From b62d74a055975f7bd7b57d3bd3cffdd001331e57 Mon Sep 17 00:00:00 2001 From: Geza Lore Date: Fri, 19 Jun 2026 17:33:50 +0100 Subject: [PATCH] Add Dfg cycle breaking support --- src/V3DfgBreakCycles.cpp | 52 +++++++++++++++--- test_regress/t/t_dfg_break_cycles.v | 82 +++++++++++++++++++++++++++++ 2 files changed, 128 insertions(+), 6 deletions(-) diff --git a/src/V3DfgBreakCycles.cpp b/src/V3DfgBreakCycles.cpp index 73789cb9b..ecdcc875d 100644 --- a/src/V3DfgBreakCycles.cpp +++ b/src/V3DfgBreakCycles.cpp @@ -332,12 +332,25 @@ class TraceDriver final : public DfgVisitor { } void visit(DfgArraySel* vtxp) override { - // Only constant select - const DfgConst* const idxp = vtxp->bitp()->cast(); - if (!idxp) return; // From a variable const DfgVarArray* varp = vtxp->fromp()->cast(); if (!varp) return; + + // If index is not constant, independence was proven only if the 'fromp' is + // independent, so no need to trace that + if (!vtxp->bitp()->is()) { + DfgArraySel* const resp = make(vtxp, vtxp->width()); + resp->fromp(vtxp->fromp()); + resp->bitp(trace(vtxp->bitp(), vtxp->bitp()->width() - 1, 0)); + DfgSel* const selp = make(vtxp, m_msb - m_lsb + 1); + selp->fromp(resp); + selp->lsb(m_lsb); + SET_RESULT(selp); + return; + } + + // Trace the relevant driver based on the static index + const DfgConst* const idxp = vtxp->bitp()->as(); UASSERT_OBJ(!varp->isVolatile(), vtxp, "Should not trace through volatile VarArray"); // Skip through intermediate variables while (varp->srcp() && varp->srcp()->is()) { @@ -589,6 +602,16 @@ class TraceDriver final : public DfgVisitor { SET_RESULT(resp); } + void visit(DfgMatchMasked* vtxp) override { + DfgMatchMasked* const resp = make(vtxp, vtxp->width()); + resp->lhsp(trace(vtxp->lhsp(), vtxp->lhsp()->width() - 1, 0)); + resp->matchp(trace(vtxp->matchp(), vtxp->matchp()->width() - 1, 0)); + DfgSel* const selp = make(vtxp, m_msb - m_lsb + 1); + selp->fromp(resp); + selp->lsb(m_lsb); + SET_RESULT(resp); + } + #undef SET_RESULT public: @@ -721,12 +744,23 @@ class IndependentBits final : public DfgVisitor { } void visit(DfgArraySel* vtxp) override { - // Only constant select - const DfgConst* const idxp = vtxp->bitp()->cast(); - if (!idxp) return; // From a variable const DfgVarArray* varp = vtxp->fromp()->cast(); if (!varp) return; + + // If index is not constant, independent only if the variable index + // is indenpendent and the array is independent. We don't track arrays, + // so we will assume an array is only independent if it has no drivers + // in the graph. TODO: could check all drivers. + if (!vtxp->bitp()->is()) { + if (MASK(vtxp->bitp()).isEqAllOnes() && !varp->srcp() && !varp->defaultp()) { + MASK(vtxp).setAllBits1(); + } + return; + } + + // Trace the relevant driver based on the static index + const DfgConst* const idxp = vtxp->bitp()->as(); // We cannot trace through a volatile variable, so pretend all bits are dependent if (varp->isVolatile()) return; // Skip through intermediate variables @@ -954,6 +988,12 @@ class IndependentBits final : public DfgVisitor { } } + void visit(DfgMatchMasked* vtxp) override { + if (MASK(vtxp->lhsp()).isEqAllOnes() && MASK(vtxp->matchp()).isEqAllOnes()) { // + MASK(vtxp).setAllBits1(); + } + } + #undef MASK // Enqueue sinks of vertex to work list for traversal - only called from constructor diff --git a/test_regress/t/t_dfg_break_cycles.v b/test_regress/t/t_dfg_break_cycles.v index 80c5aad04..ae7e6d781 100644 --- a/test_regress/t/t_dfg_break_cycles.v +++ b/test_regress/t/t_dfg_break_cycles.v @@ -436,4 +436,86 @@ module t ( assign VOLATILE_ARRAY_IN_CYCLE_1 = volatile_array_in_cycle_1a[1]; // verilator lint_on + ////////////////////////////////////////////////////////////////////////// + // Match masked + ////////////////////////////////////////////////////////////////////////// + + logic [63:0] match_masked; // UNOPTFLAT + always_comb begin + casez (rand_a[31:0]) + 32'b????????_????????_????????_???????1 : match_masked[31:0] = 32'd00; + 32'b????????_????????_????????_??????1? : match_masked[31:0] = 32'd01; + 32'b????????_????????_????????_?????1?? : match_masked[31:0] = 32'd02; + 32'b????????_????????_????????_????1??? : match_masked[31:0] = 32'd03; + 32'b????????_????????_????????_???1???? : match_masked[31:0] = 32'd04; + 32'b????????_????????_????????_??1????? : match_masked[31:0] = 32'd05; + 32'b????????_????????_????????_?1?????? : match_masked[31:0] = 32'd06; + 32'b????????_????????