riscv: GOT loads, signed remainder, ELF flags

* support loading sym addresses from GOT: important for weak syms,
  fixes 104_inline.  This is still incomplete, it only works
  for taking the sym address, not for directly loading/storing into
  such symbols (i.e. not for VT_LVAL)
* another op: '%'
* ELF flags: add EF_RISCV_FLOAT_ABI_DOUBLE, which is our ABI.

riscv64-gen.c

@@ -189,12 +189,22 @@ ST_FUNC void load(int r, SValue *sv)
             tcc_error("unimp: load(non-local lval)");
         }
     } else if (v == VT_CONST) {
-        int rb = 0, do32bit = 8;
+        int rb = 0, do32bit = 8, doload = 0;
         assert(!is_float(sv->type.t) && is_ireg(r));
         if (fr & VT_SYM) {
             static Sym label;
+            if (sv->sym->type.t & VT_STATIC) { // XXX do this per linker relax
                 greloca(cur_text_section, sv->sym, ind,
                         R_RISCV_PCREL_HI20, sv->c.i);
+                fc = 0;
+                sv->c.i = 0;
+            } else {
+                if (((unsigned)fc + (1 << 11)) >> 12)
+                  tcc_error("unimp: large addend for global address");
+                greloca(cur_text_section, sv->sym, ind,
+                        R_RISCV_GOT_HI20, 0);
+                doload = 1;
+            }
             if (!label.v) {
                 label.v = tok_alloc(".L0 ", 4)->tok;
                 label.type.t = VT_VOID | VT_STATIC;
@@ -205,8 +215,6 @@ ST_FUNC void load(int r, SValue *sv)
             greloca(cur_text_section, &label, ind,
                     R_RISCV_PCREL_LO12_I, 0);
             rb = rr;
-            fc = 0;
-            sv->c.i = 0;
             do32bit = 0;
         }
         if (is_float(sv->type.t))
@@ -244,6 +252,11 @@ ST_FUNC void load(int r, SValue *sv)
         }
         if (((unsigned)fc + (1 << 11)) >> 12)
             o(0x37 | (rr << 7) | ((0x800 + fc) & 0xfffff000)), rb = rr; //lui RR, upper(fc)
+        if (doload) {
+          EI(0x03, 3, rr, rr, 0); // ld RR, 0(RR)
+          if (fc)
+            EI(0x13 | do32bit, 0, rr, rr, fc << 20 >> 20); // addi[w] R, x0|R, FC
+        } else
           EI(0x13 | do32bit, 0, rr, rb, fc << 20 >> 20); // addi[w] R, x0|R, FC
     } else if (v == VT_LOCAL) {
         assert(is_ireg(r));
@@ -636,7 +649,6 @@ static void gen_opil(int op, int ll)
     d = ireg(d);
     ll = ll ? 0 : 8;
     switch (op) {
-    case '%':
     case TOK_PDIV:
     default:
         tcc_error("implement me: %s(%s)", __FUNCTION__, get_tok_str(op, NULL));
@@ -671,6 +683,9 @@ static void gen_opil(int op, int ll)
     case '|':
         o(0x33 | (d << 7) | (a << 15) | (b << 20) | (6 << 12)); // or d, a, b
         break;
+    case '%':
+        o(0x33 | (d << 7) | (a << 15) | (b << 20) | (0x01 << 25) | (6 << 12)); //rem d, a, b
+        break;
     case TOK_UMOD:
         o(0x33 | (d << 7) | (a << 15) | (b << 20) | (0x01 << 25) | (7 << 12)); //remu d, a, b
         break;

riscv64-link.c

@@ -19,6 +19,7 @@
 
 #else /* !TARGET_DEFS_ONLY */
 
+//#define DEBUG_RELOC
 #include "tcc.h"
 
 /* Returns 1 for a code relocation, 0 for a data relocation. For unknown
@@ -177,9 +178,7 @@ void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr,
     uint64_t off64;
     uint32_t off32;
     int sym_index = ELFW(R_SYM)(rel->r_info);
-#ifdef DEBUG_RELOC
     ElfW(Sym) *sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
-#endif
 
     switch(type) {
     case R_RISCV_ALIGN:
@@ -223,8 +222,9 @@ void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr,
 #endif
         off64 = (int64_t)(val - addr + 0x800) >> 12;
         if ((off64 + ((uint64_t)1 << 20)) >> 21)
-          tcc_error("R_RISCV_PCREL_HI20 relocation failed: off=%lx cond=%lx",
+          tcc_error("R_RISCV_PCREL_HI20 relocation failed: off=%lx cond=%lx sym=%s",
-                    off64, ((int64_t)(off64 + ((uint64_t)1 << 20)) >> 21));
+                    off64, ((int64_t)(off64 + ((uint64_t)1 << 20)) >> 21),
+                    symtab_section->link->data + sym->st_name);
         write32le(ptr, (read32le(ptr) & 0xfff)
                        | ((off64 & 0xfffff) << 12));
         last_hi.addr = addr;

tccelf.c

@@ -1910,6 +1910,8 @@ static void tcc_output_elf(TCCState *s1, FILE *f, int phnum, ElfW(Phdr) *phdr,
 #else
     ehdr.e_ident[EI_OSABI] = ELFOSABI_ARM;
 #endif
+#elif defined TCC_TARGET_RISCV64
+    ehdr.e_flags = EF_RISCV_FLOAT_ABI_DOUBLE;
 #endif
     switch(file_type) {
     default: