8172232: SPARC ISA/CPU feature detection is broken/insufficient (on Linux)

Reimplementation extending feature detection to SPARC Core C3&C4.

Reviewed-by: kvn, neliasso

src/hotspot/os_cpu/linux_sparc/vm_version_linux_sparc.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2017, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -27,58 +27,326 @@
 #include "runtime/os.hpp"
 #include "vm_version_sparc.hpp"
 
-static bool cpuinfo_field_contains(const char* field, const char* value) {
-  char line[1024];
-  bool rv = false;
 
-  FILE* fp = fopen("/proc/cpuinfo", "r");
-  if (fp == NULL) {
-    return rv;
-  }
+#define CPUINFO_LINE_SIZE 1024
 
-  while (fgets(line, sizeof(line), fp) != NULL) {
-    assert(strlen(line) < sizeof(line) - 1, "buffer line[1024] is too small.");
-    if (strncmp(line, field, strlen(field)) == 0) {
-      if (strstr(line, value) != NULL) {
-        rv = true;
+
+class CPUinfo {
+public:
+  CPUinfo(const char* field) : _string(NULL) {
+
+    char line[CPUINFO_LINE_SIZE];
+    FILE* fp = fopen("/proc/cpuinfo", "r");
+
+    if (fp != NULL) {
+      while (fgets(line, sizeof(line), fp) != NULL) {
+        assert(strlen(line) < sizeof(line) - 1,
+               "buffer too small (%d)", CPUINFO_LINE_SIZE);
+
+        const char* vstr = match_field(line, field);
+
+        if (vstr != NULL) {
+          // We have a matching line and a valid starting point to the value of
+          // the field, copy the string for keeps.
+          _string = strdup(vstr);
+          break;
+        }
       }
-      break;
+      fclose(fp);
     }
   }
 
-  fclose(fp);
-  return rv;
-}
+  ~CPUinfo() { os::free((void*)_string); }
 
-static bool detect_niagara() {
-  return cpuinfo_field_contains("cpu", "Niagara");
-}
+  const char* value() const { return _string; }
 
-static bool detect_M_family() {
-  return cpuinfo_field_contains("cpu", "SPARC-M");
-}
+  bool valid() const { return _string != NULL; }
 
-static bool detect_blkinit() {
-  return cpuinfo_field_contains("cpucaps", "blkinit");
-}
-
-int VM_Version::platform_features(int features) {
-  // Default to generic v9
-  features = generic_v9_m;
-
-  if (detect_niagara()) {
-    log_info(os, cpu)("Detected Linux on Niagara");
-    features = niagara1_m | T_family_m;
+  bool match(const char* s) const {
+    return valid() ? strcmp(_string, s) == 0 : false;
   }
 
-  if (detect_M_family()) {
-    log_info(os, cpu)("Detected Linux on M family");
-    features = sun4v_m | generic_v9_m | M_family_m | T_family_m;
-  }
+private:
+  const char* _string;
 
-  if (detect_blkinit()) {
-    features |= blk_init_instructions_m;
-  }
+  const char* match_field(char line[CPUINFO_LINE_SIZE], const char* field);
+  const char* match_alo(const char* text, const char* exp);
+  const char* match_seq(const char* text, const char* seq);
+};
 
