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a lot simpler VLA code

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Author: Philip <pipcet@gmail.com>
    Our VLA code can be made a lot simpler (simple enough for
    even me to understand it) by giving up on the optimization idea, which
    is very tempting. There's a patch to do that attached, feel free to
    test and commit it if you like. (It passes all the tests, at least
This commit is contained in:
seyko 2015-05-04 04:09:05 +03:00
parent fca58734fb
commit 999274ca90
4 changed files with 33 additions and 94 deletions
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4
i386-gen.c
View file

@ -1126,11 +1126,7 @@ ST_FUNC void gen_vla_alloc(CType *type, int align) {
/* We align to 16 bytes rather than align */ /* We align to 16 bytes rather than align */
/* and ~15, %esp */ /* and ~15, %esp */
o(0xf0e483); o(0xf0e483);
/* mov %esp, r */
o(0x89);
o(0xe0 | r);
vpop(); vpop();
vset(type, r, 0);
#endif #endif
} }

6
tcc.h
View file

@ -464,12 +464,6 @@ typedef struct DLLReference {
#define SYM_FIELD 0x20000000 /* struct/union field symbol space */ #define SYM_FIELD 0x20000000 /* struct/union field symbol space */
#define SYM_FIRST_ANOM 0x10000000 /* first anonymous sym */ #define SYM_FIRST_ANOM 0x10000000 /* first anonymous sym */
#define VLA_SP_LOC_SET 0x01 /* Location of SP on stack has been allocated */
#define VLA_SP_SAVED 0x02 /* SP has been saved to slot already */
#define VLA_NEED_NEW_FRAME 0x04 /* Needs new frame for next VLA */
#define VLA_IN_SCOPE 0x08 /* One or more VLAs are in scope */
#define VLA_SCOPE_FLAGS (VLA_SP_SAVED|VLA_NEED_NEW_FRAME|VLA_IN_SCOPE) /* Flags which are saved and restored upon entering and exiting a block */
/* stored in 'Sym.c' field */ /* stored in 'Sym.c' field */
#define FUNC_NEW 1 /* ansi function prototype */ #define FUNC_NEW 1 /* ansi function prototype */
#define FUNC_OLD 2 /* old function prototype */ #define FUNC_OLD 2 /* old function prototype */

