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DfgPeephole: Further restrict PUSH_REDUCTION_THROUGH_CONCAT 

Only apply when there is guaranteed to be a subsequent constant folding
and elimination of some of the expression, otherwise this sometimes
interferes with the simplification of concatenations and harms overall
performance.
This commit is contained in:
Geza Lore 2022-10-05 22:54:36 +01:00
parent 1a8188e1b4
commit 22fcd616aa
2 changed files with 11 additions and 10 deletions
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9
src/V3DfgPeephole.cpp
View File

@ -415,12 +415,12 @@ class V3DfgPeephole final : public DfgVisitor {
}
if (DfgConcat* const concatp = srcp->cast<DfgConcat>()) {
if (!concatp->hasMultipleSinks()) {
if (concatp->lhsp()->is<DfgConst>() || concatp->rhsp()->is<DfgConst>()) {
APPLYING(PUSH_REDUCTION_THROUGH_CONCAT) {
// Reduce the parts of the concatenation
Reduction* const lRedp = new Reduction{m_dfg, srcp->fileline(), m_bitDType};
Reduction* const lRedp = new Reduction{m_dfg, concatp->fileline(), m_bitDType};
lRedp->srcp(concatp->lhsp());
Reduction* const rRedp = new Reduction{m_dfg, srcp->fileline(), m_bitDType};
Reduction* const rRedp = new Reduction{m_dfg, concatp->fileline(), m_bitDType};
rRedp->srcp(concatp->rhsp());
// Bitwise reduce the results
@ -429,9 +429,10 @@ class V3DfgPeephole final : public DfgVisitor {
replacementp->rhsp(rRedp);
vtxp->replaceWith(replacementp);
// Optimize the new reductions
// Optimize the new terms
optimizeReduction(lRedp);
optimizeReduction(rRedp);
iterate(replacementp);
return;
}
}

12
test_regress/t/t_dfg_peephole.v
View File

@ -149,12 +149,12 @@ module t (
`signal(PUSH_BITWISE_THROUGH_REDUCTION_AND, (&(rand_a + 64'd105)) & (&(rand_b + 64'd108)));
`signal(PUSH_BITWISE_THROUGH_REDUCTION_OR, (|(rand_a + 64'd106)) | (|(rand_b + 64'd109)));
`signal(PUSH_BITWISE_THROUGH_REDUCTION_XOR, (^(rand_a + 64'd107)) ^ (^(rand_b + 64'd110)));
`signal(PUSH_REDUCTION_THROUGH_CONCAT_AND, &{(rand_a + 64'd102), rand_b});
`signal(PUSH_REDUCTION_THROUGH_CONCAT_OR, |{(rand_a + 64'd103), rand_b});
`signal(PUSH_REDUCTION_THROUGH_CONCAT_XOR, ^{(rand_a + 64'd104), rand_b});
`signal(REMOVE_WIDTH_ONE_REDUCTION_AND, &{randbit_a ^ rand_a[0], rand_b});
`signal(REMOVE_WIDTH_ONE_REDUCTION_OR, |{randbit_a ^ rand_a[1], rand_b});
`signal(REMOVE_WIDTH_ONE_REDUCTION_XOR, ^{randbit_a ^ rand_a[2], rand_b});
`signal(PUSH_REDUCTION_THROUGH_CONCAT_AND, &{1'd1, rand_b});
`signal(PUSH_REDUCTION_THROUGH_CONCAT_OR, |{1'd1, rand_b});
`signal(PUSH_REDUCTION_THROUGH_CONCAT_XOR, ^{1'd1, rand_b});
`signal(REMOVE_WIDTH_ONE_REDUCTION_AND, &rand_a[0]);
`signal(REMOVE_WIDTH_ONE_REDUCTION_OR, |rand_a[0]);
`signal(REMOVE_WIDTH_ONE_REDUCTION_XOR, ^rand_a[0]);
`signal(REMOVE_XOR_WITH_ZERO, 64'd0 ^ rand_a);
`signal(REMOVE_XOR_WITH_ONES, -64'd1 ^ rand_a);
`signal(REPLACE_COND_DEC, randbit_a ? rand_b - 64'b1 : rand_b);