Make mstatus.SD/FS/VS dependent on parameters (#190)

* Make mstatus.SD/FS/VS dependent on parameters

---------

Signed-off-by: Derek Hower <[email protected]>

Author: dhower-qc

.vscode/settings.json

@@ -9,5 +9,5 @@
   "files.watcherExclude": {
     "**/.home": true
   },
-  "asciidoc.antora.enableAntoraSupport": true
+  "asciidoc.antora.showEnableAntoraPrompt": true
 }

arch/csr/mstatus.yaml

@@ -22,9 +22,29 @@ mstatus:
         
         Read-only bit that summarizes whether either the FS, XS, or VS
         fields signal the presence of some dirty state.
-      type: RO-H
-      reset_value: UNDEFINED_LEGAL
-      affectedBy: [F, D, V]
+      definedBy:
+        anyOf: [F,V] # NOTE: if you implement a custom extension overlay that writes to XS, then you need to add your extension here in the overlay as well
+      type(): |
+        # this is read-only if FS and VS are both read-only
+        # otherwise, it is read-only with hardware update
+
+        if (implemented?(ExtensionName::F) && (HW_MSTATUS_FS_DIRTY_UPDATE != "never")) {
+          return CsrFieldType::ROH;
+        } else if (implemented?(ExtensionName::V) && (HW_MSTATUS_VS_DIRTY_UPDATE != "never")) {
+          return CsrFieldType::ROH;
+        } else {
+          return CsrFieldType::RO;
+        }
+      reset_value(): |
+        # the reset value is known if both FS and VS are legal
+        # make this a function call so that it can be displayed succinctly in docs
+
+        if (mstatus_sd_has_known_reset()) {
+          return mstatus_sd_reset_value();
+        } else {
+          return UNDEFINED_LEGAL;
+        }
+
     MPV:
       location: 39
       base: 64
@@ -339,7 +359,8 @@ mstatus:
           # there will be no hardware update in this case because we know the F extension isn't implemented
           return MSTATUS_FS_WRITEABLE ? CsrFieldType::RW : CsrFieldType::RO;
         }
-      definedBy: F
+      definedBy:
+        anyOf: [F, S]
       reset_value(): |
         if (CSR[misa].F == 1'b1){
           return UNDEFINED_LEGAL;
@@ -410,9 +431,38 @@ mstatus:
         When a vector register or vector CSR is written, VS obtains the value 3.
         Values 1 and 2 are valid write values for software, but are not interpreted by hardware
         other than to possibly enable a previously-disabled vector unit.
-      type: RW-H
-      reset_value: UNDEFINED_LEGAL
-      definedBy: V
+      definedBy:
+        anyOf: [V, S]
+      type(): |
+        if (CSR[misa].V == 1'b1){
+          return CsrFieldType::RWH;
+        } else if ((CSR[misa].S == 1'b0) && (CSR[misa].V == 1'b0)) {
+          # must be read-only-0
+          return CsrFieldType::RO;
+        } else {
+          # there will be no hardware update in this case because we know the V extension isn't implemented
+          return MSTATUS_VS_WRITEABLE ? CsrFieldType::RW : CsrFieldType::RO;
+        }
+      reset_value(): |
+        if (CSR[misa].V == 1'b1){
+          return UNDEFINED_LEGAL;
+        } else if ((CSR[misa].S == 1'b0) && (CSR[misa].V == 1'b0)) {
+          # must be read-only-0
+          return 0;
+        } else {
+          # there will be no hardware update in this case because we know the V extension isn't implemented
+          return MSTATUS_VS_WRITEABLE ? UNDEFINED_LEGAL : 0;
+        }
+      sw_write(csr_value): |
+        if (CSR[misa].V == 1'b1){
+          return ary_includes?<$array_size(MSTATUS_VS_LEGAL_VALUES), 2>(MSTATUS_VS_LEGAL_VALUES, csr_value.FS) ? csr_value.FS : UNDEFINED_LEGAL_DETERMINISTIC;
+        } else if ((CSR[misa].S == 1'b0) && (CSR[misa].V == 1'b0)) {
+          # must be read-only-0
+          return 0;
+        } else {
+          # there will be no hardware update in this case because we know the V extension isn't implemented
+          return ary_includes?<$array_size(MSTATUS_VS_LEGAL_VALUES), 2>(MSTATUS_VS_LEGAL_VALUES, csr_value.FS) ? csr_value.FS : UNDEFINED_LEGAL_DETERMINISTIC;
+        }
     SPP:
       location: 8
       description: |

