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jump optimizations

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This unifies VT_CMP with VT_JMP(i) by using mostly VT_CMP
with both a positive and a negative jump target list.

Such we can delay putting the non-inverted or inverted jump
until we can see which one is nore suitable (in most cases).

example:
    if (a && b || c && d)
        e = 0;

before this patch:
   a:	8b 45 fc             	mov    0xfffffffc(%ebp),%eax
   d:	83 f8 00             	cmp    $0x0,%eax
  10:	0f 84 11 00 00 00    	je     27 <main+0x27>
  16:	8b 45 f8             	mov    0xfffffff8(%ebp),%eax
  19:	83 f8 00             	cmp    $0x0,%eax
  1c:	0f 84 05 00 00 00    	je     27 <main+0x27>
  22:	e9 22 00 00 00       	jmp    49 <main+0x49>
  27:	8b 45 f4             	mov    0xfffffff4(%ebp),%eax
  2a:	83 f8 00             	cmp    $0x0,%eax
  2d:	0f 84 11 00 00 00    	je     44 <main+0x44>
  33:	8b 45 f0             	mov    0xfffffff0(%ebp),%eax
  36:	83 f8 00             	cmp    $0x0,%eax
  39:	0f 84 05 00 00 00    	je     44 <main+0x44>
  3f:	e9 05 00 00 00       	jmp    49 <main+0x49>
  44:	e9 08 00 00 00       	jmp    51 <main+0x51>
  49:	b8 00 00 00 00       	mov    $0x0,%eax
  4e:	89 45 ec             	mov    %eax,0xffffffec(%ebp)
  51:   ...

with this patch:
   a:	8b 45 fc             	mov    0xfffffffc(%ebp),%eax
   d:	83 f8 00             	cmp    $0x0,%eax
  10:	0f 84 0c 00 00 00    	je     22 <main+0x22>
  16:	8b 45 f8             	mov    0xfffffff8(%ebp),%eax
  19:	83 f8 00             	cmp    $0x0,%eax
  1c:	0f 85 18 00 00 00    	jne    3a <main+0x3a>
  22:	8b 45 f4             	mov    0xfffffff4(%ebp),%eax
  25:	83 f8 00             	cmp    $0x0,%eax
  28:	0f 84 14 00 00 00    	je     42 <main+0x42>
  2e:	8b 45 f0             	mov    0xfffffff0(%ebp),%eax
  31:	83 f8 00             	cmp    $0x0,%eax
  34:	0f 84 08 00 00 00    	je     42 <main+0x42>
  3a:	b8 00 00 00 00       	mov    $0x0,%eax
  3f:	89 45 ec             	mov    %eax,0xffffffec(%ebp)
  42:   ...
This commit is contained in:
grischka
2019-06-22 11:45:35 +02:00
parent 1b57560502
commit 8227db3a23
9 changed files with 346 additions and 283 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
c67-gen.c
View File

@@ -2072,15 +2072,13 @@ void gjmp_addr(int a)
}
/* generate a test. set 'inv' to invert test. Stack entry is popped */
int gtst(int inv, int t)
ST_FUNC int gjmp_cond(int op, int t)
{
int ind1, n;
int v, *p;
int ind1;
int inv = op & 1;
if (nocode_wanted)
return t;
v = vtop->r & VT_VALMASK;
if (nocode_wanted) {
;
} else if (v == VT_CMP) {
/* fast case : can jump directly since flags are set */
// C67 uses B2 sort of as flags register
ind1 = ind;
@@ -2098,16 +2096,18 @@ int gtst(int inv, int t)
C67_NOP(5);
t = ind1; //return where we need to patch
} else if (v == VT_JMP || v == VT_JMPI) {
/* && or || optimization */
if ((v & 1) == inv) {
return t;
}
ST_FUNC int gjmp_append(int n0, int t)
{
if (n0) {
int n = n0, *p;
/* insert vtop->c jump list in t */
// I guess the idea is to traverse to the
// null at the end of the list and store t
// there
n = vtop->c.i;
while (n != 0) {
p = (int *) (cur_text_section->data + n);
@@ -2117,14 +2117,8 @@ int gtst(int inv, int t)
}
*p |= (t & 0xffff) << 7;
*(p + 1) |= ((t >> 16) & 0xffff) << 7;
t = vtop->c.i;
} else {
t = gjmp(t);
gsym(vtop->c.i);
}
t = n0;
}
vtop--;
return t;
}
@@ -2200,10 +2194,8 @@ void gen_opi(int op)
ALWAYS_ASSERT(FALSE);
vtop--;
if (op >= TOK_ULT && op <= TOK_GT) {
vtop->r = VT_CMP;
vtop->c.i = op;
}
if (op >= TOK_ULT && op <= TOK_GT)
vset_VT_CMP(0x80);
break;
case '-':
case TOK_SUBC1: /* sub with carry generation */
@@ -2359,7 +2351,7 @@ void gen_opf(int op)
} else {
ALWAYS_ASSERT(FALSE);
}
vtop->r = VT_CMP; // tell TCC that result is in "flags" actually B2
vset_VT_CMP(0x80);
} else {
if (op == '+') {
if ((ft & VT_BTYPE) == VT_DOUBLE) {