[compiler-rt][RISCV] Implement __init_riscv_feature_bits (#85790)

Base on riscv-non-isa/riscv-c-api-doc#74, this
patch defines the `__riscv_feature_bits` and
`__riscv_vendor_feature_bits` structures to store the enabled feature
bits at runtime.

It also introduces the `__init_riscv_feature_bits` function to update
these structures based on the platform query mechanism.

Additionally, the groupid/bitmask definitions from
riscv-non-isa/riscv-c-api-doc#74 are declared
and used to update the `__riscv_feature_bits` and
`__riscv_vendor_feature_bits` structures.

---------

Co-authored-by: Kito Cheng <[email protected]>

Author: BeMg

compiler-rt/lib/builtins/CMakeLists.txt

@@ -739,6 +739,7 @@ endif()
 set(powerpc64le_SOURCES ${powerpc64_SOURCES})
 
 set(riscv_SOURCES
+  riscv/feature_bits.c
   riscv/fp_mode.c
   riscv/save.S
   riscv/restore.S

compiler-rt/lib/builtins/riscv/feature_bits.c

@@ -0,0 +1,298 @@
+//=== feature_bits.c - Update RISC-V Feature Bits Structure -*- C -*-=========//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#define RISCV_FEATURE_BITS_LENGTH 1
+struct {
+  unsigned length;
+  unsigned long long features[RISCV_FEATURE_BITS_LENGTH];
+} __riscv_feature_bits __attribute__((visibility("hidden"), nocommon));
+
+#define RISCV_VENDOR_FEATURE_BITS_LENGTH 1
+struct {
+  unsigned vendorID;
+  unsigned length;
+  unsigned long long features[RISCV_VENDOR_FEATURE_BITS_LENGTH];
+} __riscv_vendor_feature_bits __attribute__((visibility("hidden"), nocommon));
+
+// NOTE: Should sync-up with RISCVFeatures.td
+// TODO: Maybe generate a header from tablegen then include it.
+#define A_GROUPID 0
+#define A_BITMASK (1ULL << 0)
+#define C_GROUPID 0
+#define C_BITMASK (1ULL << 2)
+#define D_GROUPID 0
+#define D_BITMASK (1ULL << 3)
+#define F_GROUPID 0
+#define F_BITMASK (1ULL << 5)
+#define I_GROUPID 0
+#define I_BITMASK (1ULL << 8)
+#define M_GROUPID 0
+#define M_BITMASK (1ULL << 12)
+#define V_GROUPID 0
+#define V_BITMASK (1ULL << 21)
+#define ZACAS_GROUPID 0
+#define ZACAS_BITMASK (1ULL << 26)
+#define ZBA_GROUPID 0
+#define ZBA_BITMASK (1ULL << 27)
+#define ZBB_GROUPID 0
+#define ZBB_BITMASK (1ULL << 28)
+#define ZBC_GROUPID 0
+#define ZBC_BITMASK (1ULL << 29)
+#define ZBKB_GROUPID 0
+#define ZBKB_BITMASK (1ULL << 30)
+#define ZBKC_GROUPID 0
+#define ZBKC_BITMASK (1ULL << 31)
+#define ZBKX_GROUPID 0
+#define ZBKX_BITMASK (1ULL << 32)
+#define ZBS_GROUPID 0
+#define ZBS_BITMASK (1ULL << 33)
+#define ZFA_GROUPID 0
+#define ZFA_BITMASK (1ULL << 34)
+#define ZFH_GROUPID 0
+#define ZFH_BITMASK (1ULL << 35)
+#define ZFHMIN_GROUPID 0
+#define ZFHMIN_BITMASK (1ULL << 36)
+#define ZICBOZ_GROUPID 0
+#define ZICBOZ_BITMASK (1ULL << 37)
+#define ZICOND_GROUPID 0
+#define ZICOND_BITMASK (1ULL << 38)
+#define ZIHINTNTL_GROUPID 0
+#define ZIHINTNTL_BITMASK (1ULL << 39)
+#define ZIHINTPAUSE_GROUPID 0
+#define ZIHINTPAUSE_BITMASK (1ULL << 40)
+#define ZKND_GROUPID 0
+#define ZKND_BITMASK (1ULL << 41)
+#define ZKNE_GROUPID 0
