Add fallback implementation for fixed_(u)int

src/typed-geometry/detail/intrinsics.hh

@@ -0,0 +1,61 @@
+#pragma once
+
+#include <clean-core/macros.hh>
+
+#ifdef _MSC_VER
+#include <intrin.h>
+#elif __has_include("x86intrin.h")
+#include <x86intrin.h>
+#include <cstring>
+#endif
+
+
+namespace tg::detail
+{
+CC_FORCE_INLINE char add_with_carry(char carry, unsigned long long a, unsigned long long b, unsigned long long* out)
+{
+#if defined(__x86_64__) || defined(_M_X64)
+    return _addcarry_u64(carry, a, b, out);
+#else
+#pragma message("[typed-geometry] Using fallback for add_with_carry(...). This may be slow!")
+    unsigned long long tmp = b + carry;
+    a += tmp;
+    *out = a;
+    return (tmp < carry) + (a < tmp);
+#endif
+}
+
+CC_FORCE_INLINE unsigned long long mul128(unsigned long long a, unsigned long long b, unsigned long long* high)
+{
+#if defined(_MSC_VER)
+    return _umul128(a, b, high);
+#elif __has_include("x86intrin.h")
+    return _mulx_u64(a, b, high);
+#elif defined(__SIZEOF_INT128__)
+    __uint128_t res = __uint128_t(a) * __uint128_t(b);
+    *high = res >> 64;
+    return static_cast<unsigned long long>(res);
+#else
+#pragma message("[typed-geometry] Using fallback for mul128(...). This may be slow!")
+    using u64 = unsigned long long;
+    using u32 = unsigned int;
+    static_assert(sizeof(u64) == 8, "u64 must be exactly 64 bits");
+    static_assert(sizeof(u32) == 4, "u32 must be exactly 32 bits");
+
+    u64 a_lo = u64(u32(a));
+    u64 a_hi = a >> 32;
+    u64 b_lo = u64(u32(b));
+    u64 b_hi = b >> 32;
+
+    u64 p0 = a_lo * b_lo;
+    u64 p1 = a_lo * b_hi;
+    u64 p2 = a_hi * b_lo;
+    u64 p3 = a_hi * b_hi;
+
+    u32 cy = u32(((p0 >> 32) + u32(p1) + u32(p2)) >> 32);
+
+    *high = p3 + (p1 >> 32) + (p2 >> 32) + cy;
+    return p0 + (p1 << 32) + (p2 << 32);
+#endif
+}
+}

src/typed-geometry/feature/fixed_int.hh

@@ -2,12 +2,6 @@
 
 #include <clean-core/macros.hh>
 
-#ifdef CC_COMPILER_MSVC
-#define TG_MUL_U128 _umul128
-#else
-#define TG_MUL_U128 _mulx_u64
-#endif
-
 #include <typed-geometry/functions/fixed_int/conversions.hh>
 #include <typed-geometry/functions/fixed_int/fixed_int.hh>
 #include <typed-geometry/functions/fixed_int/fixed_int_gen.hh>