Support local register variables

Similar to GCC a local asm register variable enforces the use of a
specified register in asm operands (and doesn't otherwise
matter).  Works only if the variable is directly mentioned as
operand.  For that we now generally store a backpointer from
an SValue to a Sym when the SValue was the result of unary()
parsing a symbol identifier.

1 files changed, 5 insertions, 3 deletions

diff --git a/tcc.h b/tcc.h
index 2434b94..fb104fa 100644
--- a/tcc.h
+++ b/tcc.h
@@ -372,7 +372,8 @@ typedef struct SValue {
     unsigned short r2;     /* second register, used for 'long long'
                               type. If not used, set to VT_CONST */
     CValue c;              /* constant, if VT_CONST */
-    struct Sym *sym;       /* symbol, if (VT_SYM | VT_CONST) */
+    struct Sym *sym;       /* symbol, if (VT_SYM | VT_CONST), or if
+    			      result of unary() for an identifier. */
 } SValue;
 
 struct Attribute {
@@ -407,7 +408,7 @@ typedef struct Sym {
         int scope;  /* scope level for locals */
     };
     union {
-        long r;    /* associated register */
+        long r;    /* associated register or VT_CONST/VT_LOCAL and LVAL type */
         struct Attribute a;
     };
     union {
@@ -416,7 +417,7 @@ typedef struct Sym {
     };
     CType type;    /* associated type */
     union {
-        struct Sym *next; /* next related symbol */
+        struct Sym *next; /* next related symbol (for fields and anoms) */
         long jnext; /* next jump label */
     };
     struct Sym *prev; /* prev symbol in stack */
@@ -1542,6 +1543,7 @@ ST_FUNC void gen_expr32(ExprValue *pe);
 ST_FUNC void gen_expr64(ExprValue *pe);
 #endif
 ST_FUNC void asm_opcode(TCCState *s1, int opcode);
+ST_FUNC int asm_parse_regvar(int t);
 ST_FUNC void asm_compute_constraints(ASMOperand *operands, int nb_operands, int nb_outputs, const uint8_t *clobber_regs, int *pout_reg);
 ST_FUNC void subst_asm_operand(CString *add_str, SValue *sv, int modifier);
 ST_FUNC void asm_gen_code(ASMOperand *operands, int nb_operands, int nb_outputs, int is_output, uint8_t *clobber_regs, int out_reg);