Fix concat of long hashed names in traces etc (#2854)

docs/CONTRIBUTORS

@@ -23,6 +23,7 @@ Garrett Smith
 Geza Lore
 Gianfranco Costamagna
 Glen Gibb
+Graham Rushton
 Harald Heckmann
 Howard Su
 Huang Rui

src/V3String.cpp

@@ -380,12 +380,52 @@ void VHashSha256::selfTest() {
 // VName
 
 string VName::dehash(const string& in) {
-    const string::size_type pos = in.find("__Vhsh");
+    static const char VHSH[] = "__Vhsh";
-    if (VL_LIKELY(pos == string::npos)) return in;
+    static const size_t DOT_LEN = strlen("__DOT__");
-    const string vhsh = in.substr(pos);
+    std::string dehashed;
-    const auto& it = s_dehashMap.find(vhsh);
+
-    UASSERT(it != s_dehashMap.end(), "String not in reverse hash map '" << vhsh << "'");
+    // Need to split 'in' into components separated by __DOT__, 'last_dot_pos'
-    return in.substr(0, pos) + it->second;
+    // keeps track of the position after the most recently found instance of __DOT__
+    for (string::size_type last_dot_pos = 0; last_dot_pos < in.size(); ) {
+        const string::size_type next_dot_pos = in.find("__DOT__", last_dot_pos);
+        // Two iterators defining the range between the last and next dots.
+        auto search_begin = std::begin(in) + last_dot_pos;
+        auto search_end = next_dot_pos == string::npos ? std::end(in)
+                                                       : std::begin(in) + next_dot_pos;
+
+        // Search for __Vhsh between the two dots.
+        auto begin_vhsh = std::search(search_begin, search_end,
+                                      std::begin(VHSH), std::end(VHSH) - 1);
+        if (begin_vhsh != search_end) {
+            std::string vhsh(begin_vhsh, search_end);
+            const auto& it = s_dehashMap.find(vhsh);
+            UASSERT(it != s_dehashMap.end(), "String not in reverse hash map '" << vhsh << "'");
+            // Is this not the first component, but the first to require dehashing?
+            if (last_dot_pos > 0 && dehashed.empty()) {
+                // Seed 'dehashed' with the previously processed components.
+                dehashed = in.substr(0, last_dot_pos);
+            }
+            // Append the unhashed part of the component.
+            dehashed += std::string(search_begin, begin_vhsh);
+            // Append the bit that was lost to truncation but retrieved from the dehash map.
+            dehashed += it->second;
+        }
+        // This component doesn't need dehashing but a previous one might have.
+        else if (!dehashed.empty()) {
+            dehashed += std::string(search_begin, search_end);
+        }
+
+        if (next_dot_pos != string::npos) {
+            // Is there a __DOT__ to add to the dehashed version of 'in'?
+            if (!dehashed.empty()) {
+                dehashed += "__DOT__";
+            }
+            last_dot_pos = next_dot_pos + DOT_LEN;
+        } else {
+            last_dot_pos = string::npos;
+        }
+    }
+    return dehashed.empty() ? in : dehashed;
 }
 
 string VName::hashedName() {

test_regress/t/t_trace_complex.out

@@ -39,6 +39,9 @@ $timescale   1ps $end
    $var wire  2 % v_strp [1:0] $end
    $var wire  4 & v_strp_strp [3:0] $end
    $var wire  2 ' v_unip_strp [1:0] $end
+   $scope module a_module_instantiation_with_a_very_long_name_that_once_its_signals_get_concatenated_and_inlined_will_almost_certainly_result_in_them_getting_hashed $end
+    $var wire 32 J PARAM [31:0] $end
+   $upscope $end
    $scope module p2 $end
     $var wire 32 H PARAM [31:0] $end
    $upscope $end
@@ -92,6 +95,7 @@ b00000000 F
 0G
 b00000000000000000000000000000010 H
 b00000000000000000000000000000011 I
+b00000000000000000000000000000100 J
 #10
 b00000000000000000000000000000001 $
 b11 %

test_regress/t/t_trace_complex.v

@@ -78,6 +78,8 @@ module t (clk);
    p #(.PARAM(2)) p2 ();
    p #(.PARAM(3)) p3 ();
 
+   p #(.PARAM(4)) a_module_instantiation_with_a_very_long_name_that_once_its_signals_get_concatenated_and_inlined_will_almost_certainly_result_in_them_getting_hashed ();
+
    always @ (posedge clk) begin
       cyc <= cyc + 1;
       v_strp <= ~v_strp;