arch/ext/F.yaml

@@ -246,13 +246,13 @@ F:
         Values are:
         [separator="!"]
         !===
-        h! none  ! Hardware never writes `mstatus.FS`
+        h! never  ! Hardware never writes `mstatus.FS`
         h! precise  ! Hardware writes `mstatus.FS` to the Dirty (3) state precisely when F registers are modified
         h! imprecise ! Hardware writes `mstatus.FS` imprecisely. This will result in a call to unpredictable() on any attempt to read `mstatus` or write FP state.
         !===
       schema:
         type: string
-        enum: ["none", "precise", "imprecise"]
+        enum: ["never", "precise", "imprecise"]
     MSTATUS_FS_LEGAL_VALUES:
       description: |
         The set of values that mstatus.FS will accept from a software write.
@@ -268,4 +268,4 @@ F:
         assert MSTATUS_FS_LEGAL_VALUES.include?(0) && MSTATUS_FS_LEGAL_VALUES.include?(3) if ext?(:F)
 
         # if HW is writing FS, then Dirty (3) better be a supported value
-        assert MSTATUS_FS_LEGAL_VALUES.include?(3) if ext?(:F) && (HW_MSTATUS_FS_DIRTY_UPDATE != "none")
+        assert MSTATUS_FS_LEGAL_VALUES.include?(3) if ext?(:F) && (HW_MSTATUS_FS_DIRTY_UPDATE != "never")

arch/ext/S.yaml

@@ -254,6 +254,15 @@ S:
         type: boolean
       extra_validation:
         assert MSTATUS_FS_WRITEABLE == true if ext?(:F)
+    MSTATUS_VS_WRITEABLE:
+      description: |
+        When `S` is enabled but `V` is not, mstatus.VS is optionally writeable.
+
+        This parameter only has an effect when both S and V mode are disabled.
+      schema:
+        type: boolean
+      extra_validation:
+        assert MSTATUS_VS_WRITEABLE == true if ext?(:V)
     MSTATUS_FS_LEGAL_VALUES:
       description: |
         The set of values that mstatus.FS will accept from a software write.
@@ -267,6 +276,22 @@ S:
       also_defined_in: F
       extra_validation: |
         assert MSTATUS_FS_LEGAL_VALUES.include?(0) && MSTATUS_FS_LEGAL_VALUES.include?(3) if ext?(:F)
+    MSTATUS_VS_LEGAL_VALUES:
+      description: |
+        The set of values that mstatus.VS will accept from a software write.
+      schema:
+        type: array
+        items:
+          type: integer
+          enum: [0,1,2,3]
+        maxItems: 4
+        uniqueItems: true
+      also_defined_in: V
+      extra_validation: |
+        assert MSTATUS_VS_LEGAL_VALUES.include?(0) && MSTATUS_VS_LEGAL_VALUES.include?(3) if ext?(:V)
+
+        # if HW is writing VS, then Dirty (3) better be a supported value
+        assert MSTATUS_VS_LEGAL_VALUES.include?(3) if ext?(:V) && (HW_MSTATUS_VS_DIRTY_UPDATE != "never")
     MSTATUS_TVM_IMPLEMENTED:
       description: |
         Whether or not mstatus.TVM is implemented.

