First rivision of PR #6638

docs/guide/exe_verilator.rst

@@ -719,7 +719,7 @@ Summary:
    automatically. Variables explicitly annotated with
    :option:`/*verilator&32;split_var*/` are still split.
 
-.. option:: --fslice-opt-limit
+.. option:: --fslice-element-limit
    Rarely needed.  Set the maximum array size (number of elements) 
    for slice optimization to avoid excessive memory usage.
 

src/V3Options.cpp

@@ -1458,17 +1458,16 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc,
     DECL_OPTION("-freloop", FOnOff, &m_fReloop);
     DECL_OPTION("-freorder", FOnOff, &m_fReorder);
     DECL_OPTION("-fslice", FOnOff, &m_fSlice);
+    DECL_OPTION("-fslice-element-limit", CbVal, [this, fl](const char* valp) {
+        m_fSliceElementLimit = std::atoi(valp);
+        if (m_fSliceElementLimit < 0) fl->v3fatal("--fslice-element-limit must be >= 0: " << valp);
+    });
     DECL_OPTION("-fsplit", FOnOff, &m_fSplit);
     DECL_OPTION("-fsubst", FOnOff, &m_fSubst);
     DECL_OPTION("-fsubst-const", FOnOff, &m_fSubstConst);
     DECL_OPTION("-ftable", FOnOff, &m_fTable);
     DECL_OPTION("-ftaskify-all-forked", FOnOff, &m_fTaskifyAll).undocumented();  // Debug
     DECL_OPTION("-fvar-split", FOnOff, &m_fVarSplit);
-    DECL_OPTION("-fslice-opt-limit", CbVal, [this, fl](const char* valp) {
-        m_fSliceOptLimit = std::atoi(valp);
-        if (m_fSliceOptLimit < 1) fl->v3fatal("--fslice-opt-limit must be >= 1: " << valp);
-    });
-
     DECL_OPTION("-G", CbPartialMatch, [this](const char* optp) { addParameter(optp, false); });
     DECL_OPTION("-gate-stmts", Set, &m_gateStmts);
     DECL_OPTION("-gdb", CbCall, []() {});  // Processed only in bin/verilator shell

src/V3Options.h

@@ -413,13 +413,13 @@ private:
     bool m_fReloop;      // main switch: -fno-reloop: reform loops
     bool m_fReorder;     // main switch: -fno-reorder: reorder assignments in blocks
     bool m_fSlice = true;  // main switch: -fno-slice: array assignment slicing
+    int  m_fSliceElementLimit = 256;  // main switch: --fslice-element-limit
     bool m_fSplit;       // main switch: -fno-split: always assignment splitting
     bool m_fSubst;       // main switch: -fno-subst: substitute expression temp values
     bool m_fSubstConst;  // main switch: -fno-subst-const: final constant substitution
     bool m_fTable;       // main switch: -fno-table: lookup table creation
     bool m_fTaskifyAll = false;  // main switch: --ftaskify-all-forked
     bool m_fVarSplit;    // main switch: -fno-var-split: automatic variable splitting
-    int m_fSliceOptLimit = 256;  // main switch: --fslice-opt-limit
     // clang-format on
 
     bool m_available = false;  // Set to true at the end of option parsing
@@ -727,13 +727,13 @@ public:
     bool fReloop() const { return m_fReloop; }
     bool fReorder() const { return m_fReorder; }
     bool fSlice() const { return m_fSlice; }
+    int  fSliceElementLimit() const { return m_fSliceElementLimit; }
     bool fSplit() const { return m_fSplit; }
     bool fSubst() const { return m_fSubst; }
     bool fSubstConst() const { return m_fSubstConst; }
     bool fTable() const { return m_fTable; }
     bool fTaskifyAll() const { return m_fTaskifyAll; }
     bool fVarSplit() const { return m_fVarSplit; }
-    int fSliceOptLimit() const { return m_fSliceOptLimit; }
 
     std::string traceClassBase() const VL_MT_SAFE;  // Deprecated
     std::string traceClassLang() const VL_MT_SAFE;  // Deprecated

src/V3Slice.cpp

@@ -58,7 +58,7 @@ class SliceVisitor final : public VNVisitor {
 
     // STATE - across all visitors
     VDouble0 m_statAssigns;  // Statistic tracking
-    VDouble0 m_statSliceLimitSkips;  // Statistic tracking
+    VDouble0 m_statSliceElementSkips;  // Statistic tracking
 
     // STATE - for current visit position (use VL_RESTORER)
     AstNode* m_assignp = nullptr;  // Assignment we are under
@@ -251,8 +251,9 @@ class SliceVisitor final : public VNVisitor {
 
         // Skip optimization if array is too large
         const int elements = arrayp->rangep()->elementsConst();
-        if (elements > v3Global.opt.fSliceOptLimit()) {
-            ++m_statSliceLimitSkips;
+        const int elementLimit = v3Global.opt.fSliceElementLimit();
+        if (elements > elementLimit && elementLimit > 0) {
+            ++m_statSliceElementSkips;
             return false;
         }
 
@@ -390,7 +391,7 @@ public:
     explicit SliceVisitor(AstNetlist* nodep) { iterate(nodep); }
     ~SliceVisitor() override {
         V3Stats::addStat("Optimizations, Slice array assignments", m_statAssigns);
-        V3Stats::addStat("Optimizations, Slice array skips due to size limit", m_statSliceLimitSkips);
+        V3Stats::addStat("Optimizations, Slice array skips due to size limit", m_statSliceElementSkips);
     }
 };
 

test_regress/t/t_opt_slice_element_limit.py

@@ -11,9 +11,9 @@ import vltest_bootstrap
 
 test.scenarios('simulator')
 
-test.top_filename = "t/t_opt_slice_limit.v"
+test.top_filename = "t/t_opt_slice_element_limit.v"
 
-test.compile(verilator_flags2=['--stats', '--fslice-opt-limit', '10'])
+test.compile(verilator_flags2=['--stats', '--fslice-element-limit', '10'])
 
 test.file_grep(test.stats, r'Optimizations, Slice array skips due to size limit\s+(\d+)', 4)
 

test_regress/t/t_opt_slice_element_limit_allow_all.py

@@ -0,0 +1,20 @@
+#!/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('simulator')
+
+test.top_filename = "t/t_opt_slice_element_limit.v"
+
+test.compile(verilator_flags2=['--stats', '--fslice-element-limit', '0'])
+
+test.file_grep(test.stats, r'Optimizations, Slice array skips due to size limit\s+(\d+)', 0)
+
+test.passes()

test_regress/t/t_opt_slice_element_limit_bad.py

@@ -11,9 +11,9 @@ import vltest_bootstrap
 
 test.scenarios('simulator')
 
-test.top_filename = "t/t_opt_slice_limit.v"
+test.top_filename = "t/t_opt_slice_element_limit.v"
 
 test.lint(fails=True,
-          verilator_flags2=['--stats', '--fslice-opt-limit', '-100'])
+          verilator_flags2=['--stats', '--fslice-element-limit', '-100'])
 
 test.passes()

test_regress/t/t_opt_slice_element_limit_default.py

@@ -11,7 +11,7 @@ import vltest_bootstrap
 
 test.scenarios('simulator')
 
-test.top_filename = "t/t_opt_slice_limit.v"
+test.top_filename = "t/t_opt_slice_element_limit.v"
 
 test.compile(verilator_flags2=['--stats'])