113
tccgen.c
View file

@ -55,10 +55,9 @@ ST_DATA Sym *define_stack;
ST_DATA Sym *global_label_stack; ST_DATA Sym *global_label_stack;
ST_DATA Sym *local_label_stack; ST_DATA Sym *local_label_stack;
ST_DATA int vla_sp_loc_tmp; /* vla_sp_loc is set to this when the value won't be needed later */ ST_DATA int vlas_in_scope; /* number of VLAs that are currently in scope */
ST_DATA int vla_sp_root_loc; /* vla_sp_loc for SP before any VLAs were pushed */ ST_DATA int vla_sp_root_loc; /* vla_sp_loc for SP before any VLAs were pushed */
ST_DATA int *vla_sp_loc; /* Pointer to variable holding location to store stack pointer on the stack when modifying stack pointer */ ST_DATA int vla_sp_loc; /* Pointer to variable holding location to store stack pointer on the stack when modifying stack pointer */
ST_DATA int vla_flags; /* VLA_* flags */
ST_DATA SValue __vstack[1+VSTACK_SIZE], *vtop; ST_DATA SValue __vstack[1+VSTACK_SIZE], *vtop;
@ -87,7 +86,8 @@ static int decl0(int l, int is_for_loop_init);
static void expr_eq(void); static void expr_eq(void);
static void unary_type(CType *type); static void unary_type(CType *type);
static void vla_runtime_type_size(CType *type, int *a); static void vla_runtime_type_size(CType *type, int *a);
static void vla_sp_save(void); static void vla_sp_restore(void);
static void vla_sp_restore_root(void);
static int is_compatible_parameter_types(CType *type1, CType *type2); static int is_compatible_parameter_types(CType *type1, CType *type2);
static void expr_type(CType *type); static void expr_type(CType *type);
ST_FUNC void vpush64(int ty, unsigned long long v); ST_FUNC void vpush64(int ty, unsigned long long v);
@ -2223,14 +2223,15 @@ ST_FUNC void vla_runtime_type_size(CType *type, int *a)
} }
} }
static void vla_sp_save(void) { static void vla_sp_restore(void) {
if (!(vla_flags & VLA_SP_LOC_SET)) { if (vlas_in_scope) {
*vla_sp_loc = (loc -= PTR_SIZE); gen_vla_sp_restore(vla_sp_loc);
vla_flags |= VLA_SP_LOC_SET;
} }
if (!(vla_flags & VLA_SP_SAVED)) { }
gen_vla_sp_save(*vla_sp_loc);
vla_flags |= VLA_SP_SAVED; static void vla_sp_restore_root(void) {
if (vlas_in_scope) {
gen_vla_sp_restore(vla_sp_root_loc);
} }
} }
@ -4794,10 +4795,7 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
} else if (tok == TOK_WHILE) { } else if (tok == TOK_WHILE) {
next(); next();
d = ind; d = ind;
if (vla_flags & VLA_IN_SCOPE) { vla_sp_restore();
gen_vla_sp_restore(*vla_sp_loc);
vla_flags |= VLA_NEED_NEW_FRAME;
}
skip('('); skip('(');
gexpr(); gexpr();
skip(')'); skip(')');
@ -4809,7 +4807,7 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
gsym_addr(b, d); gsym_addr(b, d);
} else if (tok == '{') { } else if (tok == '{') {
Sym *llabel; Sym *llabel;
int block_vla_sp_loc, *saved_vla_sp_loc, saved_vla_flags, *orig_vla_sp_loc; int block_vla_sp_loc = vla_sp_loc, saved_vlas_in_scope = vlas_in_scope;
next(); next();
/* record local declaration stack position */ /* record local declaration stack position */
@ -4819,15 +4817,6 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
scope_stack_bottom = frame_bottom; scope_stack_bottom = frame_bottom;
llabel = local_label_stack; llabel = local_label_stack;
/* save VLA state */
block_vla_sp_loc = *(saved_vla_sp_loc = vla_sp_loc);
if (saved_vla_sp_loc != &vla_sp_root_loc)
vla_sp_loc = &block_vla_sp_loc;
orig_vla_sp_loc = vla_sp_loc;
saved_vla_flags = vla_flags;
vla_flags |= VLA_NEED_NEW_FRAME;
/* handle local labels declarations */ /* handle local labels declarations */
if (tok == TOK_LABEL) { if (tok == TOK_LABEL) {
next(); next();
@ -4877,13 +4866,11 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
sym_pop(&local_stack, s); sym_pop(&local_stack, s);
/* Pop VLA frames and restore stack pointer if required */ /* Pop VLA frames and restore stack pointer if required */
if (saved_vla_sp_loc != &vla_sp_root_loc) if (vlas_in_scope > saved_vlas_in_scope) {
*saved_vla_sp_loc = block_vla_sp_loc; vla_sp_loc = saved_vlas_in_scope ? block_vla_sp_loc : vla_sp_root_loc;
if (vla_sp_loc != orig_vla_sp_loc) { vla_sp_restore();
gen_vla_sp_restore(*saved_vla_sp_loc);
} }
vla_sp_loc = saved_vla_sp_loc; vlas_in_scope = saved_vlas_in_scope;
vla_flags = (vla_flags & ~VLA_SCOPE_FLAGS) | (saved_vla_flags & VLA_SCOPE_FLAGS);
next(); next();
} else if (tok == TOK_RETURN) { } else if (tok == TOK_RETURN) {
@ -4964,13 +4951,7 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
/* compute jump */ /* compute jump */
if (!csym) if (!csym)
tcc_error("cannot continue"); tcc_error("cannot continue");
if (vla_flags & VLA_IN_SCOPE) { vla_sp_restore_root();