+#define ZKNE_BITMASK (1ULL << 42)
+#define ZKNH_GROUPID 0
+#define ZKNH_BITMASK (1ULL << 43)
+#define ZKSED_GROUPID 0
+#define ZKSED_BITMASK (1ULL << 44)
+#define ZKSH_GROUPID 0
+#define ZKSH_BITMASK (1ULL << 45)
+#define ZKT_GROUPID 0
+#define ZKT_BITMASK (1ULL << 46)
+#define ZTSO_GROUPID 0
+#define ZTSO_BITMASK (1ULL << 47)
+#define ZVBB_GROUPID 0
+#define ZVBB_BITMASK (1ULL << 48)
+#define ZVBC_GROUPID 0
+#define ZVBC_BITMASK (1ULL << 49)
+#define ZVFH_GROUPID 0
+#define ZVFH_BITMASK (1ULL << 50)
+#define ZVFHMIN_GROUPID 0
+#define ZVFHMIN_BITMASK (1ULL << 51)
+#define ZVKB_GROUPID 0
+#define ZVKB_BITMASK (1ULL << 52)
+#define ZVKG_GROUPID 0
+#define ZVKG_BITMASK (1ULL << 53)
+#define ZVKNED_GROUPID 0
+#define ZVKNED_BITMASK (1ULL << 54)
+#define ZVKNHA_GROUPID 0
+#define ZVKNHA_BITMASK (1ULL << 55)
+#define ZVKNHB_GROUPID 0
+#define ZVKNHB_BITMASK (1ULL << 56)
+#define ZVKSED_GROUPID 0
+#define ZVKSED_BITMASK (1ULL << 57)
+#define ZVKSH_GROUPID 0
+#define ZVKSH_BITMASK (1ULL << 58)
+#define ZVKT_GROUPID 0
+#define ZVKT_BITMASK (1ULL << 59)
+
+#if defined(__linux__)
+
+static long syscall_impl_5_args(long number, long arg1, long arg2, long arg3,
+                                long arg4, long arg5) {
+  register long a7 __asm__("a7") = number;
+  register long a0 __asm__("a0") = arg1;
+  register long a1 __asm__("a1") = arg2;
+  register long a2 __asm__("a2") = arg3;
+  register long a3 __asm__("a3") = arg4;
+  register long a4 __asm__("a4") = arg5;
+  __asm__ __volatile__("ecall\n\t"
+                       : "=r"(a0)
+                       : "r"(a7), "r"(a0), "r"(a1), "r"(a2), "r"(a3), "r"(a4)
+                       : "memory");
+  return a0;
+}
+
+#define RISCV_HWPROBE_KEY_MVENDORID 0
+#define RISCV_HWPROBE_KEY_MARCHID 1
+#define RISCV_HWPROBE_KEY_MIMPID 2
+#define RISCV_HWPROBE_KEY_BASE_BEHAVIOR 3
+#define RISCV_HWPROBE_BASE_BEHAVIOR_IMA (1ULL << 0)
+#define RISCV_HWPROBE_KEY_IMA_EXT_0 4
+#define RISCV_HWPROBE_IMA_FD (1ULL << 0)
+#define RISCV_HWPROBE_IMA_C (1ULL << 1)
+#define RISCV_HWPROBE_IMA_V (1ULL << 2)
+#define RISCV_HWPROBE_EXT_ZBA (1ULL << 3)
+#define RISCV_HWPROBE_EXT_ZBB (1ULL << 4)
+#define RISCV_HWPROBE_EXT_ZBS (1ULL << 5)
+#define RISCV_HWPROBE_EXT_ZICBOZ (1ULL << 6)
+#define RISCV_HWPROBE_EXT_ZBC (1ULL << 7)
+#define RISCV_HWPROBE_EXT_ZBKB (1ULL << 8)
+#define RISCV_HWPROBE_EXT_ZBKC (1ULL << 9)
+#define RISCV_HWPROBE_EXT_ZBKX (1ULL << 10)
+#define RISCV_HWPROBE_EXT_ZKND (1ULL << 11)
+#define RISCV_HWPROBE_EXT_ZKNE (1ULL << 12)
+#define RISCV_HWPROBE_EXT_ZKNH (1ULL << 13)
+#define RISCV_HWPROBE_EXT_ZKSED (1ULL << 14)
+#define RISCV_HWPROBE_EXT_ZKSH (1ULL << 15)
+#define RISCV_HWPROBE_EXT_ZKT (1ULL << 16)
+#define RISCV_HWPROBE_EXT_ZVBB (1ULL << 17)
+#define RISCV_HWPROBE_EXT_ZVBC (1ULL << 18)
+#define RISCV_HWPROBE_EXT_ZVKB (1ULL << 19)
+#define RISCV_HWPROBE_EXT_ZVKG (1ULL << 20)
+#define RISCV_HWPROBE_EXT_ZVKNED (1ULL << 21)
+#define RISCV_HWPROBE_EXT_ZVKNHA (1ULL << 22)
