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[tools/bgpgrep] Make filter bytecode generation smarter, take advantage of new optimization opportunities

This commit is contained in:
Lorenzo Cogotti 2021-10-18 12:15:32 +02:00
parent ae052ea987
commit ef77abb25a
1 changed files with 64 additions and 56 deletions
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116
tools/bgpgrep/bgpgrep_compile.c
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@ -314,7 +314,7 @@ static Expridx GetTerm(void)
Sint32 kidx = BgpgrepC_BakeAsRegexp();
c[n++] = BGP_VMOP(BGP_VMOP_LOADK, kidx);
c[n++] = BGP_VMOP_FASMTC;
c[n++] = BGP_VMOP_ASMTCH;
return PushLeaf(c, n);
} else if (strcmp(C.curterm, "-peer") == 0) {
@ -468,18 +468,15 @@ static Expropc BgpgrepC_CompileRecurse(Expridx idx, Expropc opc)
Bgp_VmEmit(&S.vm, BGP_VMOP_BLK);
BgpgrepC_CompileRecurse(op->n.l, op->opc);
if (C.code[op->n.l].opc != OP_AND) {
Bgp_VmEmit(&S.vm, BGP_VMOP_NOT);
Bgp_VmEmit(&S.vm, BGP_VMOP_CFAIL);
}
if (C.code[op->n.l].opc != OP_AND)
Bgp_VmEmit(&S.vm, BGP_VMOP_ORFAIL);
BgpgrepC_CompileRecurse(op->n.r, op->opc);
if (C.code[op->n.r].opc != OP_AND) {
Bgp_VmEmit(&S.vm, BGP_VMOP_NOT);
Bgp_VmEmit(&S.vm, BGP_VMOP_CFAIL);
}
if (C.code[op->n.r].opc != OP_AND)
Bgp_VmEmit(&S.vm, BGP_VMOP_ORFAIL);
if (nestedBlock) {
Bgp_VmEmit(&S.vm, BGP_VMOP(BGP_VMOP_LOADU, TRUE));
Bgp_VmEmit(&S.vm, BGP_VMOP_CPASS);
Bgp_VmEmit(&S.vm, BGP_VMOP_ENDBLK);
}
break;
@ -498,8 +495,7 @@ static Expropc BgpgrepC_CompileRecurse(Expridx idx, Expropc opc)
Bgp_VmEmit(&S.vm, BGP_VMOP_CPASS);
if (nestedBlock) {
Bgp_VmEmit(&S.vm, BGP_VMOP(BGP_VMOP_LOADU, TRUE));
Bgp_VmEmit(&S.vm, BGP_VMOP_CFAIL);
Bgp_VmEmit(&S.vm, BGP_VMOP(BGP_VMOP_LOADU, FALSE));
Bgp_VmEmit(&S.vm, BGP_VMOP_ENDBLK);
}
break;
@ -531,16 +527,11 @@ static void BgpgrepC_Compile(Expridx startIdx)
Bgp_VmEmit(&S.vm, BGP_VMOP(BGP_VMOP_LOADU, TRUE));
Bgp_VmEmit(&S.vm, BGP_VMOP_CFAIL);
break;
case OP_AND:
Bgp_VmEmit(&S.vm, BGP_VMOP(BGP_VMOP_LOADU, TRUE));
Bgp_VmEmit(&S.vm, BGP_VMOP_CPASS);
case OP_AND: // Good as it is
break;
case OP_NOT:
case OP_LEAF:
Bgp_VmEmit(&S.vm, BGP_VMOP_CPASS);
Bgp_VmEmit(&S.vm, BGP_VMOP(BGP_VMOP_LOADU, TRUE));
Bgp_VmEmit(&S.vm, BGP_VMOP_CFAIL);
Bgp_VmEmit(&S.vm, BGP_VMOP_ORFAIL);
break;
default: UNREACHABLE; break;
@ -575,7 +566,7 @@ static void BgpgrepC_Optimize(void)
Boolean changed;
i = 0;
while (i < S.vm.progLen) { // NOTE: don't care for END
while (i <= S.vm.progLen) { // NOTE: Take END into account
if (S.vm.prog[i] == BGP_VMOP_NOP) {
// Skip initial NOPs
i++;
@ -586,7 +577,7 @@ static void BgpgrepC_Optimize(void)
// Fill peephole window
for (j = 0, n = 0; n < ARRAY_SIZE(w); j++) {
if (i + j >= S.vm.progLen) // NOTE: don't care for END
if (i + j > S.vm.progLen) // NOTE: Take END into account
break;