/* If VLAs are in use, save the current stack pointer and
reset the stack pointer to what it was at function entry
(label will restore stack pointer in inner scopes) */
vla_sp_save();
gen_vla_sp_restore(vla_sp_root_loc);
}
*csym = gjmp(*csym); *csym = gjmp(*csym);
next(); next();
skip(';'); skip(';');
@ -4993,10 +4974,7 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
skip(';'); skip(';');
d = ind; d = ind;
c = ind; c = ind;
if (vla_flags & VLA_IN_SCOPE) { vla_sp_restore();
gen_vla_sp_restore(*vla_sp_loc);
vla_flags |= VLA_NEED_NEW_FRAME;
}
a = 0; a = 0;
b = 0; b = 0;
if (tok != ';') { if (tok != ';') {
@ -5007,10 +4985,7 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
if (tok != ')') { if (tok != ')') {
e = gjmp(0); e = gjmp(0);
c = ind; c = ind;
if (vla_flags & VLA_IN_SCOPE) { vla_sp_restore();
gen_vla_sp_restore(*vla_sp_loc);
vla_flags |= VLA_NEED_NEW_FRAME;
}
gexpr(); gexpr();
vpop(); vpop();
gjmp_addr(d); gjmp_addr(d);
@ -5029,10 +5004,7 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
a = 0; a = 0;
b = 0; b = 0;
d = ind; d = ind;
if (vla_flags & VLA_IN_SCOPE) { vla_sp_restore();
gen_vla_sp_restore(*vla_sp_loc);
vla_flags |= VLA_NEED_NEW_FRAME;
}
block(&a, &b, case_sym, def_sym, case_reg, 0); block(&a, &b, case_sym, def_sym, case_reg, 0);
skip(TOK_WHILE); skip(TOK_WHILE);
skip('('); skip('(');
@ -5130,14 +5102,7 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
if (s->r == LABEL_DECLARED) if (s->r == LABEL_DECLARED)
s->r = LABEL_FORWARD; s->r = LABEL_FORWARD;
} }
/* label already defined */ vla_sp_restore_root();
if (vla_flags & VLA_IN_SCOPE) {
/* If VLAs are in use, save the current stack pointer and
reset the stack pointer to what it was at function entry
(label will restore stack pointer in inner scopes) */
vla_sp_save();
gen_vla_sp_restore(vla_sp_root_loc);
}
if (s->r & LABEL_FORWARD) if (s->r & LABEL_FORWARD)
s->jnext = gjmp(s->jnext); s->jnext = gjmp(s->jnext);
else else
@ -5153,12 +5118,6 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
b = is_label(); b = is_label();
if (b) { if (b) {
/* label case */ /* label case */
if (vla_flags & VLA_IN_SCOPE) {
/* save/restore stack pointer across label
this is a no-op when combined with the load immediately
after the label unless we arrive via goto */
vla_sp_save();
}
s = label_find(b); s = label_find(b);
if (s) { if (s) {
if (s->r == LABEL_DEFINED) if (s->r == LABEL_DEFINED)
@ -5169,10 +5128,7 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
s = label_push(&global_label_stack, b, LABEL_DEFINED); s = label_push(&global_label_stack, b, LABEL_DEFINED);
} }
s->jnext = ind; s->jnext = ind;
if (vla_flags & VLA_IN_SCOPE) { vla_sp_restore();
gen_vla_sp_restore(*vla_sp_loc);
vla_flags |= VLA_NEED_NEW_FRAME;
}
/* we accept this, but it is a mistake */ /* we accept this, but it is a mistake */
block_after_label: block_after_label:
if (tok == '}') { if (tok == '}') {
@ -5476,20 +5432,17 @@ static void decl_initializer(CType *type, Section *sec, unsigned long c,
int a; int a;
/* save current stack pointer */ /* save current stack pointer */
if (vla_flags & VLA_NEED_NEW_FRAME) { if (vlas_in_scope == 0) {
vla_sp_save(); if (vla_sp_root_loc == -1)
vla_flags = VLA_IN_SCOPE; vla_sp_root_loc = (loc -= PTR_SIZE);
vla_sp_loc = &vla_sp_loc_tmp; gen_vla_sp_save(vla_sp_root_loc);
} }
vla_runtime_type_size(type, &a); vla_runtime_type_size(type, &a);
gen_vla_alloc(type, a); gen_vla_alloc(type, a);
vla_flags = VLA_IN_SCOPE; gen_vla_sp_save(c);
vla_sp_save(); vla_sp_loc = c;
vset(type, VT_LOCAL|VT_LVAL, c); vlas_in_scope++;
vswap();
vstore();
vpop();
} else if (type->t & VT_ARRAY) { } else if (type->t & VT_ARRAY) {
s = type->ref; s = type->ref;
n = s->c; n = s->c;
@ -6072,8 +6025,8 @@ static void gen_function(Sym *sym)
funcname = get_tok_str(sym->v, NULL); funcname = get_tok_str(sym->v, NULL);
func_ind = ind; func_ind = ind;
/* Initialize VLA state */ /* Initialize VLA state */
vla_sp_loc = &vla_sp_root_loc; vla_sp_loc = -1;
vla_flags = VLA_NEED_NEW_FRAME; vla_sp_root_loc = -1;
/* put debug symbol */ /* put debug symbol */
if (tcc_state->do_debug) if (tcc_state->do_debug)
put_func_debug(sym); put_func_debug(sym);

4
x86_64-gen.c
View file

@ -2240,11 +2240,7 @@ ST_FUNC void gen_vla_alloc(CType *type, int align) {
/* We align to 16 bytes rather than align */ /* We align to 16 bytes rather than align */
/* and ~15, %rsp */ /* and ~15, %rsp */
o(0xf0e48348); o(0xf0e48348);
/* mov %rsp, r */
o(0x8948);
o(0xe0 | REG_VALUE(r));
vpop(); vpop();
vset(type, r, 0);
#endif #endif
} }