+#define RISCV_HWPROBE_EXT_ZVKNHB (1ULL << 23)
+#define RISCV_HWPROBE_EXT_ZVKSED (1ULL << 24)
+#define RISCV_HWPROBE_EXT_ZVKSH (1ULL << 25)
+#define RISCV_HWPROBE_EXT_ZVKT (1ULL << 26)
+#define RISCV_HWPROBE_EXT_ZFH (1ULL << 27)
+#define RISCV_HWPROBE_EXT_ZFHMIN (1ULL << 28)
+#define RISCV_HWPROBE_EXT_ZIHINTNTL (1ULL << 29)
+#define RISCV_HWPROBE_EXT_ZVFH (1ULL << 30)
+#define RISCV_HWPROBE_EXT_ZVFHMIN (1ULL << 31)
+#define RISCV_HWPROBE_EXT_ZFA (1ULL << 32)
+#define RISCV_HWPROBE_EXT_ZTSO (1ULL << 33)
+#define RISCV_HWPROBE_EXT_ZACAS (1ULL << 34)
+#define RISCV_HWPROBE_EXT_ZICOND (1ULL << 35)
+#define RISCV_HWPROBE_EXT_ZIHINTPAUSE (1ULL << 36)
+#define RISCV_HWPROBE_KEY_CPUPERF_0 5
+#define RISCV_HWPROBE_MISALIGNED_UNKNOWN (0 << 0)
+#define RISCV_HWPROBE_MISALIGNED_EMULATED (1ULL << 0)
+#define RISCV_HWPROBE_MISALIGNED_SLOW (2 << 0)
+#define RISCV_HWPROBE_MISALIGNED_FAST (3 << 0)
+#define RISCV_HWPROBE_MISALIGNED_UNSUPPORTED (4 << 0)
+#define RISCV_HWPROBE_MISALIGNED_MASK (7 << 0)
+#define RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE 6
+/* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
+
+struct riscv_hwprobe {
+  long long key;
+  unsigned long long value;
+};
+
+#define __NR_riscv_hwprobe 258
+static long initHwProbe(struct riscv_hwprobe *Hwprobes, int len) {
+  return syscall_impl_5_args(__NR_riscv_hwprobe, (long)Hwprobes, len, 0, 0, 0);
+}
+
+#define SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(EXTNAME)                    \
+  SET_SINGLE_IMAEXT_RISCV_FEATURE(RISCV_HWPROBE_EXT_##EXTNAME, EXTNAME)
+
+#define SET_SINGLE_IMAEXT_RISCV_FEATURE(HWPROBE_BITMASK, EXT)                  \
+  SET_SINGLE_RISCV_FEATURE(IMAEXT0Value &HWPROBE_BITMASK, EXT)
+
+#define SET_SINGLE_RISCV_FEATURE(COND, EXT)                                    \
+  if (COND) {                                                                  \
+    SET_RISCV_FEATURE(EXT);                                                    \
+  }
+
+#define SET_RISCV_FEATURE(EXT) features[EXT##_GROUPID] |= EXT##_BITMASK
+
+static void initRISCVFeature(struct riscv_hwprobe Hwprobes[]) {
+
+  // Note: If a hwprobe key is unknown to the kernel, its key field
+  // will be cleared to -1, and its value set to 0.
+  // This unsets all extension bitmask bits.
+
+  // Init vendor extension
+  __riscv_vendor_feature_bits.length = 0;
+  __riscv_vendor_feature_bits.vendorID = Hwprobes[2].value;
+
+  // Init standard extension
+  // TODO: Maybe Extension implied generate from tablegen?
+  __riscv_feature_bits.length = RISCV_FEATURE_BITS_LENGTH;
+
+  unsigned long long features[RISCV_FEATURE_BITS_LENGTH];
+  int i;
+
+  for (i = 0; i < RISCV_FEATURE_BITS_LENGTH; i++)
+    features[i] = 0;
+
+  // Check RISCV_HWPROBE_KEY_BASE_BEHAVIOR
+  unsigned long long BaseValue = Hwprobes[0].value;
+  if (BaseValue & RISCV_HWPROBE_BASE_BEHAVIOR_IMA) {
+    SET_RISCV_FEATURE(I);
+    SET_RISCV_FEATURE(M);
+    SET_RISCV_FEATURE(A);
+  }
+
