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DFG: Special case representation of AstSel

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AstSel is a ternary node, but the 'widthp' is always constant and is
hence redundant, and 'lsbp' is very often constant. As AstSel is fairly
common, we special case as a DfgSel for the constant 'lsbp', and as
'DfgMux` for the non-constant 'lsbp'.
This commit is contained in:
Geza Lore
2022-10-06 19:59:01 +01:00
parent 0570cb8d9f
commit 29a080dd9b
5 changed files with 309 additions and 284 deletions
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src/V3DfgAstToDfg.cpp
+32 -6
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@@ -187,15 +187,12 @@ class AstToDfgVisitor final : public VNVisitor {
if (AstConcat* const concatp = VN_CAST(nodep, Concat)) {
AstNode* const lhsp = concatp->lhsp();
AstNode* const rhsp = concatp->rhsp();
const uint32_t lWidth = lhsp->width();
const uint32_t rWidth = rhsp->width();
{
FileLine* const lFlp = lhsp->fileline();
DfgSel* const lVtxp = new DfgSel{*m_dfgp, lFlp, DfgVertex::dtypeFor(lhsp)};
lVtxp->fromp(vtxp);
lVtxp->lsbp(new DfgConst{*m_dfgp, new AstConst{lFlp, rWidth}});
lVtxp->widthp(new DfgConst{*m_dfgp, new AstConst{lFlp, lWidth}});
lVtxp->lsb(rhsp->width());
if (!convertAssignment(flp, lhsp, lVtxp)) return false;
}
@@ -203,8 +200,7 @@ class AstToDfgVisitor final : public VNVisitor {
FileLine* const rFlp = rhsp->fileline();
DfgSel* const rVtxp = new DfgSel{*m_dfgp, rFlp, DfgVertex::dtypeFor(rhsp)};
rVtxp->fromp(vtxp);
rVtxp->lsbp(new DfgConst{*m_dfgp, new AstConst{rFlp, 0u}});
rVtxp->widthp(new DfgConst{*m_dfgp, new AstConst{rFlp, rWidth}});
rVtxp->lsb(0);
return convertAssignment(flp, rhsp, rVtxp);
}
}
@@ -467,6 +463,36 @@ class AstToDfgVisitor final : public VNVisitor {
nodep->user1p(vtxp);
}
void visit(AstSel* nodep) override {
UASSERT_OBJ(!nodep->user1p(), nodep, "Already has Dfg vertex");
if (unhandled(nodep)) return;
if (!VN_IS(nodep->widthp(), Const)) { // This should never be taken, but paranoia
m_foundUnhandled = true;
++m_ctx.m_nonRepNode;
return;
}
iterate(nodep->fromp());
if (m_foundUnhandled) return;
FileLine* const flp = nodep->fileline();
DfgVertex* vtxp = nullptr;
if (AstConst* const constp = VN_CAST(nodep->lsbp(), Const)) {
DfgSel* const selp = new DfgSel{*m_dfgp, flp, DfgVertex::dtypeFor(nodep)};
selp->fromp(nodep->fromp()->user1u().to<DfgVertex*>());
selp->lsb(constp->toUInt());
vtxp = selp;
} else {
iterate(nodep->lsbp());
if (m_foundUnhandled) return;
DfgMux* const muxp = new DfgMux{*m_dfgp, flp, DfgVertex::dtypeFor(nodep)};
muxp->fromp(nodep->fromp()->user1u().to<DfgVertex*>());
muxp->lsbp(nodep->lsbp()->user1u().to<DfgVertex*>());
vtxp = muxp;
}
m_uncommittedVertices.push_back(vtxp);
nodep->user1p(vtxp);
}
// The rest of the 'visit' methods are generated by 'astgen'
#include "V3Dfg__gen_ast_to_dfg.h"