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Minimal implementation of IVL_LPM_MUX 

This handles the (common) case of the select being only
1 bit wide. Implemented as a concurrent assignment with
a `when' clause.
This commit is contained in:
Nick Gasson 2008-08-03 12:46:50 +01:00
parent 45dfa28dba
commit 0e2628a3fb
1 changed files with 32 additions and 1 deletions
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33
tgt-vhdl/lpm.cc
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@ -266,11 +266,42 @@ static vhdl_expr *lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
}
}
static int draw_mux_lpm(vhdl_arch *arch, ivl_lpm_t lpm)
{
int nselects = ivl_lpm_selects(lpm);
if (nselects > 1) {
error("Only 1 LPM select bit supported at the moment");
return 1;
}
vhdl_scope *scope = arch->get_scope();
vhdl_expr *s0 = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 0));
vhdl_expr *s1 = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 1));
vhdl_expr *sel = nexus_to_var_ref(scope, ivl_lpm_select(lpm));
vhdl_expr *b1 = new vhdl_const_bit('1');
vhdl_expr *t1 =
new vhdl_binop_expr(sel, VHDL_BINOP_EQ, b1, vhdl_type::boolean());
vhdl_var_ref *out = nexus_to_var_ref(scope, ivl_lpm_q(lpm, 0));
vhdl_cassign_stmt *s = new vhdl_cassign_stmt(out, s0);
s->add_condition(s1, t1);
arch->add_stmt(s);
return 0;
}
int draw_lpm(vhdl_arch *arch, ivl_lpm_t lpm)
{
if (ivl_lpm_type(lpm) == IVL_LPM_MUX)
return draw_mux_lpm(arch, lpm);
vhdl_expr *f = lpm_to_expr(arch->get_scope(), lpm);
if (NULL == f)
return 0;
return 1;
vhdl_var_ref *out = nexus_to_var_ref(arch->get_scope(), ivl_lpm_q(lpm, 0));
if (ivl_lpm_type(lpm) == IVL_LPM_PART_PV) {