if (S.vm.prog[i+j] == BGP_VMOP_NOP)
continue; // do not place any NOP inside window
@ -597,7 +588,7 @@ static void BgpgrepC_Optimize(void)
}
// Trivial redundant operation elimination
for (j = 1; j < n; j++) {
for (j = 1; j < n; j++) { // 2-instruction checks
// NOT-NOT = NOP
if (w[j] == BGP_VMOP_NOT && w[j-1] == BGP_VMOP_NOT) {
w[j-1] = w[j] = BGP_VMOP_NOP;
@ -621,39 +612,59 @@ static void BgpgrepC_Optimize(void)
changed = TRUE;
continue;
}
// NOT-CFAIL = ORFAIL
if (w[j-1] == BGP_VMOP_NOT && w[j] == BGP_VMOP_CFAIL) {
w[j-1] = BGP_VMOP_NOP;
w[j] = BGP_VMOP_ORFAIL;
changed = TRUE;
continue;
}
if (n == 4) {
// Simplify common CFAIL and CPASS chains introduced by AND/OR blocks
static const Bgpvmbytec ncfncp[] = {
BGP_VMOP_NOT,
BGP_VMOP_CFAIL,
BGP_VMOP(BGP_VMOP_LOADU, TRUE),
BGP_VMOP_CPASS
};
static const Bgpvmbytec ncpncf[] = {
BGP_VMOP_NOT,
BGP_VMOP_CPASS,
BGP_VMOP(BGP_VMOP_LOADU, TRUE),
BGP_VMOP_CFAIL
};
if (memcmp(w, ncfncp, sizeof(ncfncp)) == 0) {
// Move CPASS up
w[0] = BGP_VMOP_NOP;
w[1] = BGP_VMOP_CPASS;
w[2] = BGP_VMOP(BGP_VMOP_LOADU, TRUE);
w[3] = BGP_VMOP_CFAIL;
// NOT-CPASS = ORPASS
if (w[j-1] == BGP_VMOP_NOT && w[j] == BGP_VMOP_CPASS) {
w[j-1] = BGP_VMOP_NOP;
w[j] = BGP_VMOP_ORPASS;
changed = TRUE;
} else if (memcmp(w, ncpncf, sizeof(ncpncf)) == 0) {
// Move CFAIL up
w[0] = BGP_VMOP_NOP;
w[1] = BGP_VMOP_CFAIL;
w[2] = BGP_VMOP(BGP_VMOP_LOADU, TRUE);
w[3] = BGP_VMOP_CPASS;
continue;
}
// NOT-ORFAIL = CFAIL
if (w[j-1] == BGP_VMOP_NOT && w[j] == BGP_VMOP_ORFAIL) {
w[j-1] = BGP_VMOP_NOP;
w[j] = BGP_VMOP_CFAIL;
changed = TRUE;
continue;
}
// NOT-ORPASS = CPASS
if (w[j-1] == BGP_VMOP_NOT && w[j] == BGP_VMOP_ORPASS) {
w[j-1] = BGP_VMOP_NOP;
w[j] = BGP_VMOP_CPASS;
changed = TRUE;
continue;
}
// [NON-BREAKING,NON-ENDING]-END = NOP-END
if (!BGP_ISVMOPBREAKING(w[j-1]) && !BGP_ISVMOPENDING(w[j-1]) && w[j] == BGP_VMOP_END) {
w[j-1] = BGP_VMOP_NOP;
changed = TRUE;
continue;
}
}
for (j = 3; j < n; j++) { // 4-instruction checks
// CPASS-LOADU(T)-CFAIL-<ENDING> = ORFAIL-LOADU(T)-<ENDING>
// Leftover by OR chains
if (w[j-3] == BGP_VMOP_CPASS &&
IsLoadNz(w[j-2]) &&
w[j-1] == BGP_VMOP_CFAIL &&
BGP_ISVMOPENDING(w[j])) {
w[j-3] = BGP_VMOP_NOP;
w[j-2] = BGP_VMOP_ORFAIL;
w[j-1] = BGP_VMOP(BGP_VMOP_LOADU, TRUE);
changed = TRUE;
continue;
}
}
@ -735,7 +746,7 @@ void Bgpgrep_CompileVmProgram(int argc, char **argv)
if (tok)
Bgpgrep_Fatal("Unexpected '%s' after '%s'", tok, last);
else // should never happen but still...
else
Bgpgrep_Fatal("Unexpected match expression end after '%s'", last);
}
@ -744,9 +755,6 @@ void Bgpgrep_CompileVmProgram(int argc, char **argv)
BgpgrepC_Optimize();
} else {
// Trivial filter
Bgp_VmEmit(&S.vm, BGP_VMOP(BGP_VMOP_LOADU, TRUE));
Bgp_VmEmit(&S.vm, BGP_VMOP_CPASS);
S.isTrivialFilter = TRUE;
}
if (S.dumpBytecode)