_structs[] =
+{
+#define CPENC(SN, OP1, CN, CM, OP2) "s"#SN"_"#OP1"_c"#CN"_c"#CM"_"#OP2
+#define SYSREG(NAME, ENC, FLAGS, ARCH) \
+  { NAME, ENC, FLAGS, ARCH },
+#include "aarch64-sys-regs.def"
+#undef CPENC
+};
+
+#undef AARCH64_NO_FEATURES
+
+const unsigned nsysreg = ARRAY_SIZE (sysreg_structs);
 
 /* The current tuning set.  */
 struct tune_params aarch64_tune_params = generic_tunings;
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 2f0777a37ac..84e6f79ca83 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -179,6 +179,8 @@ enum class aarch64_feature : unsigned char {
 
 /* Macros to test ISA flags.  */
 
+#define AARCH64_ISA_V8A		   (aarch64_isa_flags & AARCH64_FL_V8A)
+#define AARCH64_ISA_V8_1A	   (aarch64_isa_flags & AARCH64_FL_V8_1A)
 #define AARCH64_ISA_CRC            (aarch64_isa_flags & AARCH64_FL_CRC)
 #define AARCH64_ISA_CRYPTO         (aarch64_isa_flags & AARCH64_FL_CRYPTO)
 #define AARCH64_ISA_FP             (aarch64_isa_flags & AARCH64_FL_FP)
@@ -215,6 +217,8 @@ enum class aarch64_feature : unsigned char {
 #define AARCH64_ISA_SB		   (aarch64_isa_flags & AARCH64_FL_SB)
 #define AARCH64_ISA_V8R		   (aarch64_isa_flags & AARCH64_FL_V8R)
 #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_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)
@@ -223,6 +227,24 @@ enum class aarch64_feature : unsigned char {
 #define AARCH64_ISA_LS64	   (aarch64_isa_flags & AARCH64_FL_LS64)
 #define AARCH64_ISA_CSSC	   (aarch64_isa_flags & AARCH64_FL_CSSC)
 
+/* AARCH64_FL options necessary for system register implementation.  */
+
+/* Define AARCH64_FL aliases for architectural features which are protected
+   by -march flags in binutils but which receive no special treatment by GCC.
+
+   Such flags are inherited from the Binutils definition of system registers
+   and are mapped to the architecture in which the feature is implemented.  */
+#define AARCH64_FL_RAS		   AARCH64_FL_V8A
+#define AARCH64_FL_LOR		   AARCH64_FL_V8_1A
+#define AARCH64_FL_PAN		   AARCH64_FL_V8_1A
+#define AARCH64_FL_AMU		   AARCH64_FL_V8_4A
+#define AARCH64_FL_SCXTNUM	   AARCH64_FL_V8_5A
+#define AARCH64_FL_ID_PFR2	   AARCH64_FL_V8_5A
+
+/* Define AARCH64_FL aliases for features note yet implemented in GCC.
+   Accept them unconditionally.  */
+#define AARCH64_FL_SME		   0
+
 /* Crypto is an optional extension to AdvSIMD.  */
 #define TARGET_CRYPTO (AARCH64_ISA_CRYPTO)
 
-- 
2.41.0