-  return features;
+/* Given a line of text read from /proc/cpuinfo, determine if the property header
+ * matches the field specified, according to the following regexp: "<field>"\W+:\W+
+ *
+ * If we have a matching expression, return a pointer to the first character after
+ * the matching pattern, i.e. the "value", otherwise return NULL.
+ */
+const char* CPUinfo::match_field(char line[CPUINFO_LINE_SIZE], const char* field) {
+  return match_alo(match_seq(match_alo(match_seq(line, field), "\t "), ":"), "\t ");
+}
+
+/* Match a sequence of at-least-one character in the string expression (exp) to
+ * the text input.
+ */
+const char* CPUinfo::match_alo(const char* text, const char* exp) {
+  if (text == NULL) return NULL;
+
+  const char* chp;
+
+  for (chp = &text[0]; *chp != '\0'; chp++) {
+    if (strchr(exp, *chp) == NULL) break;
+  }
+
+  return text < chp ? chp : NULL;
+}
+
+/* Match an exact sequence of characters as specified by the string expression
+ * (seq) to the text input.
+ */
+const char* CPUinfo::match_seq(const char* text, const char* seq) {
+  if (text == NULL) return NULL;
+
+  while (*seq != '\0') {
+    if (*seq != *text++) break; else seq++;
+  }
+
+  return *seq == '\0' ? text : NULL;
+}
+
+
+typedef struct {
+  const uint32_t    hash;
+  bool              seen;
+  const char* const name;
+  const uint64_t    mask;
+} FeatureEntry;
+
+
+static uint64_t parse_features(FeatureEntry feature_tbl[], const char input[]);
+
+
+void VM_Version::platform_features() {
+
+  // Some of the features reported via "cpucaps", such as; 'flush', 'stbar',
+  // 'swap', 'muldiv', 'ultra3', 'blkinit', 'n2', 'mul32', 'div32', 'fsmuld'
+  // and 'v8plus', are either SPARC V8, supported by all HW or simply nonsense
+  // (the 'ultra3' "property").
+  //
+  // Entries marked as 'NYI' are not yet supported via "cpucaps" but are
+  // expected to have the names used in the table below (these are SPARC M7
+  // features or more recent).
+  //
+  // NOTE: Table sorted on lookup/hash ID.
+
+  static FeatureEntry s_feature_tbl[] = {
+    { 0x006f, false, "v9",         ISA_v9_msk },            // Mandatory
+    { 0x00a6, false, "md5",        ISA_md5_msk },
+    { 0x00ce, false, "adi",        ISA_adi_msk },           // NYI
+    { 0x00d7, false, "ima",        ISA_ima_msk },
+    { 0x00d9, false, "aes",        ISA_aes_msk },
+    { 0x00db, false, "hpc",        ISA_hpc_msk },
+    { 0x00dc, false, "des",        ISA_des_msk },
+    { 0x00ed, false, "sha1",       ISA_sha1_msk },
+    { 0x00f2, false, "vis",        ISA_vis1_msk },
+    { 0x0104, false, "vis2",       ISA_vis2_msk },
+    { 0x0105, false, "vis3",       ISA_vis3_msk },
+    { 0x0114, false, "sha512",     ISA_sha512_msk },
+    { 0x0119, false, "sha256",     ISA_sha256_msk },
+    { 0x011a, false, "fmaf",       ISA_fmaf_msk },
+    { 0x0132, false, "popc",       ISA_popc_msk },
+    { 0x0140, false, "crc32c",     ISA_crc32c_msk },
+    { 0x0147, false, "vis3b",      ISA_vis3b_msk },         // NYI
+    { 0x017e, false, "pause",      ISA_pause_msk },
+    { 0x0182, false, "mwait",      ISA_mwait_msk },         // NYI
+    { 0x018b, false, "mpmul",      ISA_mpmul_msk },
+    { 0x018e, false, "sparc5",     ISA_sparc5_msk },        // NYI
+    { 0x01a9, false, "cbcond",     ISA_cbcond_msk },
+    { 0x01c3, false, "vamask",     ISA_vamask_msk },        // NYI
+    { 0x01ca, false, "kasumi",     ISA_kasumi_msk },
+    { 0x01e3, false, "xmpmul",     ISA_xmpmul_msk },        // NYI
+    { 0x022c, false, "montmul",    ISA_mont_msk },
+    { 0x0234, false, "montsqr",    ISA_mont_msk },
+    { 0x0238, false, "camellia",   ISA_camellia_msk },
+    { 0x024a, false, "ASIBlkInit", ISA_blk_init_msk },
+    { 0x0284, false, "xmontmul",   ISA_xmont_msk },         // NYI
+    { 0x02e6, false, "pause_nsec", ISA_pause_nsec_msk },    // NYI
+
+    { 0x0000, false, NULL, 0 }
+  };
+
+  CPUinfo caps("cpucaps");      // Read "cpucaps" from /proc/cpuinfo.
+
+  assert(caps.valid(), "must be");
+
+  _features = parse_features(s_feature_tbl, caps.value());
+
+  assert(has_v9(), "must be");  // Basic SPARC-V9 required (V8 not supported).
+
+  CPUinfo type("type");
+
+  bool is_sun4v = type.match("sun4v");   // All Oracle SPARC + Fujitsu Athena+
+  bool is_sun4u = type.match("sun4u");   // All other Fujitsu
+
+  uint64_t synthetic = 0;
+
+  if (is_sun4v) {
+    // Indirect and direct branches are equally fast.
+    synthetic = CPU_fast_ind_br_msk;
+    // Fast IDIV, BIS and LD available on Niagara Plus.
+    if (has_vis2()) {
+      synthetic |= (CPU_fast_idiv_msk | CPU_fast_ld_msk);
+      // ...on Core C4 however, we prefer not to use BIS.