test_regress/t/t_trace_complex_fst.out

@@ -58,15 +58,19 @@ $upscope $end
 $scope module p3 $end
 $var parameter 32 B PARAM $end
 $upscope $end
+$scope module a_module_instantiation_with_a_very_long_name_that_once_its_signals_get_concatenated_and_inlined_will_almost_certainly_result_in_them_getting_hashed $end
+$var parameter 32 C PARAM $end
+$upscope $end
 $upscope $end
 $scope module $unit $end
-$var bit 1 C global_bit $end
+$var bit 1 D global_bit $end
 $upscope $end
 $upscope $end
 $enddefinitions $end
-#0
 $dumpvars
-1C
+#0
+1D
+b00000000000000000000000000000100 C
 b00000000000000000000000000000011 B
 b00000000000000000000000000000010 A
 b00000000000000000000000000000000 @
@@ -101,7 +105,6 @@ b0000 $
 b00 #
 b00000000000000000000000000000000 "
 0!
-$end
 #10
 1!
 b00000000000000000000000000000001 "

test_regress/t/t_trace_complex_fst_sc.out

@@ -1,5 +1,5 @@
 $date
-	Thu Apr  1 15:12:03 2021
+	Mon Apr 19 17:05:53 2021
 
 $end
 $version
@@ -57,15 +57,19 @@ $upscope $end
 $scope module p3 $end
 $var parameter 32 B PARAM $end
 $upscope $end
+$scope module a_module_instantiation_with_a_very_long_name_that_once_its_signals_get_concatenated_and_inlined_will_almost_certainly_result_in_them_getting_hashed $end
+$var parameter 32 C PARAM $end
+$upscope $end
 $upscope $end
 $scope module $unit $end
-$var bit 1 C global_bit $end
+$var bit 1 D global_bit $end
 $upscope $end
 $upscope $end
 $enddefinitions $end
-#0
 $dumpvars
-1C
+#0
+1D
+b00000000000000000000000000000100 C
 b00000000000000000000000000000011 B
 b00000000000000000000000000000010 A
 b00000000000000000000000000000000 @
@@ -100,7 +104,6 @@ b0000 $
 b00 #
 b00000000000000000000000000000000 "
 0!
-$end
 #10
 1!
 b00000000000000000000000000000001 "

test_regress/t/t_trace_complex_params.out

@@ -39,6 +39,9 @@ $timescale   1ps $end
    $var wire  2 % v_strp [1:0] $end
    $var wire  4 & v_strp_strp [3:0] $end
    $var wire  2 ' v_unip_strp [1:0] $end
+   $scope module a_module_instantiation_with_a_very_long_name_that_once_its_signals_get_concatenated_and_inlined_will_almost_certainly_result_in_them_getting_hashed $end
+    $var wire 32 J PARAM [31:0] $end
+   $upscope $end
    $scope module p2 $end
     $var wire 32 H PARAM [31:0] $end
    $upscope $end
@@ -92,6 +95,7 @@ b00000000 F
 0G
 b00000000000000000000000000000010 H
 b00000000000000000000000000000011 I
+b00000000000000000000000000000100 J
 #10
 b00000000000000000000000000000001 $
 b11 %

test_regress/t/t_trace_complex_params_fst.out

@@ -58,15 +58,19 @@ $upscope $end
 $scope module p3 $end
 $var parameter 32 B PARAM $end
 $upscope $end
+$scope module a_module_instantiation_with_a_very_long_name_that_once_its_signals_get_concatenated_and_inlined_will_almost_certainly_result_in_them_getting_hashed $end
+$var parameter 32 C PARAM $end
+$upscope $end
 $upscope $end
 $scope module $unit $end
-$var bit 1 C global_bit $end
+$var bit 1 D global_bit $end
 $upscope $end
 $upscope $end
 $enddefinitions $end
-#0
 $dumpvars
-1C
+#0
+1D
+b00000000000000000000000000000100 C
 b00000000000000000000000000000011 B
 b00000000000000000000000000000010 A
 b00000000000000000000000000000000 @
@@ -101,7 +105,6 @@ b0000 $
 b00 #
 b00000000000000000000000000000000 "
 0!
-$end
 #10
 1!
 b00000000000000000000000000000001 "

test_regress/t/t_trace_complex_params_fst_sc.out

@@ -1,5 +1,5 @@
 $date
-	Thu Apr  1 15:17:39 2021
+	Mon Apr 19 17:07:10 2021
 
 $end
 $version
@@ -57,15 +57,19 @@ $upscope $end
 $scope module p3 $end
 $var parameter 32 B PARAM $end
 $upscope $end
+$scope module a_module_instantiation_with_a_very_long_name_that_once_its_signals_get_concatenated_and_inlined_will_almost_certainly_result_in_them_getting_hashed $end
+$var parameter 32 C PARAM $end
+$upscope $end
 $upscope $end
 $scope module $unit $end
-$var bit 1 C global_bit $end
+$var bit 1 D global_bit $end
 $upscope $end
 $upscope $end
 $enddefinitions $end
-#0
 $dumpvars
-1C
+#0
+1D
+b00000000000000000000000000000100 C
 b00000000000000000000000000000011 B
 b00000000000000000000000000000010 A
 b00000000000000000000000000000000 @
@@ -100,7 +104,6 @@ b0000 $
 b00 #
 b00000000000000000000000000000000 "
 0!
-$end
 #10
 1!
 b00000000000000000000000000000001 "