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Allow mismatched widths in operands of shifts in DFG

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Fixes #3872.

Testing this is a bit tricky, as the front-end fixes up the operand
widths in shifts to match, and we need V3Const to introduce a mismatched
one by reducing `4'd2 ** x` (with x being 2 2-bit wide signal) to `4'd1
<< x`, but t_dfg_peephole runs with V3Const disabled exactly because it
makes it hard to write tests. Rather than fixing this one case in
V3Const (which we should do systematically at some point), I fixed DFG
to accept these just in case V3Const generates more of them. The
assertions were there only because of paranoia (as I thought these were
not possible inputs), the code otherwise works.
This commit is contained in:
Geza Lore
2023-01-22 10:55:03 +00:00
parent 3a8288b0f6
commit 3069860fdf
5 changed files with 43 additions and 10 deletions
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src/V3DfgPeephole.cpp
-9
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@@ -1400,26 +1400,17 @@ class V3DfgPeephole final : public DfgVisitor {
}
void visit(DfgShiftL* vtxp) override {
UASSERT_OBJ(vtxp->dtypep() == vtxp->lhsp()->dtypep(), vtxp, "Mismatched width");
if (foldBinary(vtxp)) return;
optimizeShiftRHS(vtxp);
}
void visit(DfgShiftR* vtxp) override {
UASSERT_OBJ(vtxp->dtypep() == vtxp->lhsp()->dtypep(), vtxp, "Mismatched width");
if (foldBinary(vtxp)) return;
optimizeShiftRHS(vtxp);
}
void visit(DfgShiftRS* vtxp) override {
UASSERT_OBJ(vtxp->dtypep() == vtxp->lhsp()->dtypep(), vtxp, "Mismatched width");
if (foldBinary(vtxp)) return;
optimizeShiftRHS(vtxp);
}