+      if (!has_sparc5()) {
+        synthetic |= CPU_fast_bis_msk;
+      }
+    }
+    // Niagara Core C3 supports fast RDPC and block zeroing.
+    if (has_ima()) {
+      synthetic |= (CPU_fast_rdpc_msk | CPU_blk_zeroing_msk);
+    }
+    // Niagara Core C3 and C4 have slow CMOVE.
+    if (!has_ima()) {
+      synthetic |= CPU_fast_cmove_msk;
+    }
+  } else if (is_sun4u) {
+    // SPARC64 only have fast IDIV and RDPC.
+    synthetic |= (CPU_fast_idiv_msk | CPU_fast_rdpc_msk);
+  } else {
+    log_info(os, cpu)("Unable to derive CPU features: %s", type.value());
+  }
+
+  _features += synthetic;   // Including CPU derived/synthetic features.
+}
+
+
+////////////////////////////////////////////////////////////////////////////////
+
+static uint32_t uhash32(const char name[]);
+
+static void update_table(FeatureEntry feature_tbl[], uint32_t hv,
+                         const char* ch1p,
+                         const char* endp);
+
+/* Given a feature table, parse the input text holding the string value of
+ * 'cpucaps' as reported by '/proc/cpuinfo', in order to complete the table
+ * with information on each admissible feature (whether present or not).
+ *
+ * Return the composite bit-mask representing the features found.
+ */
+static uint64_t parse_features(FeatureEntry feature_tbl[], const char input[]) {
+  log_info(os, cpu)("Parse CPU features: %s\n", input);
+
+#ifdef ASSERT
+  // Verify that hash value entries in the table are unique and ordered.
+
+  uint32_t prev = 0;
+
+  for (uint k = 0; feature_tbl[k].name != NULL; k++) {
+    feature_tbl[k].seen = false;
+
+    assert(feature_tbl[k].hash == uhash32(feature_tbl[k].name),
+           "feature '%s' has mismatching hash 0x%08x (expected 0x%08x).\n",
+           feature_tbl[k].name,
+           feature_tbl[k].hash,
+           uhash32(feature_tbl[k].name));
+
+    assert(prev < feature_tbl[k].hash,
+           "feature '%s' has invalid hash 0x%08x (previous is 0x%08x).\n",
+           feature_tbl[k].name,
+           feature_tbl[k].hash,
+           prev);
+
+    prev = feature_tbl[k].hash;
+  }
+#endif
+  // Identify features from the input, consisting of a string with features
+  // separated by commas (or whitespace), e.g. "flush,muldiv,v9,mul32,div32,
+  // v8plus,popc,vis".
+
+  uint32_t hv = 0;
+  const char* ch1p = &input[0];
+  uint i = 0;
+
+  do {
+    char ch = input[i];
+
+    if (isalnum(ch) || ch == '_') {
+      hv += (ch - 32u);
+    }
+    else if (isspace(ch) || ch == ',' || ch == '\0') { // end-of-token
+      if (ch1p < &input[i]) {
+        update_table(feature_tbl, hv, ch1p, &input[i]);
+      }
+      ch1p = &input[i + 1]; hv = 0;
+    } else {
+      // Handle non-accepted input robustly.
+      log_info(os, cpu)("Bad token in feature string: '%c' (0x%02x).\n", ch, ch);
+      ch1p = &input[i + 1]; hv = 0;
+    }
+  }
+  while (input[i++] != '\0');
+
+  // Compute actual bit-mask representation.
+
+  uint64_t mask = 0;
+
+  for (uint k = 0; feature_tbl[k].name != NULL; k++) {
+    mask |= feature_tbl[k].seen ? feature_tbl[k].mask : 0;
+  }
+
+  return mask;
+}
+
+static uint32_t uhash32(const char name[]) {
+  uint32_t hv = 0;
+
+  for (uint i = 0; name[i] != '\0'; i++) {
+    hv += (name[i] - 32u);
+  }
+
+  return hv;
+}
+
+static bool verify_match(const char name[], const char* ch1p, const char* endp);
+
+static void update_table(FeatureEntry feature_tbl[], uint32_t hv, const char* ch1p, const char* endp) {
+  assert(ch1p < endp, "at least one character");
+
+  // Look for a hash value in the table. Since this table is a small one (and
+  // is expected to stay small), we use a simple linear search (iff the table
+  // grows large, we may consider to adopt a binary ditto, or a perfect hash).
+
+  for (uint k = 0; feature_tbl[k].name != NULL; k++) {
+    uint32_t hash = feature_tbl[k].hash;
+
+    if (hash < hv) continue;
+
+    if (hash == hv) {
+      const char* name = feature_tbl[k].name;
+
+      if (verify_match(name, ch1p, endp)) {
+        feature_tbl[k].seen = true;
+        break;
+      }
+    }
+
+    // Either a non-matching feature (when hash == hv) or hash > hv. In either
+    // case we break out of the loop and terminate the search (note that the
+    // table is assumed to be uniquely sorted on the hash).
+
+    break;
+  }
+}
+
+static bool verify_match(const char name[], const char* ch1p, const char* endp) {
+  size_t len = strlen(name);
+
+  if (len != static_cast<size_t>(endp - ch1p)) {
+    return false;
+  }
+
+  for (uint i = 0; ch1p + i < endp; i++) {
+    if (name[i] != ch1p[i]) return false;
+  }
+
+  return true;
 }