arch/ext/V.yaml

@@ -14,4 +14,34 @@ V:
       description: |
         Indicates whether or not the `V` extension can be disabled with the `misa.V` bit.
       schema:
-        type: boolean
+        type: boolean
+    HW_MSTATUS_VS_DIRTY_UPDATE:
+      description: |
+        Indicates whether or not hardware will write to `mstatus.VS`
+
+        Values are:
+        [separator="!"]
+        !===
+        h! never  ! Hardware never writes `mstatus.VS`
+        h! precise  ! Hardware writes `mstatus.VS` to the Dirty (3) state precisely when V registers are modified
+        h! imprecise ! Hardware writes `mstatus.VS` imprecisely. This will result in a call to unpredictable() on any attempt to read `mstatus` or write vector state.
+        !===
+      schema:
+        type: string
+        enum: ["never", "precise", "imprecise"]
+    MSTATUS_VS_LEGAL_VALUES:
+      description: |
+        The set of values that mstatus.VS will accept from a software write.
+      schema:
+        type: array
+        items:
+          type: integer
+          enum: [0,1,2,3]
+        maxItems: 4
+        uniqueItems: true
+      also_defined_in: S
+      extra_validation: |
+        assert MSTATUS_VS_LEGAL_VALUES.include?(0) && MSTATUS_VS_LEGAL_VALUES.include?(3) if ext?(:V)
+
+        # if HW is writing VS, then Dirty (3) better be a supported value
+        assert MSTATUS_VS_LEGAL_VALUES.include?(3) if ext?(:V) && (HW_MSTATUS_VS_DIRTY_UPDATE != "never")

arch/isa/globals.isa

@@ -2798,3 +2798,45 @@ function write_memory {
   }
 }
 
+function mstatus_sd_has_known_reset
+{
+  returns Boolean
+  description {
+    Returns true if the mstatus.SD bit has a defined reset value, as determined by various parameters.
+  }
+  body {
+    # the reset value is known if both FS and VS are known
+
+    Boolean fs_has_single_value =
+      ((!implemented?(ExtensionName::F)) || ($array_size(MSTATUS_FS_LEGAL_VALUES) == 1));
+
+    Boolean vs_has_single_value =
+      ((!implemented?(ExtensionName::V)) || ($array_size(MSTATUS_VS_LEGAL_VALUES) == 1));
+
+    return fs_has_single_value && vs_has_single_value;
+  }
+}
+
+function mstatus_sd_reset_value
+{
+  returns Bits<1>
+  description {
+    Returns the reset value of mstatus.SD when known
+  }
+  body {
+    # the reset value is known if both FS and VS are known
+    assert(mstatus_sd_has_known_reset(),
+           "mstatus_sd_reset_value is only defined when mstatus_sd_has_known_reset() == true");
+
+    Bits<2> fs_value, vs_value; # defaults to 0
+
+    if ((!implemented?(ExtensionName::F)) || ($array_size(MSTATUS_FS_LEGAL_VALUES) == 1)) {
+      fs_value = (!implemented?(ExtensionName::F)) ? 0 : MSTATUS_FS_LEGAL_VALUES[0];
+    }
+    if ((!implemented?(ExtensionName::V)) || ($array_size(MSTATUS_VS_LEGAL_VALUES) == 1)) {
+      fs_value = (!implemented?(ExtensionName::V)) ? 0 : MSTATUS_VS_LEGAL_VALUES[0];
+    }
+
+    return ((fs_value == 3) || (vs_value == 3)) ? 1 : 0;
+  }
+}

cfgs/generic_rv64/params.yaml

@@ -514,4 +514,7 @@ params:
   MSTATUS_FS_WRITEABLE: true
   MSTATUS_TVM_IMPLEMENTED: true
   HW_MSTATUS_FS_DIRTY_UPDATE: precise
+  MSTATUS_VS_WRITEABLE: true
+  MSTATUS_VS_LEGAL_VALUES: [0,1,2,3]
+  HW_MSTATUS_VS_DIRTY_UPDATE: precise
   FORCE_UPGRADE_CBO_INVAL_TO_FLUSH: true

lib/idl/ast.rb

@@ -361,6 +361,8 @@ def print_ast(indent = 0, indent_size: 2, io: $stdout)
 
     # @!macro freeze_tree
     def freeze_tree(global_symtab)
+      return if frozen?
+
       @children.each { |child| child.freeze_tree(global_symtab) }
       freeze
     end
@@ -1095,6 +1097,8 @@ def initialize(input, interval, user_type)
     end
 
     def freeze_tree(global_symtab)
+      return if frozen?
+
       # call type to get it set before we freeze the object
       type(global_symtab)
       freeze
@@ -1257,6 +1261,8 @@ def initialize(input, interval, name, size, fields)
 
