boot2

Playing with the boostrap
git clone https://git.ryansepassi.com/git/boot2.git
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341-riscv64-u32-register-narrow.c (1251B)

      1 /* A 64-bit expression narrowed to unsigned int must discard bits 63:32
      2  * even when it stays in a register.  RISC-V comparisons operate on the
      3  * full XLEN register, so stale upper bits otherwise make an immediately
      4  * following unsigned relational comparison use the pre-cast u64 value.
      5  *
      6  * Keep the value behind a call: local lvalues are loaded with LW and do
      7  * not exercise the unspilled-register path. */
      8 typedef unsigned int u32;
      9 typedef unsigned long u64;
     10 
     11 static u64 ident(u64 x)
     12 {
     13     return x;
     14 }
     15 
     16 int main(void)
     17 {
     18     u32 one = 1;
     19 
     20     if (!((u32)ident(0x1234567800000000UL) < 1U))
     21         return 1;
     22     if ((u32)ident(0x1234567800000000UL) >= one)
     23         return 2;
     24     if (!((u32)ident(0x1234567800000000UL) <
     25           (u32)ident(0xabcdef0100000001UL)))
     26         return 3;
     27 
     28     if ((u32)ident(0x12345678ffffffffUL) != 0xffffffffU)
     29         return 4;
     30     if ((u64)(u32)ident(0x12345678ffffffffUL) != 0xffffffffUL)
     31         return 5;
     32     if ((u32)ident(0x1234567880000000UL) != 0x80000000U)
     33         return 6;
     34     if ((u64)(u32)ident(0x1234567880000000UL) != 0x80000000UL)
     35         return 7;
     36     if (!((int)ident(0x1234567800000000UL) < 1))
     37         return 8;
     38     if ((int)ident(0x12345678ffffffffUL) != -1)
     39         return 9;
     40 
     41     return 0;
     42 }