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Various minor optimizations of VCD trace routines

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- Change templated trace routines to branch table.

Removed templating from trace chgBus and fullBus and replaced them with
a branch table like the other there is a very small (< 1%) penalty for
this on SwerRV EH1 CoreMark, but this is less than the variability of
disk IO so it's worth it to keep the code simpler and smaller.

- Prefetch VCD suffix buffer at the top of emit*

- Increase ILP in VCD emit* routines

- Use a 64-bit unaligned store to emit the VCD suffix (on x86 only)

The performance difference with these is very small, but the changes
hopefully make this code more performance-portable across various
micro-architectures.
This commit is contained in:
Geza Lore
2020-04-27 18:44:53 +01:00
parent 70549e1a64
commit b79ef672e1
7 changed files with 205 additions and 192 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/verilated_trace_imp.cpp
+7 -79
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@@ -161,50 +161,15 @@ template <> void VerilatedTrace<VL_DERIVED_T>::workerThreadMain() {
continue;
case VerilatedTraceCommand::CHG_BUS:
VL_TRACE_THREAD_DEBUG("Command CHG_BUS");
oldp = (readp++)->oldp;
newBits = (readp++)->newBits;
// Bits stored in bottom byte of command
switch (cmd & 0xFFU) {
case 2: chgBusImpl<2>(oldp, newBits); continue;
case 3: chgBusImpl<3>(oldp, newBits); continue;
case 4: chgBusImpl<4>(oldp, newBits); continue;
case 5: chgBusImpl<5>(oldp, newBits); continue;
case 6: chgBusImpl<6>(oldp, newBits); continue;
case 7: chgBusImpl<7>(oldp, newBits); continue;
case 8: chgBusImpl<8>(oldp, newBits); continue;
case 9: chgBusImpl<9>(oldp, newBits); continue;
case 10: chgBusImpl<10>(oldp, newBits); continue;
case 11: chgBusImpl<11>(oldp, newBits); continue;
case 12: chgBusImpl<12>(oldp, newBits); continue;
case 13: chgBusImpl<13>(oldp, newBits); continue;
case 14: chgBusImpl<14>(oldp, newBits); continue;
case 15: chgBusImpl<15>(oldp, newBits); continue;
case 16: chgBusImpl<16>(oldp, newBits); continue;
case 17: chgBusImpl<17>(oldp, newBits); continue;
case 18: chgBusImpl<18>(oldp, newBits); continue;
case 19: chgBusImpl<19>(oldp, newBits); continue;
case 20: chgBusImpl<20>(oldp, newBits); continue;
case 21: chgBusImpl<21>(oldp, newBits); continue;
case 22: chgBusImpl<22>(oldp, newBits); continue;
case 23: chgBusImpl<23>(oldp, newBits); continue;
case 24: chgBusImpl<24>(oldp, newBits); continue;
case 25: chgBusImpl<25>(oldp, newBits); continue;
case 26: chgBusImpl<26>(oldp, newBits); continue;
case 27: chgBusImpl<27>(oldp, newBits); continue;
case 28: chgBusImpl<28>(oldp, newBits); continue;
case 29: chgBusImpl<29>(oldp, newBits); continue;
case 30: chgBusImpl<30>(oldp, newBits); continue;
case 31: chgBusImpl<31>(oldp, newBits); continue;
case 32: chgBusImpl<32>(oldp, newBits); continue;
}
VL_FATAL_MT(__FILE__, __LINE__, "", "Bad number of bits in CHG_BUS command");
break;
chgBusImpl(readp[0].oldp, readp[1].newBits, cmd & 0xFFULL);
readp += 2;
VL_TRACE_THREAD_DEBUG("Command CHG_BUS DONE");
continue;
case VerilatedTraceCommand::CHG_QUAD:
VL_TRACE_THREAD_DEBUG("Command CHG_QUAD");
// Bits stored in bottom byte of command
chgQuadImpl(readp[0].oldp, readp[1].newBits, cmd & 0xFF);
chgQuadImpl(readp[0].oldp, readp[1].newBits, cmd & 0xFFULL);
readp += 2;
continue;
case VerilatedTraceCommand::CHG_ARRAY:
@@ -516,49 +481,12 @@ template <> void VerilatedTrace<VL_DERIVED_T>::fullBit(vluint32_t* oldp, vluint3
self()->emitBit(oldp - m_sigs_oldvalp, newval);
}
// We want these functions specialized for sizes to avoid hard to predict
// branches, but we don't want them inlined, so we explicitly instantiate the
// template for each size used by Verilator.
template <>
template <int T_Bits>
void VerilatedTrace<VL_DERIVED_T>::fullBus(vluint32_t* oldp, vluint32_t newval) {
void VerilatedTrace<VL_DERIVED_T>::fullBus(vluint32_t* oldp, vluint32_t newval, int bits) {
*oldp = newval;
self()->emitBus<T_Bits>(oldp - m_sigs_oldvalp, newval);
self()->emitBus(oldp - m_sigs_oldvalp, newval, bits);
}
// Note: No specialization for width 1, covered by 'fullBit'
template void VerilatedTrace<VL_DERIVED_T>::fullBus<2>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<3>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<4>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<5>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<6>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<7>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<8>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<9>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<10>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<11>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<12>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<13>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<14>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<15>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<16>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<17>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<18>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<19>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<20>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<21>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<22>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<23>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<24>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<25>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<26>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<27>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<28>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<29>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<30>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<31>(vluint32_t* oldp, vluint32_t newval);
template void VerilatedTrace<VL_DERIVED_T>::fullBus<32>(vluint32_t* oldp, vluint32_t newval);
template <>
void VerilatedTrace<VL_DERIVED_T>::fullQuad(vluint32_t* oldp, vluint64_t newval, int bits) {
*reinterpret_cast<vluint64_t*>(oldp) = newval;