Merge pull request #1247 from diffblue/past5-fix

`$past` now supports array and struct types

Author: tautschnig

regression/verilog/system-functions/past5.desc

@@ -1,9 +1,8 @@
-KNOWNBUG
+CORE
 past5.sv
 
-^EXIT=0$
+^EXIT=10$
 ^SIGNAL=0$
 --
 ^warning: ignoring
 --
-$past doesn't support the array.

regression/verilog/system-functions/past5.sv

@@ -2,6 +2,6 @@ module main;
 
   logic [31:0] mem[123];
 
-  assert property (##1 mem == $past(mem));
+  assert property (mem == $past(mem));
 
 endmodule

regression/verilog/system-functions/past6.desc

@@ -0,0 +1,8 @@
+CORE
+past6.sv
+
+^EXIT=10$
+^SIGNAL=0$
+--
+^warning: ignoring
+--

regression/verilog/system-functions/past6.sv

@@ -0,0 +1,17 @@
+module main;
+
+  typedef struct {
+    bit some_bit;
+  } inner_struct;
+
+  typedef struct {
+    bit [31:0] array [123];
+    bit other_bit;
+    inner_struct inner;
+  } my_struct;
+
+  my_struct s;
+
+  assert property (s == $past(s));
+
+endmodule

src/verilog/verilog_expr.cpp

@@ -15,6 +15,7 @@ Author: Daniel Kroening, [email protected]
 #include <util/mathematical_types.h>
 #include <util/prefix.h>
 
+#include "verilog_initializer.h"
 #include "verilog_typecheck_base.h"
 #include "verilog_types.h"
 
@@ -535,9 +536,7 @@ exprt verilog_inside_exprt::lower() const
 
 exprt verilog_past_exprt::default_value() const
 {
-  auto zero = from_integer(0, type());
-  if(zero.is_nil())
-    throw "failed to create $past default value";
-  else
-    return std::move(zero);
+  auto value_opt = verilog_default_initializer(type());
+  CHECK_RETURN(value_opt.has_value());
+  return *value_opt;
 }