remove libgcc dep

core/lib/meson.build

@@ -1,6 +1,7 @@
 # Freestanding libc functions that are needed in the kernel
 
 kernel_sources += files(
+    'runtime.c',
     'stdlib.c',
     'string.c',
 )

core/lib/runtime.c

@@ -0,0 +1,94 @@
+// Compiler runtime support like libgcc or compiler-rt.
+// Extend as required.
+
+#include <stdint.h>
+
+uint64_t __udivdi3(uint64_t dividend, uint64_t divisor) {
+    if (divisor == 0)
+        return 0;
+
+    if (dividend < divisor)
+        return 0;
+
+    unsigned shift = __builtin_clzll(divisor) - __builtin_clzll(dividend);
+
+    divisor <<= shift;
+
+    uint64_t quotient = 0;
+
+    for (;;) {
+        if (dividend >= divisor) {
+            dividend -= divisor;
+            quotient |= (uint64_t)1 << shift;
+        }
+
+        if (shift == 0)
+            break;
+
+        shift--;
+        divisor >>= 1;
+    }
+
+    return quotient;
+}
+
+static unsigned clz128(__uint128_t value) {
+    uint64_t high = (uint64_t)(value >> 64);
+
+    if (high != 0)
+        return (unsigned)__builtin_clzll(high);
+
+    return 64 + (unsigned)__builtin_clzll((uint64_t)value);
+}
+
+__uint128_t __udivmodti4(__uint128_t dividend, __uint128_t divisor, __uint128_t* remainder) {
+    if (divisor == 0) {
+        if (remainder)
+            *remainder = dividend;
+
+        return 0;
+    }
+
+    if (dividend < divisor) {
+        if (remainder)
+            *remainder = dividend;
+
+        return 0;
+    }
+
+    unsigned shift = clz128(divisor) - clz128(dividend);
+
+    divisor <<= shift;
+
+    __uint128_t quotient = 0;
+
+    for (;;) {
+        if (dividend >= divisor) {
+            dividend -= divisor;
+            quotient |= (__uint128_t)1 << shift;
+        }
+
+        if (shift == 0)
+            break;
+
+        shift--;
+        divisor >>= 1;
+    }
+
+    if (remainder)
+        *remainder = dividend;
+
+    return quotient;
+}
+
+__uint128_t __udivti3(__uint128_t dividend, __uint128_t divisor) {
+    return __udivmodti4(dividend, divisor, nullptr);
+}
+
+__uint128_t __umodti3(__uint128_t dividend, __uint128_t divisor) {
+    __uint128_t remainder;
+
+    __udivmodti4(dividend, divisor, &remainder);
+
+    return remainder;
+}

meson.build

@@ -74,8 +74,6 @@ kernel_c_args = ['-DIN_KERNEL']
 
 kernel_lds = meson.current_source_dir() / 'boot' / 'kernel.ld'
 kernel_link_args = [
-    '-lgcc',
-    '-static-libgcc',
     '-T' + kernel_lds,
     '-Wl,--export-dynamic',
 ]