Squashed 'externals/biscuit/' content from commit 1d53c9e6

git-subtree-dir: externals/biscuit
git-subtree-split: 1d53c9e6cfe56544982200a5bac15a5de064936b

include/biscuit/cpuinfo.hpp

@@ -0,0 +1,101 @@
+// Copyright (c), 2022, KNS Group LLC (YADRO)
+//
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+#pragma once
+
+#include <biscuit/assembler.hpp>
+#include <biscuit/registers.hpp>
+#include <cstddef>
+#include <cstdint>
+
+#if defined(__linux__) && defined(__riscv)
+#include <sys/auxv.h>
+#include <sys/prctl.h>
+#include <asm/hwcap.h>
+#endif
+
+namespace biscuit {
+
+#ifndef COMPAT_HWCAP_ISA_I
+#define COMPAT_HWCAP_ISA_I  (1U << ('I' - 'A'))
+#endif
+
+#ifndef COMPAT_HWCAP_ISA_M
+#define COMPAT_HWCAP_ISA_M  (1U << ('M' - 'A'))
+#endif
+
+#ifndef COMPAT_HWCAP_ISA_A
+#define COMPAT_HWCAP_ISA_A  (1U << ('A' - 'A'))
+#endif
+
+#ifndef COMPAT_HWCAP_ISA_F
+#define COMPAT_HWCAP_ISA_F  (1U << ('F' - 'A'))
+#endif
+
+#ifndef COMPAT_HWCAP_ISA_D
+#define COMPAT_HWCAP_ISA_D  (1U << ('D' - 'A'))
+#endif
+
+#ifndef COMPAT_HWCAP_ISA_C
+#define COMPAT_HWCAP_ISA_C  (1U << ('C' - 'A'))
+#endif
+
+#ifndef COMPAT_HWCAP_ISA_V
+#define COMPAT_HWCAP_ISA_V  (1U << ('V' - 'A'))
+#endif
+
+enum class RISCVExtension : uint64_t {
+    I = COMPAT_HWCAP_ISA_I,
+    M = COMPAT_HWCAP_ISA_M,
+    A = COMPAT_HWCAP_ISA_A,
+    F = COMPAT_HWCAP_ISA_F,
+    D = COMPAT_HWCAP_ISA_D,
+    C = COMPAT_HWCAP_ISA_C,
+    V = COMPAT_HWCAP_ISA_V
+};
+
+template <CSR csr>
+struct CSRReader : public biscuit::Assembler {
+    // Buffer capacity exactly for 2 instructions.
+    static constexpr size_t capacity = 8;
+
+    CSRReader() : biscuit::Assembler{CSRReader::capacity} {
+        CSRR(a0, csr);
+        RET();
+    }
+
+    // Copy constructor and assignment.
+    CSRReader(const CSRReader&) = delete;
+    CSRReader& operator=(const CSRReader&) = delete;
+
+    // Move constructor and assignment.
+    CSRReader(CSRReader&&) = default;
+    CSRReader& operator=(CSRReader&&) = default;
+
+    template <typename CSRReaderFunc>
+    CSRReaderFunc GetCode() {
+        this->GetCodeBuffer().SetExecutable();
+        return reinterpret_cast<CSRReaderFunc>(this->GetBufferPointer(0));
+    }
+};
+
+/**
+ * Class that detects information about a RISC-V CPU.
+ */
+class CPUInfo {
+public:
+    /**
+     * Checks if a particular RISC-V extension is available.
+     *
+     * @param extension The extension to check.
+     */
+    bool Has(RISCVExtension extension) const;
+
+    /// Returns the vector register length in bytes.
+    uint32_t GetVlenb() const;
+};
+
+} // namespace biscuit