     # @!macro freeze_tree
     def freeze_tree(global_symtab)
+      return if frozen?
+
       type(global_symtab)
       freeze
     end
@@ -1498,7 +1504,9 @@ def type_check(symtab)
       if var.type(symtab).kind == :array
         value_result = value_try do
           index_value = index.value(symtab)
-          type_error "Array index out of range" if index_value >= var.type(symtab).width
+          if var.type(symtab).width != :unknown
+            type_error "Array index out of range" if index_value >= var.type(symtab).width
+          end
         end # Ok, doesn't need to be known
 
       elsif var.type(symtab).integral?
@@ -2161,22 +2169,26 @@ def to_ast
   class MultiVariableDeclarationAst < AstNode
     include Declaration
 
+    # @return [AstNode] Declared type
     def type_name = @children[0]
-    def var_names = @children[1..]
+
+    # @return [Array<AstNode>] Variable names
+    def var_name_nodes = @children[1..]
 
     def initialize(input, interval, type_name, var_names)
       super(input, interval, [type_name] + var_names)
 
       @global = false
     end
 
+    # mark this declaration as being in global scope
     def make_global
       @global = true
     end
 
     # @return [Array<String>] Variables being declared
     def var_names
-      var_names.map(&:text_value)
+      var_name_nodes.map(&:text_value)
     end
 
     # @!macro type_check
@@ -2186,6 +2198,7 @@ def type_check(symtab)
       add_symbol(symtab)
     end
 
+    # @!macro type
     def type(symtab)
       if @global
         type_name.type(symtab).clone.make_global
@@ -2196,13 +2209,13 @@ def type(symtab)
 
     # @!macro add_symbol
     def add_symbol(symtab)
-      var_names.each do |vname|
-        symtab.add(vname.text_values, Var.new(vname.text_value, type(symtab), type(symtab).default))
+      var_name_nodes.each do |vname|
+        symtab.add(vname.text_value, Var.new(vname.text_value, type(symtab), type(symtab).default))
       end
     end
 
     # @!macro to_idl
-    def to_idl = "#{type_name.to_idl} #{var_names.map(&:to_idl).join(', ')}"
+    def to_idl = "#{type_name.to_idl} #{var_name_nodes.map(&:to_idl).join(', ')}"
   end
 
   class VariableDeclarationSyntaxNode < Treetop::Runtime::SyntaxNode
@@ -3415,6 +3428,8 @@ def initialize(input, interval, class_name, member_name)
 
     # @!macro freeze_tree
     def freeze_tree(global_symtab)
+      return if frozen?
+
       enum_def_ast = global_symtab.archdef.global_ast.enums.find { |e| e.name == @enum_class_name }
 
       @enum_def_type =
@@ -4179,6 +4194,8 @@ def type_check(symtab)
     end
 
     def freeze_tree(symtab)
+      return if frozen?
+
       if @type_name == "Bits"
         # precalculate size if possible
         begin
@@ -4849,6 +4866,8 @@ def initialize(input, interval, name, targs, return_types, arguments, desc, body
 
     # @!macro freeze_tree
     def freeze_tree(global_symtab)
+      return if frozen?
+
       unless templated?
         arguments(global_symtab)
       end
@@ -5679,6 +5698,8 @@ def initialize(input, interval, idx, field_name)
     end
 
     def freeze_tree(symtab)
+      return if frozen?
+
       value_result = value_try do
         @value = calc_value(symtab)
       end
@@ -5819,6 +5840,8 @@ def initialize(input, interval, idx)
     end
 
     def freeze_tree(symtab)
+      return if frozen?
+
       @archdef = symtab.archdef # remember archdef, used by gen_adoc pass
       @idx.freeze_tree(symtab)
       freeze

lib/idl/passes/gen_adoc.rb

@@ -159,6 +159,12 @@ def gen_adoc(indent = 0, indent_spaces: 2)
     end
   end
 
+  class MultiVariableDeclarationAst
+    def gen_adoc(indent = 0, indent_spaces: 2)
+      "#{' ' * indent}#{type_name.gen_adoc(0, indent_spaces:)} #{var_name_nodes.map { |var| var.gen_adoc(0, indent_spaces:) }.join(', ')}"
+    end
+  end
+
   class TernaryOperatorExpressionAst
     def gen_adoc(indent = 0, indent_spaces: 2)
       "#{' ' * indent}#{condition.gen_adoc(0, indent_spaces:)} ? #{true_expression.gen_adoc(0, indent_spaces:)} : #{false_expression.gen_adoc(0, indent_spaces:)}"