Replace __cpuid_check for AVX512 with compiler builtin cpu features (#655)

Replaces manual CPUID bit parsing in jvector_simd_check.c with
__builtin_cpu_supports and adds __builtin_cpu_init(). This corrects
missing XSAVE runtime checks, preventing #UD exceptions on systems where
512‑bit register state saves are disabled.

Author: r-devulap

jvector-native/src/main/c/jvector_simd.c

@@ -26,7 +26,7 @@ __m512i maskEighthBit;
 
 __attribute__((constructor))
 void initialize_constants() {
-    if (check_compatibility()) {
+    if (check_avx512_compatibility()) {
         initialIndexRegister = _mm512_setr_epi32(-16, -15, -14, -13, -12, -11, -10, -9,
                                              -8, -7, -6, -5, -4, -3, -2, -1);
         indexIncrement = _mm512_set1_epi32(16);

jvector-native/src/main/c/jvector_simd.h

@@ -20,7 +20,7 @@
 #define VECTOR_SIMD_DOT_H
 
 // check CPU support
-bool check_compatibility(void);
+bool check_avx512_compatibility(void);
 
 //F32
 float dot_product_f32(int preferred_size, const float* a, int aoffset, const float* b, int boffset, int length);

jvector-native/src/main/c/jvector_simd_check.c

@@ -17,21 +17,14 @@
 #include <cpuid.h>
 #include "jvector_simd.h"
 
-bool check_compatibility(void) {
-    unsigned int eax, ebx, ecx, edx;
-    bool avx512f_supported = false, avx512cd_supported = false,
-         avx512bw_supported = false, avx512dq_supported = false,
-         avx512vl_supported = false;
-
-    // Check for AVX-512 Foundation (AVX-512F) and other AVX-512 features:
-    // These are indicated by various bits of EBX from leaf 7, sub-leaf 0.
-    if (__get_cpuid_count(7, 0, &eax, &ebx, &ecx, &edx)) {
-        avx512f_supported = ebx & (1 << 16);     // AVX-512F
-        avx512cd_supported = ebx & (1 << 28);    // AVX-512CD
-        avx512bw_supported = ebx & (1 << 30);    // AVX-512BW
-        avx512dq_supported = ebx & (1 << 17);    // AVX-512DQ
-        avx512vl_supported = ebx & (1 << 31);    // AVX-512VL
-    }
-
-    return avx512f_supported && avx512cd_supported && avx512bw_supported && avx512dq_supported && avx512vl_supported;
-}
+bool check_avx512_compatibility(void) {
+    /* __builtin_cpu_init required when this is used in ifunc
+       resolver/__attribute__((constructor)) context, otherwise the CPU
+       features may not be detected correctly. */
+    __builtin_cpu_init();
+    return (__builtin_cpu_supports("avx512f") &&
+        __builtin_cpu_supports("avx512cd") &&
+        __builtin_cpu_supports("avx512dq") &&
+        __builtin_cpu_supports("avx512bw") &&
+        __builtin_cpu_supports("avx512vl"));
+}

jvector-native/src/main/java/io/github/jbellis/jvector/vector/NativeVectorizationProvider.java

@@ -35,7 +35,7 @@ public NativeVectorizationProvider() {
         if (!libraryLoaded) {
             throw new UnsupportedOperationException("Failed to load supporting native library.");
         }
-        if (!NativeSimdOps.check_compatibility()) {
+        if (!NativeSimdOps.check_avx512_compatibility()) {
             throw new UnsupportedOperationException("Native SIMD operations are not supported on this platform due to missing CPU support.");
         }
         this.vectorUtilSupport = new NativeVectorUtilSupport();

jvector-native/src/main/java/io/github/jbellis/jvector/vector/cnative/NativeSimdOps.java

@@ -96,55 +96,55 @@ public static int __bool_true_false_are_defined() {
         return __bool_true_false_are_defined;
     }
 
