[Tinycc-devel] Re: Please comment this patch, if you have the time.

[Jakob Eriksson]

Rob Landley wrote:
>
> Getting back to "that's a horrible name for this proposed function"...
>
> Let's see, according to http://sandpile.org/ia32 the opcode 0x85 is "TEST 
> Eb,Gb" and 0x0f is the prefix to indicate a two byte opcode follows.  At a 
> guess the function name indicates an x86 "test and jump".
>
> Except that the function _contents_ start by sticking 0x1a at the start of 
> it, 
> which is "SBB Gb, Eb" and I have no _IDEA_ what that means, but google 
> probably will...  http://en.wikipedia.org/wiki/X86_assembly_language
> says "subtraction with borrow".  Ok...
>
> Anybody else understand what this is doing?
>   

By the way, this is (almost) the patch Rob was referring to.

regards,
Jakob

diff -r c8a874736ed2 arm-gen.c
--- a/arm-gen.c Thu Sep 27 19:29:20 2007 -0500
+++ b/arm-gen.c Thu Sep 27 08:44:17 2007 +0200
@@ -1695,6 +1695,34 @@ void ggoto(void)
   vtop--;
 }
 
+int gen_jnz(int ind)
+{
+    o(0x1A000000 | encbranch(ind, 0, 1));
+
+    return ind;
+}
+
+const int double_align =
+#ifdef TCC_ARM_EABI
+    8
+#else
+    4
+#endif
+    ;
+
+int tcc_define_symbols_platform(TCCState *s)
+{
+    tcc_define_symbol(s, "__ARM_ARCH_4__", NULL);
+    tcc_define_symbol(s, "__arm_elf__", NULL);
+    tcc_define_symbol(s, "__arm_elf", NULL);
+    tcc_define_symbol(s, "arm_elf", NULL);
+    tcc_define_symbol(s, "__arm__", NULL);
+    tcc_define_symbol(s, "__arm", NULL);
+    tcc_define_symbol(s, "arm", NULL);
+    tcc_define_symbol(s, "__APCS_32__", NULL);
+}
+
+
 /* end of ARM code generator */
 /*************************************************************/
 
diff -r c8a874736ed2 c67-gen.c
--- a/c67-gen.c Thu Sep 27 19:29:20 2007 -0500
+++ b/c67-gen.c Thu Sep 27 08:44:35 2007 +0200
@@ -2544,5 +2544,13 @@ void ggoto(void)
     vtop--;
 }
 
-/* end of X86 code generator */
+int gen_jnz(int ind)
+{
+    error ("not implemented");
+    
+    return 0;
+}
+
+
+/* end of C67 code generator */
 /*************************************************************/
diff -r c8a874736ed2 i386/i386-asm.c
--- a/i386/i386-asm.c   Thu Sep 27 19:29:20 2007 -0500
+++ b/i386/i386-asm.c   Wed Sep 26 22:27:40 2007 +0200
@@ -1207,3 +1207,9 @@ static void asm_clobber(uint8_t *clobber
     }
     clobber_regs[reg] = 1;
 }
+
+int gen_jnz(int ind)
+{
+    return psym(0x850f, 0);
+}
+
diff -r c8a874736ed2 i386/i386-gen.c
--- a/i386/i386-gen.c   Thu Sep 27 19:29:20 2007 -0500
+++ b/i386/i386-gen.c   Fri Sep 28 18:28:51 2007 +0200
@@ -1022,6 +1022,21 @@ void gen_bounded_ptr_deref(void)
         put_extern_sym(sym, NULL, 0, 0);
     rel->r_info = ELF32_R_INFO(sym->c, ELF32_R_TYPE(rel->r_info));
 }
+
+void inline pop_fp_r (int r)
+{
+    if (TREG_ST0 == r) {
+        o(0xd9dd); /* fstp %st(1) */
+    }
+}
+
+const int double_align = 4;
+
+int tcc_define_symbols_platform(TCCState *s)
+{
+    tcc_define_symbol(s, "__i386__", NULL);
+}
+
 #endif
 
