[scudo] Add support for LoongArch hardware CRC32 checksumming

One has to probe for platform capability prior to use with HWCAP,
according to LoongArch documentation.

Author: xen0n

compiler-rt/lib/scudo/standalone/checksum.cpp

@@ -19,6 +19,8 @@
 #else
 #include <sys/auxv.h>
 #endif
+#elif defined(__loongarch__)
+#include <sys/auxv.h>
 #endif
 
 namespace scudo {
@@ -75,6 +77,15 @@ bool hasHardwareCRC32() {
   return !!(getauxval(AT_HWCAP) & HWCAP_CRC32);
 #endif // SCUDO_FUCHSIA
 }
+#elif defined(__loongarch__)
+// Query HWCAP for platform capability, according to *Software Development and
+// Build Convention for LoongArch Architectures* v0.1, Section 9.1.
+//
+// Link:
+// https://github.com/loongson/la-softdev-convention/blob/v0.1/la-softdev-convention.adoc#kernel-development
+bool hasHardwareCRC32() {
+  return !!(getauxval(AT_HWCAP) & HWCAP_LOONGARCH_CRC32);
+}
 #else
 // No hardware CRC32 implemented in Scudo for other architectures.
 bool hasHardwareCRC32() { return false; }

compiler-rt/lib/scudo/standalone/checksum.h

@@ -30,6 +30,10 @@
 #include <arm_acle.h>
 #define CRC32_INTRINSIC FIRST_32_SECOND_64(__crc32cw, __crc32cd)
 #endif
+#ifdef __loongarch__
+#include <larchintrin.h>
+#define CRC32_INTRINSIC FIRST_32_SECOND_64(__crcc_w_w_w, __crcc_w_d_w)
+#endif
 
 namespace scudo {
 

compiler-rt/lib/scudo/standalone/crc32_hw.cpp

@@ -17,4 +17,11 @@ u32 computeHardwareCRC32(u32 Crc, uptr Data) {
 #endif // defined(__CRC32__) || defined(__SSE4_2__) ||
        // defined(__ARM_FEATURE_CRC32)
 
+#if defined(__loongarch__)
+u32 computeHardwareCRC32(u32 Crc, uptr Data) {
+  // The LoongArch CRC intrinsics have the two input arguments swapped.
+  return static_cast<u32>(CRC32_INTRINSIC(Data, Crc));
+}
+#endif // defined(__loongarch__)
+
 } // namespace scudo