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Optimize random initialization 

Fetching a thread-local is relatively expensive. Random initializing
wides used to do it once or twice per word, and on short runs for
large designs can be noticeably expensive, so fetch once per variable
instead. Also remove unused VL_RAND_RESET_{Q,W} functions.
This commit is contained in:
Geza Lore 2026-07-02 14:50:55 +01:00
parent 506f703da5
commit 1106e89c84
2 changed files with 20 additions and 31 deletions
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47
include/verilated.cpp
View File

@ -563,9 +563,10 @@ IData VL_URANDOM_SEEDED_II(IData seed) VL_MT_SAFE {
}
IData VL_SCOPED_RAND_RESET_I(int obits, uint64_t scopeHash, uint64_t salt) VL_MT_UNSAFE {
if (Verilated::threadContextp()->randReset() == 0) return 0;
const int randReset = Verilated::threadContextp()->randReset();
if (randReset == 0) return 0;
IData data = ~0;
if (Verilated::threadContextp()->randReset() != 1) { // if 2, randomize
if (randReset != 1) { // if 2, randomize
VlRNG rng{Verilated::threadContextp()->randSeed() ^ scopeHash ^ salt};
data = rng.rand64();
}
@ -574,9 +575,10 @@ IData VL_SCOPED_RAND_RESET_I(int obits, uint64_t scopeHash, uint64_t salt) VL_MT
}
QData VL_SCOPED_RAND_RESET_Q(int obits, uint64_t scopeHash, uint64_t salt) VL_MT_UNSAFE {
if (Verilated::threadContextp()->randReset() == 0) return 0;
const int randReset = Verilated::threadContextp()->randReset();
if (randReset == 0) return 0;
QData data = ~0ULL;
if (Verilated::threadContextp()->randReset() != 1) { // if 2, randomize
if (randReset != 1) { // if 2, randomize
VlRNG rng{Verilated::threadContextp()->randSeed() ^ scopeHash ^ salt};
data = rng.rand64();
}
@ -586,10 +588,17 @@ QData VL_SCOPED_RAND_RESET_Q(int obits, uint64_t scopeHash, uint64_t salt) VL_MT
WDataOutP VL_SCOPED_RAND_RESET_W(int obits, WDataOutP outwp, uint64_t scopeHash,
uint64_t salt) VL_MT_UNSAFE {
if (Verilated::threadContextp()->randReset() != 2) { return VL_RAND_RESET_W(obits, outwp); }
VlRNG rng{Verilated::threadContextp()->randSeed() ^ scopeHash ^ salt};
for (int i = 0; i < VL_WORDS_I(obits) - 1; ++i) outwp[i] = rng.rand64();
outwp[VL_WORDS_I(obits) - 1] = rng.rand64() & VL_MASK_E(obits);
const int words = VL_WORDS_I(obits);
const int randReset = Verilated::threadContextp()->randReset();
if (randReset == 0) {
VL_MEMSET_ZERO_W(outwp, words);
} else if (randReset == 1) {
VL_MEMSET_ONES_W(outwp, words);
} else {
VlRNG rng{Verilated::threadContextp()->randSeed() ^ scopeHash ^ salt};
for (int i = 0; i < words; ++i) outwp[i] = rng.rand64();
}
outwp[words - 1] &= VL_MASK_E(obits);
return outwp;
}
@ -614,30 +623,14 @@ WDataOutP VL_SCOPED_RAND_RESET_ASSIGN_W(int obits, WDataOutP outwp, uint64_t sco
}
IData VL_RAND_RESET_I(int obits) VL_MT_SAFE {
if (Verilated::threadContextp()->randReset() == 0) return 0;
const int randReset = Verilated::threadContextp()->randReset();
if (randReset == 0) return 0;
IData data = ~0;
if (Verilated::threadContextp()->randReset() != 1) { // if 2, randomize
data = VL_RANDOM_I();
}
if (randReset != 1) data = VL_RANDOM_I(); // if 2, randomize
data &= VL_MASK_I(obits);
return data;
}
QData VL_RAND_RESET_Q(int obits) VL_MT_SAFE {
if (Verilated::threadContextp()->randReset() == 0) return 0;
QData data = ~0ULL;
if (Verilated::threadContextp()->randReset() != 1) { // if 2, randomize
data = VL_RANDOM_Q();
}
data &= VL_MASK_Q(obits);
return data;
}
WDataOutP VL_RAND_RESET_W(int obits, WDataOutP outwp) VL_MT_SAFE {
for (int i = 0; i < VL_WORDS_I(obits) - 1; ++i) outwp[i] = VL_RAND_RESET_I(32);
outwp[VL_WORDS_I(obits) - 1] = VL_RAND_RESET_I(32) & VL_MASK_E(obits);
return outwp;
}
WDataOutP VL_ZERO_RESET_W(int obits, WDataOutP outwp) VL_MT_SAFE {
// Not inlined to speed up compilation of slowpath code
return VL_ZERO_W(obits, outwp);

4
include/verilated_funcs.h
View File

@ -124,10 +124,6 @@ extern WDataOutP VL_SCOPED_RAND_RESET_ASSIGN_W(int obits, WDataOutP outwp, uint6
/// Random reset a signal of given width (init time only)
extern IData VL_RAND_RESET_I(int obits) VL_MT_SAFE;
/// Random reset a signal of given width (init time only)
extern QData VL_RAND_RESET_Q(int obits) VL_MT_SAFE;
/// Random reset a signal of given width (init time only)
extern WDataOutP VL_RAND_RESET_W(int obits, WDataOutP outwp) VL_MT_SAFE;
/// Zero reset a signal (slow - else use VL_ZERO_W)
extern WDataOutP VL_ZERO_RESET_W(int obits, WDataOutP outwp) VL_MT_SAFE;