+  // Check RISCV_HWPROBE_KEY_IMA_EXT_0
+  unsigned long long IMAEXT0Value = Hwprobes[1].value;
+  if (IMAEXT0Value & RISCV_HWPROBE_IMA_FD) {
+    SET_RISCV_FEATURE(F);
+    SET_RISCV_FEATURE(D);
+  }
+
+  SET_SINGLE_IMAEXT_RISCV_FEATURE(RISCV_HWPROBE_IMA_C, C);
+  SET_SINGLE_IMAEXT_RISCV_FEATURE(RISCV_HWPROBE_IMA_V, V);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZBA);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZBB);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZBS);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZICBOZ);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZBC);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZBKB);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZBKC);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZBKX);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZKND);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZKNE);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZKNH);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZKSED);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZKSH);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZKT);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVBB);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVBC);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVKB);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVKG);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVKNED);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVKNHA);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVKNHB);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVKSED);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVKSH);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVKT);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZFH);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZFHMIN);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZIHINTNTL);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZIHINTPAUSE);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVFH);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZVFHMIN);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZFA);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZTSO);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZACAS);
+  SET_RISCV_HWPROBE_EXT_SINGLE_RISCV_FEATURE(ZICOND);
+
+  for (i = 0; i < RISCV_FEATURE_BITS_LENGTH; i++)
+    __riscv_feature_bits.features[i] = features[i];
+}
+
+#endif // defined(__linux__)
+
+static int FeaturesBitCached = 0;
+
+void __init_riscv_feature_bits() {
+
+  if (FeaturesBitCached)
+    return;
+
+#if defined(__linux__)
+  struct riscv_hwprobe Hwprobes[] = {
+      {RISCV_HWPROBE_KEY_BASE_BEHAVIOR, 0},
+      {RISCV_HWPROBE_KEY_IMA_EXT_0, 0},
+      {RISCV_HWPROBE_KEY_MVENDORID, 0},
+  };
+  if (initHwProbe(Hwprobes, sizeof(Hwprobes) / sizeof(Hwprobes[0])))
+    return;
+
+  initRISCVFeature(Hwprobes);
+#endif // defined(__linux__)
+
+  FeaturesBitCached = 1;
+}