[compiler-rt] [compiler-rt][RISCV] Implement __riscv_ifunc_select (PR #85790)

[Wang Pengcheng via llvm-commits]

================
@@ -0,0 +1,260 @@
+//=== ifunc_select.c - Check environment hardware feature -*- 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 BUFSIZE 1024
+
+static void fillzero(char *s, unsigned size) {
+  for (int i = 0; i < size; i++)
+    s[i] = '\0';
+}
+
+static unsigned strcmp(const char *a, const char *b) {
+  while (*a != '\0' && *b != '\0') {
+    if (*a != *b)
+      return 0;
+    a++;
+    b++;
+  }
+  if (*a == *b)
+    return 1;
+  return 0;
+}
+
+static void memcpy(char *dest, const char *src, unsigned len) {
+  for (unsigned i = 0; i < len; i++)
+    dest[i] = src[i];
+}
+
+static unsigned strlen(char *s) {
+  int len = 0;
+  while (*s != '\0') {
+    len++;
+    s++;
+  }
+  return len;
+}
+
+// TODO: Replace with more efficient algorithm
+static unsigned isPatternInSrc(char *src, char *pattern) {
+  char buf[BUFSIZE];
+  int lenOfSrc = strlen(src);
+  int lenOfPattern = strlen(pattern);
+  for (int i = 0; i + lenOfPattern < lenOfSrc; i++) {
+    fillzero(buf, BUFSIZE);
+    memcpy(buf, src + i, lenOfPattern);
+    if (strcmp(buf, pattern))
+      return 1;
+  }
+  return 0;
+}
+
+static char *tokenize(char *src, char *rst, char delim) {
+  while (*src != '\0' && *src != delim) {
+    *rst = *src;
+    src++;
+    rst++;
+  }
+  if (*src == delim)
+    src++;
+  return src;
+}
+
+static void getBasicExtFromHwFeatStr(char *rst, char *src) {
+  while (*src != 'r') {
+    src++;
+  }
+
+  while (*src != '_' && *src != '\0') {
+    *rst = *src;
+    rst++;
+    src++;
+  }
+}
+
+static unsigned checkFeatStrInHwFeatStr(char *FeatStr, char *HwFeatStr) {
+  // For basic extension like a,m,f,d...
+  if (strlen(FeatStr) == 1) {
+    char BasicExt[BUFSIZE];
+    fillzero(BasicExt, BUFSIZE);
+    getBasicExtFromHwFeatStr(BasicExt, HwFeatStr);
+    return isPatternInSrc(BasicExt, FeatStr);
+  }
+  // For zbb,zihintntl...
+  return isPatternInSrc(HwFeatStr, FeatStr);
+}
+
+#if defined(__linux__)
+
+#define SYS_read 63
+#define SYS_openat 56
+#define SYS_riscv_hwprobe 258
+
+static long syscall_impl_3_args(long number, long arg1, long arg2, long arg3) {
+  register long a7 __asm__("a7") = number;
+  register long a0 __asm__("a0") = arg1;
+  register long a1 __asm__("a1") = arg2;
+  register long a2 __asm__("a2") = arg3;
+  __asm__ __volatile__("ecall\n\t"
+                       : "=r"(a0)
+                       : "r"(a7), "r"(a0), "r"(a1), "r"(a2)
+                       : "memory");
+  return a0;
+}
+
+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;
+}
+
+static unsigned read(int fd, const void *buf, unsigned count) {
+  return syscall_impl_3_args(SYS_read, fd, (long)buf, count);
+}
+
+static int openat(int dirfd, const char *pathname, int flags) {
+  return syscall_impl_3_args(SYS_openat, (long)dirfd, (long)pathname, flags);
+}
+
+static void readUntilNextLine(int fd, char *rst, int len) {
+  char buf = '\0';
+  while (buf != '\n' && read(fd, &buf, 1) != 0 && len > 0) {
+    *rst = buf;
+    rst++;
+    len--;
+  }
+}
+
+static void __riscv_cpuinfo(char *FeatStr) {
+  char buf[BUFSIZE];
+  int fd = openat(0, "/proc/cpuinfo", 2);
+  do {
+    fillzero(buf, BUFSIZE);
+    readUntilNextLine(fd, buf, BUFSIZE);
+    if (isPatternInSrc(buf, "isa")) {
+      memcpy(FeatStr, buf, BUFSIZE);
+      return;
+    }
+  } while (strlen(buf) != 0);
+}
+
+struct riscv_hwprobe {
+  long long key;
+  unsigned long long value;
+};
+
+#define RISCV_HWPROBE_MAX_KEY 5
+#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 (1 << 0)
+#define RISCV_HWPROBE_KEY_IMA_EXT_0 4
+#define RISCV_HWPROBE_IMA_FD (1 << 0)
+#define RISCV_HWPROBE_IMA_C (1 << 1)
+#define RISCV_HWPROBE_IMA_V (1 << 2)
+#define RISCV_HWPROBE_EXT_ZBA (1 << 3)
+#define RISCV_HWPROBE_EXT_ZBB (1 << 4)
+#define RISCV_HWPROBE_EXT_ZBS (1 << 5)
+#define RISCV_HWPROBE_KEY_CPUPERF_0 5
+#define RISCV_HWPROBE_MISALIGNED_UNKNOWN (0 << 0)
+#define RISCV_HWPROBE_MISALIGNED_EMULATED (1 << 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)
+
----------------
wangpc-pp wrote:

Can we align to the newest interface: https://docs.kernel.org/arch/riscv/hwprobe.html?

https://github.com/llvm/llvm-project/pull/85790