 /* end of X86 code generator */
diff -r c8a874736ed2 tcc.c
--- a/tcc.c     Thu Sep 27 19:29:20 2007 -0500
+++ b/tcc.c     Fri Sep 28 22:59:12 2007 +0200
@@ -3754,12 +3754,9 @@ void save_reg(int r)
                 sv.r = VT_LOCAL | VT_LVAL;
                 sv.c.ul = loc;
                 store(r, &sv);
-#ifdef TCC_TARGET_I386
-                /* x86 specific: need to pop fp register ST0 if saved */
-                if (r == TREG_ST0) {
-                    o(0xd9dd); /* fstp %st(1) */
-                }
-#endif
+
+                pop_fp_r (r);
+
                 /* special long long case */
                 if ((type->t & VT_BTYPE) == VT_LLONG) {
                     sv.c.ul += 4;
@@ -4195,12 +4192,7 @@ void vpop(void)
 {
     int v;
     v = vtop->r & VT_VALMASK;
-#ifdef TCC_TARGET_I386
-    /* for x86, we need to pop the FP stack */
-    if (v == TREG_ST0) {
-        o(0xd9dd); /* fstp %st(1) */
-    } else
-#endif
+    pop_fp_r (v);
     if (v == VT_JMP || v == VT_JMPI) {
         /* need to put correct jump if && or || without test */
         gsym(vtop->c.ul);
@@ -4447,16 +4439,7 @@ void gen_opl(int op)
             if (a == 0) {
                 b = gtst(0, 0);
             } else {
-#if defined(TCC_TARGET_I386)
-                b = psym(0x850f, 0);
-#elif defined(TCC_TARGET_ARM)
-                b = ind;
-                o(0x1A000000 | encbranch(ind, 0, 1));
-#elif defined(TCC_TARGET_C67)
-                error("not implemented");
-#else
-#error not supported
-#endif
+                b = gen_jnz (ind);
             }
         }
         /* compare low. Always unsigned */
@@ -4588,9 +4571,12 @@ void gen_opic(int op)
             vtop->c.i += fc;
         } else {
         general_case:
-            /* call low level op generator */
-            if (cur_text_section) gen_opi(op);
-            else vtop--;
+            if (!nocode_wanted) {
+                /* call low level op generator */
+                gen_opi(op);
+            } else {
+                vtop--;
+            }
         }
     }
 }
@@ -4651,8 +4637,11 @@ void gen_opif(int op)
         vtop--;
     } else {
     general_case:
-        if (cur_text_section) gen_opf(op);
-        else vtop--;
+        if (!nocode_wanted) {
+            gen_opf(op);
+        } else {
+            vtop--;
+        }
     }
 }
 
@@ -4954,7 +4943,7 @@ static void gen_cast(CType *type)
     dbt = type->t & (VT_BTYPE | VT_UNSIGNED);
     sbt = vtop->type.t & (VT_BTYPE | VT_UNSIGNED);
 
-    if (sbt != dbt && cur_text_section) {
+    if (sbt != dbt && !nocode_wanted) {
         sf = is_float(sbt);
         df = is_float(dbt);
         c = (vtop->r & (VT_VALMASK | VT_LVAL | VT_SYM)) == VT_CONST;
@@ -5133,17 +5122,7 @@ static int type_size(CType *type, int *a
         *a = LDOUBLE_ALIGN;
         return LDOUBLE_SIZE;
     } else if (bt == VT_DOUBLE || bt == VT_LLONG) {
-#ifdef TCC_TARGET_I386
-        *a = 4;
-#elif defined(TCC_TARGET_ARM)
-#ifdef TCC_ARM_EABI
-        *a = 8;
-#else
-        *a = 4;
-#endif
-#else
-        *a = 8;
-#endif
+        *a = double_align;
         return 8;
     } else if (bt == VT_INT || bt == VT_ENUM || bt == VT_FLOAT) {
         *a = 4;
@@ -5433,7 +5412,7 @@ void vstore(void)
         /* if structure, only generate pointer */
         /* structure assignment : generate memcpy */
         /* XXX: optimize if small size */
-        if (cur_text_section) {
+        if (!nocode_wanted) {
             size = type_size(&vtop->type, &align);
 
