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Optimize additional DFG peephole Shift and Concat patterns (#7077)

This commit is contained in:
Geza Lore 2026-02-14 12:25:17 +00:00 committed by GitHub
parent e0c626e48a
commit a45a058b09
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3 changed files with 85 additions and 0 deletions
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75
src/V3DfgPeephole.cpp
View File

@ -1306,6 +1306,44 @@ class V3DfgPeephole final : public DfgVisitor {
}
}
if (DfgConst* const lConstp = lhsp->cast<DfgConst>()) {
if (DfgCond* const rCondp = rhsp->cast<DfgCond>()) {
if (!rCondp->hasMultipleSinks()) {
DfgVertex* const rtVtxp = rCondp->thenp();
DfgVertex* const reVtxp = rCondp->elsep();
APPLYING(PUSH_CONCAT_THROUGH_COND_LHS) {
DfgConcat* const thenp
= make<DfgConcat>(rtVtxp->fileline(), vtxp->dtype(), lConstp, rtVtxp);
DfgConcat* const elsep
= make<DfgConcat>(reVtxp->fileline(), vtxp->dtype(), lConstp, reVtxp);
DfgCond* const replacementp
= make<DfgCond>(vtxp, rCondp->condp(), thenp, elsep);
replace(vtxp, replacementp);
return;
}
}
}
}
if (DfgConst* const rConstp = rhsp->cast<DfgConst>()) {
if (DfgCond* const lCondp = lhsp->cast<DfgCond>()) {
if (!lCondp->hasMultipleSinks()) {
DfgVertex* const ltVtxp = lCondp->thenp();
DfgVertex* const leVtxp = lCondp->elsep();
APPLYING(PUSH_CONCAT_THROUGH_COND_RHS) {
DfgConcat* const thenp
= make<DfgConcat>(ltVtxp->fileline(), vtxp->dtype(), ltVtxp, rConstp);
DfgConcat* const elsep
= make<DfgConcat>(leVtxp->fileline(), vtxp->dtype(), leVtxp, rConstp);
DfgCond* const replacementp
= make<DfgCond>(vtxp, lCondp->condp(), thenp, elsep);
replace(vtxp, replacementp);
return;
}
}
}
}
// Attempt to narrow a concatenation that produces unused bits on the edges
{
const uint32_t vMsb = vtxp->width() - 1; // MSB of the concatenation
@ -1523,6 +1561,43 @@ class V3DfgPeephole final : public DfgVisitor {
void visit(DfgShiftL* vtxp) override {
if (foldBinary(vtxp)) return;
if (optimizeShiftRHS(vtxp)) return;
DfgVertex* const lhsp = vtxp->lhsp();
DfgVertex* const rhsp = vtxp->rhsp();
if (DfgConst* const rConstp = rhsp->cast<DfgConst>()) {
if (DfgConcat* const lConcatp = lhsp->cast<DfgConcat>()) {
if (!lConcatp->hasMultipleSinks()
&& lConcatp->lhsp()->width() == rConstp->toU32()) {
APPLYING(REPLACE_SHIFTL_CAT) {
DfgConcat* const replacementp = make<DfgConcat>(
vtxp, lConcatp->rhsp(),
makeZero(lConcatp->fileline(), lConcatp->lhsp()->width()));
replace(vtxp, replacementp);
return;
}
}
}
if (DfgShiftR* const lShiftRp = lhsp->cast<DfgShiftR>()) {
if (!lShiftRp->hasMultipleSinks() && isSame(rConstp, lShiftRp->rhsp())) {
if (DfgConcat* const llConcatp = lShiftRp->lhsp()->cast<DfgConcat>()) {
const uint32_t shiftAmount = rConstp->toU32();
if (!llConcatp->hasMultipleSinks()
&& llConcatp->rhsp()->width() == shiftAmount) {
APPLYING(REPLACE_SHIFTRL_CAT) {
DfgConst* const zerop
= makeZero(llConcatp->fileline(), shiftAmount);
DfgConcat* const replacementp
= make<DfgConcat>(vtxp, llConcatp->lhsp(), zerop);
replace(vtxp, replacementp);
return;
}
}
}
}
}
}
}
void visit(DfgShiftR* vtxp) override {

4
src/V3DfgPeepholePatterns.h
View File

@ -40,6 +40,8 @@
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, PUSH_BITWISE_OP_THROUGH_CONCAT) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, PUSH_BITWISE_THROUGH_REDUCTION) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, PUSH_COMPARE_OP_THROUGH_CONCAT) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, PUSH_CONCAT_THROUGH_COND_LHS) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, PUSH_CONCAT_THROUGH_COND_RHS) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, PUSH_CONCAT_THROUGH_NOTS) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, PUSH_NOT_THROUGH_COND) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, PUSH_REDUCTION_THROUGH_CONCAT) \
@ -96,6 +98,8 @@
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, REPLACE_OR_OF_NOT_AND_NOT) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, REPLACE_OR_WITH_ONES) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, REPLACE_SEL_FROM_SEL) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, REPLACE_SHIFTL_CAT) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, REPLACE_SHIFTRL_CAT) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, REPLACE_SUB_WITH_NOT) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, REPLACE_TAUTOLOGICAL_OR) \
_FOR_EACH_DFG_PEEPHOLE_OPTIMIZATION_APPLY(macro, REPLACE_TAUTOLOGICAL_OR_3) \

6
test_regress/t/t_dfg_peephole.v
View File

@ -245,6 +245,12 @@ module t (
end
`signal(PUSH_SEL_THROUGH_SPLICE, sel_from_partial_tmp[1:0]);
`signal(PUSH_CONCAT_THROUGH_COND_LHS, {5'd0, rand_a[0] ? {rand_b[4], 1'b0} : {1'b0, rand_b[6]}});
`signal(PUSH_CONCAT_THROUGH_COND_RHS, {rand_a[0] ? {rand_b[5], 1'b0} : {1'b0, rand_b[7]}, 5'd0});
`signal(REPLACE_SHIFTL_CAT, {31'd0, rand_a[42 +: 7]} << 31);
`signal(REPLACE_SHIFTRL_CAT, {rand_a[13 +: 7], rand_b[8 +: 27]} >> 27 << 27);
// Asscending ranges
`signal(ASCENDNG_SEL, arand_a[0:4]);
// verilator lint_off ASCRANGE