Exclude non-simple wide expressions

Signed-off-by: Bartłomiej Chmiel <[email protected]>

src/V3Gate.cpp

@@ -684,7 +684,14 @@ class GateInline final {
     size_t m_statExcluded = 0;  // Statistic tracking
 
     // METHODS
-    static bool excludedWide(GateVarVertex* const vVtxp) {
+    static bool isCheapWide(const GateLogicVertex* const lVtxp, const AstNodeExpr* const rhsp) {
+        if (const AstSel* const selp = VN_CAST(rhsp, Sel)) {
+            if (selp->lsbConst() % VL_EDATASIZE == 0) return true;
+        }
+        return lVtxp->slow() || VN_IS(rhsp, NodeVarRef) || VN_IS(rhsp, Const)
+               || VN_IS(rhsp, ArraySel);
+    }
+    static bool excludedWide(GateVarVertex* const vVtxp, const AstNodeExpr* const rhsp) {
         // Handle wides with logic drivers.
         if (!vVtxp->varScp()->isWide() || vVtxp->inEmpty()
             || vVtxp->varScp()->widthWords() <= v3Global.opt.expandLimit())
@@ -693,8 +700,7 @@ class GateInline final {
         const GateLogicVertex* const lVtxp
             = vVtxp->inEdges().frontp()->fromp()->as<GateLogicVertex>();
 
-        if (lVtxp->slow() || VN_IS(lVtxp->nodep(), AssignAlias))
-            return false;  // Do not optimize consts, aliases and slow parts.
+        if (isCheapWide(lVtxp, rhsp)) return false;
 
         // Exclude from inlining variables READ multiple times that are initialized by wide
         // assigns.
@@ -790,12 +796,6 @@ class GateInline final {
 
             // Can't inline if non-reducible, etc
             if (!vVtxp->reducible()) continue;
-            if (excludedWide(vVtxp)) {
-                ++m_statExcluded;
-                UINFO(9, "Gate inline exclude '" << vVtxp->name() << "'" << endl);
-                vVtxp->clearReducible("Excluded wide");  // Check once.
-                continue;
-            }
 
             // Grab the driving logic
             GateLogicVertex* const lVtxp
@@ -813,6 +813,12 @@ class GateInline final {
             if (!okVisitor.isSimple()) continue;
             // If the varScope is already removed from logicp, no need to try substitution.
             if (!okVisitor.varAssigned(vVtxp->varScp())) continue;
+            if (excludedWide(vVtxp, okVisitor.substitutionp())) {
+                ++m_statExcluded;
+                UINFO(9, "Gate inline exclude '" << vVtxp->name() << "'" << endl);
+                vVtxp->clearReducible("Excluded wide");  // Check once.
+                continue;
+            }
 
             // Does it read multiple source variables?
             if (okVisitor.readVscps().size() > 1) {

test_regress/t/t_duplicate_wide_expr.py → test_regress/t/t_gate_inline_wide_exclude_multiple.py

@@ -11,9 +11,9 @@
 
 test.scenarios('vlt')
 
-test.compile(verilator_flags2=['--stats', '--expand-limit 5'])
+test.lint(verilator_flags2=['--stats', '--expand-limit 5'])
 
-test.file_grep(test.stats, r'Optimizations, Gate excluded wide expressions\s+(\d+)', 3)
-test.file_grep(test.stats, r'Optimizations, expand wides\s+(\d+)', 162)
+test.file_grep(test.stats, r'Optimizations, Gate excluded wide expressions\s+(\d+)', 2)
+test.file_grep(test.stats, r'Optimizations, Gate sigs deleted\s+(\d+)', 4)
 
 test.passes()

test_regress/t/t_gate_inline_wide_exclude_multiple.v

@@ -0,0 +1,27 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Antmicro.
+// SPDX-License-Identifier: CC0-1.0
+
+localparam N = 256; // Wider than expand limit.
+
+module t(
+   input wire [N-1:0] i,
+   output logic [N-1:0] o_multiple1,
+   output logic [N-1:0] o_multiple2,
+   output wire [N-1:0] o
+   );
+
+   // Exclude from inline wide expressions referenced multiple times.
+   wire [N-1:0] wide_multiple_assigns = N >> i;
+   wire [N-1:0] wide = N << i;
+
+   for (genvar n = 0; n < N - 1; ++n) begin
+      assign o[n] = i[N-1-n] | wide[N-1-n];
+   end
+
+   assign o_multiple1 = wide_multiple_assigns | i + 1;
+   assign o_multiple2 = wide_multiple_assigns | i + 2;
+endmodule
+

test_regress/t/t_gate_inline_wide_noexclude_arraysel.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('vlt')
+
+test.lint(verilator_flags2=['--stats', '--expand-limit 5'])
+
+test.file_grep(test.stats, r'Optimizations, Gate excluded wide expressions\s+(\d+)', 0)
+test.file_grep(test.stats, r'Optimizations, Gate sigs deleted\s+(\d+)', 1)
+
+test.passes()