 #ifdef TCC_ARM_EABI
@@ -5505,7 +5484,7 @@ void vstore(void)
             vswap();
         }
 #endif
-        if (cur_text_section) {
+        if (!nocode_wanted) {
             rc = RC_INT;
             if (is_float(ft))
                 rc = RC_FLOAT;
@@ -6252,7 +6231,7 @@ static void indir(void)
             return;
         expect("pointer");
     }
-    if ((vtop->r & VT_LVAL) && cur_text_section)
+    if ((vtop->r & VT_LVAL) && !nocode_wanted)
         gv(RC_INT);
     vtop->type = *pointed_type(&vtop->type);
     /* Arrays and functions are never lvalues */
@@ -6523,16 +6502,15 @@ static void unary(void)
         break;
     case TOK_builtin_constant_p:
         {
-            Section *saved_text_section;
-            int res;
+            int saved_nocode_wanted, res;
             next();
             skip('(');
-            saved_text_section = cur_text_section;
-            cur_text_section = NULL;
+            saved_nocode_wanted = nocode_wanted;
+            nocode_wanted = 1;
             gexpr();
             res = (vtop->r & (VT_VALMASK | VT_LVAL | VT_SYM)) == VT_CONST;
             vpop();
-            cur_text_section = saved_text_section;
+            nocode_wanted = saved_nocode_wanted;
             skip(')');
             vpushi(res);
         }
@@ -6720,8 +6698,11 @@ static void unary(void)
             if (sa)
                 error("too few arguments to function");
             skip(')');
-            if (cur_text_section) gfunc_call(nb_args);
-            else vtop -= (nb_args + 1);
+            if (!nocode_wanted) {
+                gfunc_call(nb_args);
+            } else {
+                vtop -= (nb_args + 1);
+            }
             /* return value */
             vsetc(&ret.type, ret.r, &ret.c);
             vtop->r2 = ret.r2;
@@ -7055,26 +7036,28 @@ static void gexpr(void)
 /* parse an expression and return its type without any side effect. */
 static void expr_type(CType *type)
 {
-    Section *saved_text_section = cur_text_section;
-
-    cur_text_section = NULL;
+    int saved_nocode_wanted;
+
+    saved_nocode_wanted = nocode_wanted;
+    nocode_wanted = 1;
     gexpr();
     *type = vtop->type;
     vpop();
-    cur_text_section = saved_text_section;
+    nocode_wanted = saved_nocode_wanted;
 }
 
 /* parse a unary expression and return its type without any side
    effect. */
 static void unary_type(CType *type)
 {
-    Section *saved_text_section = cur_text_section;
-
-    cur_text_section = NULL;
+    int a;
+
+    a = nocode_wanted;
+    nocode_wanted = 1;
     unary();
     *type = vtop->type;
     vpop();
-    cur_text_section = saved_text_section;
+    nocode_wanted = a;
 }
 
 /* parse a constant expression and return value in vtop.  */
@@ -7605,7 +7588,7 @@ static void init_putv(CType *type, Secti
         expr_eq();
         break;
     }
-
+    
     dtype = *type;
     dtype.t &= ~VT_CONSTANT; /* need to do that to avoid false warning */
 
@@ -8410,6 +8393,8 @@ static void decl(int l)
                            extern */
                         external_sym(v, &type, r);
                     } else {
+                        int saved_nocode_wanted = nocode_wanted;
+
                         type.t |= (btype.t & VT_STATIC); // Retain "static".
                         if (type.t & VT_STATIC)
                             r |= VT_CONST;
@@ -8417,8 +8402,10 @@ static void decl(int l)
                             r |= l;
                         if (has_init)
                             next();
+                        nocode_wanted = !cur_text_section;
                         decl_initializer_alloc(&type, &ad, r, 
                                                has_init, v, l);
+                        nocode_wanted = saved_nocode_wanted;
                     }
                 }
                 if (tok != ',') {
@@ -8441,7 +8428,8 @@ static void preprocess_init(TCCState *s1
     s1->ifdef_stack_ptr = s1->ifdef_stack;
     file->ifdef_stack_ptr = s1->ifdef_stack_ptr;
 
-    vtop = vstack;
+    /* XXX: not ANSI compliant: bound checking says error */
+    vtop = vstack - 1;
     s1->pack_stack[0] = 0;
     s1->pack_stack_ptr = s1->pack_stack;
 }
@@ -8826,19 +8814,7 @@ TCCState *tcc_new(void)
     /* standard defines */
     tcc_define_symbol(s, "__STDC__", NULL);
     tcc_define_symbol(s, "__STDC_VERSION__", "199901L");
-#if defined(TCC_TARGET_I386)
-    tcc_define_symbol(s, "__i386__", NULL);
-#endif
-#if defined(TCC_TARGET_ARM)
-    tcc_define_symbol(s, "__ARM_ARCH_4__", NULL);
-    tcc_define_symbol(s, "__arm_elf__", NULL);
-    tcc_define_symbol(s, "__arm_elf", NULL);
-    tcc_define_symbol(s, "arm_elf", NULL);
-    tcc_define_symbol(s, "__arm__", NULL);
-    tcc_define_symbol(s, "__arm", NULL);
-    tcc_define_symbol(s, "arm", NULL);
-    tcc_define_symbol(s, "__APCS_32__", NULL);
-#endif
+    tcc_define_symbols_platform(s);
 #if defined(linux)
     tcc_define_symbol(s, "__linux__", NULL);
     tcc_define_symbol(s, "linux", NULL);