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Pad expression in place 

When padding expressions, pre-allocate the target space and calculate
the sub-expression directly into the target. Then pad from there. This
saves a move into the result space.
This commit is contained in:
Stephen Williams 2008-11-21 21:12:40 -08:00
parent f502d4c8ad
commit bc8b97dbcd
1 changed files with 21 additions and 12 deletions
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33
tgt-vvp/eval_expr.c
View File

@ -1599,7 +1599,7 @@ static struct vector_info draw_concat_expr(ivl_expr_t exp, unsigned wid,
if (avec.base != 0) {
assert(awid == avec.wid);
fprintf(vvp_out, " %%mov %u, %u, %u;\n",
fprintf(vvp_out, " %%mov %u, %u, %u; Reuse calculated expression\n",
res.base+off,
avec.base, trans);
clr_vector(avec);
@ -1790,17 +1790,27 @@ static struct vector_info draw_pad_expr(ivl_expr_t exp, unsigned wid)
struct vector_info subv;
struct vector_info res;
subv = draw_eval_expr(ivl_expr_oper1(exp), 0);
if (wid <= subv.wid) {
if (subv.base >= 8)
save_expression_lookaside(subv.base, exp, subv.wid);
ivl_expr_t subexpr = ivl_expr_oper1(exp);
/* If the sub-expression is at least as wide as the target
width, then instead of pad, we truncate. Evaluate the
expression and return that expression with the width
reduced to what we want. */
if (wid <= ivl_expr_width(subexpr)) {
subv = draw_eval_expr(subexpr, 0);
assert(subv.wid >= wid);
res.base = subv.base;
res.wid = wid;
if (subv.base >= 8)
save_expression_lookaside(subv.base, exp, subv.wid);
return res;
}
/* So now we know that the subexpression is smaller then the
desired result (the usual case) so we build the
result. Evaluate the subexpression into the target buffer,
then pad it as appropriate. */
res.base = allocate_vector(wid);
res.wid = wid;
if (res.base == 0) {
fprintf(stderr, "%s:%u: vvp.tgt error: "
"Unable to allocate %u thread bits "
@ -1809,10 +1819,11 @@ static struct vector_info draw_pad_expr(ivl_expr_t exp, unsigned wid)
vvp_errors += 1;
}
fprintf(vvp_out, " %%mov %u, %u, %u;\n",
res.base, subv.base, subv.wid);
res.wid = wid;
assert(wid > subv.wid);
subv.base = res.base;
subv.wid = ivl_expr_width(subexpr);
draw_eval_expr_dest(subexpr, subv, 0);
if (ivl_expr_signed(exp)) {
unsigned idx;
@ -1823,9 +1834,7 @@ static struct vector_info draw_pad_expr(ivl_expr_t exp, unsigned wid)
fprintf(vvp_out, " %%mov %u, 0, %u;\n",
res.base+subv.wid, res.wid - subv.wid);
}
if (subv.base >= 8)
clr_vector(subv);
save_expression_lookaside(res.base, exp, wid);
return res;
}