Changeset 220047 in webkit for trunk/Source/JavaScriptCore/offlineasm/ast.rb

Timestamp:

Jul 29, 2017, 8:01:12 PM (8 years ago)

Author:

[email protected]

Message:

LLInt offsets extractor should be able to handle C++ constexprs
​https://bugs.webkit.org/show_bug.cgi?id=174964

Reviewed by Saam Barati.

This patch adds new syntax to the offline asm language. The new keyword,
constexpr, takes the subsequent identifier and maps it to a C++ constexpr
expression. Additionally, if the value is not an identifier you can wrap it in
parentheses. e.g. constexpr (myConstexprFunction() + OBJECT_OFFSET(Foo, bar)),
which will get converted into:
static_cast<int64_t>(myConstexprFunction() + OBJECT_OFFSET(Foo, bar));

This patch also changes the data format the LLIntOffsetsExtractor
binary produces. Previously, it would produce unsigned values,
after this patch every value is an int64_t. Using an int64_t is
useful because it means that we can represent any constant needed.
int32_t masks are sign extended then passed then converted to a
negative literal sting in the assembler so it will be the constant
expected.

• llint/LLIntOffsetsExtractor.cpp:

(JSC::LLIntOffsetsExtractor::dummy):

• llint/LowLevelInterpreter.asm:
• llint/LowLevelInterpreter64.asm:
• offlineasm/asm.rb:
• offlineasm/ast.rb:
• offlineasm/generate_offset_extractor.rb:
• offlineasm/offsets.rb:
• offlineasm/parser.rb:
• offlineasm/transform.rb:

File:

• trunk/Source/JavaScriptCore/offlineasm/ast.rb (modified) (2 diffs)

trunk/Source/JavaScriptCore/offlineasm/ast.rb

@@ -946 +946 @@
 end
 
+class ConstExpr < NoChildren
+    attr_reader :variable, :value
+
+    def initialize(codeOrigin, value)
+        super(codeOrigin)
+        @value = value
+    end
+
+    @@mapping = {}
+
+    def self.forName(codeOrigin, text)
+        unless @@mapping[text]
+            @@mapping[text] = ConstExpr.new(codeOrigin, text)
+        end
+        @@mapping[text]
+    end
+
+    def dump
+        "constexpr (#{@value.dump})"
+    end
+
+    def <=>(other)
+        @value <=> other.value
+    end
+
+    def immediate?
+        true
+    end
+end
+
 class ConstDecl < Node
     attr_reader :variable, :value
-    
+
     def initialize(codeOrigin, variable, value)
         super(codeOrigin)
@@ -954 +984 @@
         @value = value
     end
-    
+
     def children
         [@variable, @value]
     end
-    
+
     def mapChildren
         ConstDecl.new(codeOrigin, (yield @variable), (yield @value))
     end
-    
+
     def dump
         "const #{@variable.dump} = #{@value.dump}"