-    private static class check_compatibility {
+    private static class check_avx512_compatibility {
         public static final FunctionDescriptor DESC = FunctionDescriptor.of(
                 NativeSimdOps.C_BOOL    );
 
-        public static final MemorySegment ADDR = NativeSimdOps.findOrThrow("check_compatibility");
+        public static final MemorySegment ADDR = NativeSimdOps.findOrThrow("check_avx512_compatibility");
 
         public static final MethodHandle HANDLE = Linker.nativeLinker().downcallHandle(ADDR, DESC, Linker.Option.critical(true));
     }
 
     /**
      * Function descriptor for:
      * {@snippet lang=c :
-     * _Bool check_compatibility()
+     * _Bool check_avx512_compatibility()
      * }
      */
-    public static FunctionDescriptor check_compatibility$descriptor() {
-        return check_compatibility.DESC;
+    public static FunctionDescriptor check_avx512_compatibility$descriptor() {
+        return check_avx512_compatibility.DESC;
     }
 
     /**
      * Downcall method handle for:
      * {@snippet lang=c :
-     * _Bool check_compatibility()
+     * _Bool check_avx512_compatibility()
      * }
      */
-    public static MethodHandle check_compatibility$handle() {
-        return check_compatibility.HANDLE;
+    public static MethodHandle check_avx512_compatibility$handle() {
+        return check_avx512_compatibility.HANDLE;
     }
 
     /**
      * Address for:
      * {@snippet lang=c :
-     * _Bool check_compatibility()
+     * _Bool check_avx512_compatibility()
      * }
      */
-    public static MemorySegment check_compatibility$address() {
-        return check_compatibility.ADDR;
+    public static MemorySegment check_avx512_compatibility$address() {
+        return check_avx512_compatibility.ADDR;
     }
 
     /**
      * {@snippet lang=c :
-     * _Bool check_compatibility()
+     * _Bool check_avx512_compatibility()
      * }
      */
-    public static boolean check_compatibility() {
-        var mh$ = check_compatibility.HANDLE;
+    public static boolean check_avx512_compatibility() {
+        var mh$ = check_avx512_compatibility.HANDLE;
         try {
             if (TRACE_DOWNCALLS) {
-                traceDowncall("check_compatibility");
+                traceDowncall("check_avx512_compatibility");
             }
             return (boolean)mh$.invokeExact();
         } catch (Throwable ex$) {

jvector-native/src/test/java/io/github/jbellis/jvector/vector/cnative/NativeSimdOpsTest.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright DataStax, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.github.jbellis.jvector.vector.cnative;
+
+import org.junit.Assume;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class NativeSimdOpsTest {
+
+    /**
+     * Reads /proc/cpuinfo and returns true if all AVX-512 flags required by
+     * check_avx512_compatibility() are present: avx512f, avx512cd, avx512dq,
+     * avx512bw, avx512vl.
+     */
+    private static boolean cpuinfoReportsAvx512() throws IOException {
+        List<String> lines = Files.readAllLines(Path.of("/proc/cpuinfo"));
+        List<String> required = List.of("avx512f", "avx512cd", "avx512dq", "avx512bw", "avx512vl");
+        for (String line : lines) {
+            if (line.startsWith("flags")) {
+                String[] flags = line.split("\\s+");
+                List<String> flagList = List.of(flags);
+                return flagList.containsAll(required);
+            }
+        }
+        return false;
+    }
+
+    @Test
+    public void testCheckAvx512CompatibilityMatchesCpuinfo() throws IOException {
+        boolean libraryLoaded = LibraryLoader.loadJvector();
+        Assume.assumeTrue("Native jvector library not available; skipping AVX-512 check", libraryLoaded);
+
+        boolean expectedFromCpuinfo = cpuinfoReportsAvx512();
+        boolean actualFromNative = NativeSimdOps.check_avx512_compatibility();
+
+        assertEquals(
+                "check_avx512_compatibility() should match AVX-512 flag presence in /proc/cpuinfo",
+                expectedFromCpuinfo,
+                actualFromNative);
+    }
+}