test_regress/t/t_gate_inline_wide_noexclude_arraysel.v

@@ -0,0 +1,20 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Antmicro.
+// SPDX-License-Identifier: CC0-1.0
+
+module t;
+   logic [255:0] arrd [0:0] = '{ 1 };
+   logic [255:0] y0;
+
+   // Do not exclude from inlining wide arraysels.
+   always_comb y0 = arrd[0];
+
+   always_comb begin
+     if (y0 != 1 && y0 != 0) begin
+       $stop;
+     end
+   end
+endmodule
+

test_regress/t/t_gate_inline_wide_noexclude_const.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('vlt')
+
+test.lint(verilator_flags2=['--stats', '--expand-limit 5'])
+
+test.file_grep(test.stats, r'Optimizations, Gate excluded wide expressions\s+(\d+)', 0)
+test.file_grep(test.stats, r'Optimizations, Gate sigs deleted\s+(\d+)', 2)
+
+test.passes()

test_regress/t/t_gate_inline_wide_noexclude_const.v

@@ -0,0 +1,20 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Antmicro.
+// SPDX-License-Identifier: CC0-1.0
+
+module t;
+   logic [255:0] arrd = 256'b0;
+   logic [255:0] y0;
+
+   // Do not exclude from inlining wide variables with const assignments.
+   always_comb y0 = 256'(arrd[0]);
+
+   always_comb begin
+     if (y0 != 1 && y0 != 0) begin
+       $stop;
+     end
+   end
+endmodule
+

test_regress/t/t_gate_inline_wide_noexclude_other_scope.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('vlt')
+
+test.lint(verilator_flags2=['--stats', '--expand-limit 5'])
+
+test.file_grep(test.stats, r'Optimizations, Gate excluded wide expressions\s+(\d+)', 0)
+
+test.passes()

test_regress/t/t_gate_inline_wide_noexclude_other_scope.v

@@ -0,0 +1,26 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Antmicro.
+// SPDX-License-Identifier: CC0-1.0
+
+localparam N = 256; // Wider than expand limit.
+
+module t(
+   input wire [N-1:0] i,
+   output wire [N-1:0] o
+   );
+
+   // Do not exclude from inlining wides referenced in different scope.
+   wire [N-1:0] wide = N ~^ i;
+
+   sub sub(i, wide, o);
+endmodule
+
+module sub(input wire [N-1:0] i, input wire [N-1:0] wide, output logic [N-1:0] o);
+   initial begin
+      for (integer n = 0; n < N ; ++n) begin
+         o[n] = i[N-1-n] | wide[N-1-n];
+      end
+   end
+endmodule

test_regress/t/t_gate_inline_wide_noexclude_sel.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('vlt')
+
+test.lint(verilator_flags2=['--stats', '--expand-limit 5'])
+
+test.file_grep(test.stats, r'Optimizations, Gate excluded wide expressions\s+(\d+)', 1)
+test.file_grep(test.stats, r'Optimizations, Gate sigs deleted\s+(\d+)', 9)
+
+test.passes()

test_regress/t/t_gate_inline_wide_noexclude_sel.v

@@ -0,0 +1,44 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Antmicro.
+// SPDX-License-Identifier: CC0-1.0
+
+module t (
+   output reg [1020:0] res1,
+   output reg [1020:0] res2,
+   output reg [1022:0] res3,
+   output reg [1022:0] res4
+   );
+   always_inline always_inline(res1, res2);
+   dont_inline dont_inline(res3, res4);
+endmodule
+
+module always_inline(
+   output reg [1020:0] res1,
+   output reg [1020:0] res2
+   );
+
+   wire [1023:0] a;
+   wire [478:0] b;
+
+   assign b = a[510:32];
+   assign res1  = {542'b0, b};
+   assign res2 = {542'b1, b};
+endmodule
+
+// SEL does not have proper offset so we do not have guarantee that it will be
+// emitted as '[' operator, thus we do not exclude it from inlining.
+module dont_inline(
+   output reg [1022:0] res1,
+   output reg [1022:0] res2
+   );
+
+   wire [1023:0] a;
+   wire [480:0] b;
+
+   // LSB % 32 != 0
+   assign b = a[510:30];
+   assign res1  = {542'b0, b};
+   assign res2 = {542'b1, b};
+endmodule

test_regress/t/t_gate_inline_wide_noexclude_small_wide.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('vlt')
+
+test.lint(verilator_flags2=['--stats', '--expand-limit 5'])
+
+test.file_grep(test.stats, r'Optimizations, Gate excluded wide expressions\s+(\d+)', 0)
+
+test.passes()