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Optimize special cases of immediate value extraction.

This commit is contained in:
Stephen Williams 2014-11-22 10:38:16 -08:00
parent f3392561ed
commit 679021a1b5
1 changed files with 21 additions and 0 deletions
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21
vvp/vthread.cc
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@ -806,12 +806,33 @@ bool of_AND(vthread_t thr, vvp_code_t)
return true;
}
/*
* This function must ALWAYS be called with the val set to the right
* size, and initialized with BIT4_0 bits. Certain optimizations rely
* on that.
*/
static void get_immediate_rval(vvp_code_t cp, vvp_vector4_t&val)
{
uint32_t vala = cp->bit_idx[0];
uint32_t valb = cp->bit_idx[1];
unsigned wid = cp->number;
if (valb == 0) {
// Special case: if the value is zero, we are done
// before we start.
if (vala == 0) return;
// Special case: The value has no X/Z bits, so we can
// use the setarray method to write the value all at once.
unsigned use_wid = 8*sizeof(unsigned long);
if (wid < use_wid)
use_wid = wid;
unsigned long tmp[1];
tmp[0] = vala;
val.setarray(0, use_wid, tmp);
return;
}
// The immediate value can be values bigger then 32 bits, but
// only if the high bits are zero. So at most we need to run
// through the loop below 32 times. Maybe less, if the target