_????????_1??????? : match_masked[31:0] = 32'd07; + 32'b????????_????????_???????1_???????? : match_masked[31:0] = 32'd08; + 32'b????????_????????_??????1?_???????? : match_masked[31:0] = 32'd09; + 32'b????????_????????_?????1??_???????? : match_masked[31:0] = 32'd10; + 32'b????????_????????_????1???_???????? : match_masked[31:0] = 32'd11; + 32'b????????_????????_???1????_???????? : match_masked[31:0] = 32'd12; + 32'b????????_????????_??1?????_???????? : match_masked[31:0] = 32'd13; + 32'b????????_????????_?1??????_???????? : match_masked[31:0] = 32'd14; + 32'b????????_????????_1???????_???????? : match_masked[31:0] = 32'd15; + 32'b????????_???????1_????????_???????? : match_masked[31:0] = 32'd16; + 32'b????????_??????1?_????????_???????? : match_masked[31:0] = 32'd17; + 32'b????????_?????1??_????????_???????? : match_masked[31:0] = 32'd18; + 32'b????????_????1???_????????_???????? : match_masked[31:0] = 32'd19; + 32'b????????_???1????_????????_???????? : match_masked[31:0] = 32'd20; + 32'b????????_??1?????_????????_???????? : match_masked[31:0] = 32'd21; + 32'b????????_?1??????_????????_???????? : match_masked[31:0] = 32'd22; + 32'b????????_1???????_????????_???????? : match_masked[31:0] = 32'd23; + 32'b???????1_????????_????????_???????? : match_masked[31:0] = 32'd24; + 32'b??????1?_????????_????????_???????? : match_masked[31:0] = 32'd25; + 32'b?????1??_????????_????????_???????? : match_masked[31:0] = 32'd26; + 32'b????1???_????????_????????_???????? : match_masked[31:0] = 32'd27; + 32'b???1????_????????_????????_???????? : match_masked[31:0] = 32'd28; + 32'b??1?????_????????_????????_???????? : match_masked[31:0] = 32'd29; + 32'b?1??????_????????_????????_???????? : match_masked[31:0] = 32'd30; + 32'b1???????_????????_????????_???????? : match_masked[31:0] = 32'd31; + default : match_masked[31:0] = '1; + endcase + end + always_comb begin + casez (match_masked[31:0]) + 32'd00 : match_masked[63:32] = 32'b00000000_00000000_00000000_00000001; + 32'd01 : match_masked[63:32] = 32'b00000000_00000000_00000000_00000010; + 32'd02 : match_masked[63:32] = 32'b00000000_00000000_00000000_00000100; + 32'd03 : match_masked[63:32] = 32'b00000000_00000000_00000000_00001000; + 32'd04 : match_masked[63:32] = 32'b00000000_00000000_00000000_00010000; + 32'd05 : match_masked[63:32] = 32'b00000000_00000000_00000000_00100000; + 32'd06 : match_masked[63:32] = 32'b00000000_00000000_00000000_01000000; + 32'd07 : match_masked[63:32] = 32'b00000000_00000000_00000000_10000000; + 32'd08 : match_masked[63:32] = 32'b00000000_00000000_00000001_00000000; + 32'd09 : match_masked[63:32] = 32'b00000000_00000000_00000010_00000000; + 32'd10 : match_masked[63:32] = 32'b00000000_00000000_00000100_00000000; + 32'd11 : match_masked[63:32] = 32'b00000000_00000000_00001000_00000000; + 32'd12 : match_masked[63:32] = 32'b00000000_00000000_00010000_00000000; + 32'd13 : match_masked[63:32] = 32'b00000000_00000000_00100000_00000000; + 32'd14 : match_masked[63:32] = 32'b00000000_00000000_01000000_00000000; + 32'd15 : match_masked[63:32] = 32'b00000000_00000000_10000000_00000000; + 32'd16 : match_masked[63:32] = 32'b00000000_00000001_00000000_00000000; + 32'd17 : match_masked[63:32] = 32'b00000000_00000010_00000000_00000000; + 32'd18 : match_masked[63:32] = 32'b00000000_00000100_00000000_00000000; + 32'd19 : match_masked[63:32] = 32'b00000000_00001000_00000000_00000000; + 32'd20 : match_masked[63:32] = 32'b00000000_00010000_00000000_00000000; + 32'd21 : match_masked[63:32] = 32'b00000000_00100000_00000000_00000000; + 32'd22 : match_masked[63:32] = 32'b00000000_01000000_00000000_00000000; + 32'd23 : match_masked[63:32] = 32'b00000000_10000000_00000000_00000000; + 32'd24 : match_masked[63:32] = 32'b00000001_00000000_00000000_00000000; + 32'd25 : match_masked[63:32] = 32'b00000010_00000000_00000000_00000000; + 32'd26 : match_masked[63:32] = 32'b00000100_00000000_00000000_00000000; + 32'd27 : match_masked[63:32] = 32'b00001000_00000000_00000000_00000000; + 32'd28 : match_masked[63:32] = 32'b00010000_00000000_00000000_00000000; + 32'd29 : match_masked[63:32] = 32'b00100000_00000000_00000000_00000000; + 32'd30 : match_masked[63:32] = 32'b01000000_00000000_00000000_00000000; + 32'd31 : match_masked[63:32] = 32'b10000000_00000000_00000000_00000000; + default: match_masked[63:32] = 32'b00000000_00000000_00000000_00000000; + endcase + end + `signal(MATCH_MASKED, 64); + assign MATCH_MASKED = match_masked; + endmodule