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Reduce some vector copies in %load/vec4 and %concat/vec4 instructions. 

By clever stack manipulations, we can eliminate some vector copies,
which can improve performance.
This commit is contained in:
Stephen Williams 2014-12-03 13:12:06 -08:00
parent 85c7b07a9b
commit 2b1393e7b9
1 changed files with 27 additions and 33 deletions
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60
vvp/vthread.cc
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@ -1983,14 +1983,22 @@ bool of_CONCATI_STR(vthread_t thr, vvp_code_t cp)
*/
bool of_CONCAT_VEC4(vthread_t thr, vvp_code_t)
{
vvp_vector4_t lsb = thr->pop_vec4();
vvp_vector4_t&msb = thr->peek_vec4();
const vvp_vector4_t&lsb = thr->peek_vec4(0);
const vvp_vector4_t&msb = thr->peek_vec4(1);
vvp_vector4_t res (msb.size()+lsb.size(), BIT4_X);
// The result is the size of the top two vectors in the stack.
vvp_vector4_t res (msb.size() + lsb.size(), BIT4_X);
// Build up the result.
res.set_vec(0, lsb);
res.set_vec(lsb.size(), msb);
msb = res;
// Rearrange the stack to pop the inputs and push the
// result. Do that by actually popping only 1 stack position
// and replacing the new top with the new value.
thr->pop_vec4(1);
thr->peek_vec4() = res;
return true;
}
@ -3546,27 +3554,22 @@ bool of_LOAD_STRA(vthread_t thr, vvp_code_t cp)
return true;
}
/* %load/v <bit>, <label>, <wid>
*
* Implement the %load/v instruction. Load the vector value of the
* requested width from the <label> functor starting in the thread bit
* <bit>.
*
* The <bit> value is the destination in the thread vector store, and
* is in cp->bit_idx[0].
*
* The <wid> value is the expected with of the vector, and is in
* cp->bit_idx[1].
*
* The functor to read from is the vvp_net_t object pointed to by the
* cp->net pointer.
/*
* %load/vec4 <net>
*/
static void load_base(vvp_code_t cp, vvp_vector4_t&dst)
bool of_LOAD_VEC4(vthread_t thr, vvp_code_t cp)
{
// Push a placeholder onto the stack in order to reserve the
// stack space. Use a reference for the stack top as a target
// for the load.
thr->push_vec4(vvp_vector4_t());
vvp_vector4_t&sig_value = thr->peek_vec4();
vvp_net_t*net = cp->net;
/* For the %load to work, the functor must actually be a
signal functor. Only signals save their vector value. */
// For the %load to work, the functor must actually be a
// signal functor. Only signals save their vector value.
vvp_signal_value*sig = dynamic_cast<vvp_signal_value*> (net->fil);
if (sig == 0) {
cerr << "%load/v error: Net arg not a signal? "
@ -3574,18 +3577,9 @@ static void load_base(vvp_code_t cp, vvp_vector4_t&dst)
assert(sig);
}
sig->vec4_value(dst);
}
/*
* %load/vec4 <net>
*/
bool of_LOAD_VEC4(vthread_t thr, vvp_code_t cp)
{
vvp_vector4_t sig_value;
load_base(cp, sig_value);
thr->push_vec4(sig_value);
// Extract the value from the signal and directly into the
// target stack position.
sig->vec4_value(sig_value);
return true;
}