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authorwolfbeast <mcwerewolf@wolfbeast.com>2019-11-10 11:39:27 +0100
committerwolfbeast <mcwerewolf@wolfbeast.com>2019-11-10 11:39:27 +0100
commit974a481d12bf430891725bd3662876358e57e11a (patch)
treecad011151456251fef2f1b8d02ef4b4e45fad61a /js/src/vm/Scope.h
parent6bd66b1728eeddb058066edda740aaeb2ceaec23 (diff)
parent736d25cbec4541186ed46c935c117ce4d1c7f3bb (diff)
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Merge branch 'master' into js-modules
# Conflicts: # modules/libpref/init/all.js
Diffstat (limited to 'js/src/vm/Scope.h')
-rw-r--r--js/src/vm/Scope.h131
1 files changed, 97 insertions, 34 deletions
diff --git a/js/src/vm/Scope.h b/js/src/vm/Scope.h
index 5304d6713..4a4ae8090 100644
--- a/js/src/vm/Scope.h
+++ b/js/src/vm/Scope.h
@@ -12,6 +12,7 @@
#include "jsobj.h"
#include "jsopcode.h"
+#include "jsutil.h"
#include "gc/Heap.h"
#include "gc/Policy.h"
@@ -111,6 +112,47 @@ class BindingName
void trace(JSTracer* trc);
};
+/**
+ * The various {Global,Module,...}Scope::Data classes consist of always-present
+ * bits, then a trailing array of BindingNames. The various Data classes all
+ * end in a TrailingNamesArray that contains sized/aligned space for *one*
+ * BindingName. Data instances that contain N BindingNames, are then allocated
+ * in sizeof(Data) + (space for (N - 1) BindingNames). Because this class's
+ * |data_| field is properly sized/aligned, the N-BindingName array can start
+ * at |data_|.
+ *
+ * This is concededly a very low-level representation, but we want to only
+ * allocate once for data+bindings both, and this does so approximately as
+ * elegantly as C++ allows.
+ */
+class TrailingNamesArray
+{
+ private:
+ alignas(BindingName) unsigned char data_[sizeof(BindingName)];
+
+ private:
+ // Some versions of GCC treat it as a -Wstrict-aliasing violation (ergo a
+ // -Werror compile error) to reinterpret_cast<> |data_| to |T*|, even
+ // through |void*|. Placing the latter cast in these separate functions
+ // breaks the chain such that affected GCC versions no longer warn/error.
+ void* ptr() {
+ return data_;
+ }
+
+ public:
+ // Explicitly ensure no one accidentally allocates scope data without
+ // poisoning its trailing names.
+ TrailingNamesArray() = delete;
+
+ explicit TrailingNamesArray(size_t nameCount) {
+ if (nameCount)
+ JS_POISON(&data_, 0xCC, sizeof(BindingName) * nameCount);
+ }
+ BindingName* start() { return reinterpret_cast<BindingName*>(ptr()); }
+
+ BindingName& operator[](size_t i) { return start()[i]; }
+};
+
class BindingLocation
{
public:
@@ -337,16 +379,19 @@ class LexicalScope : public Scope
//
// lets - [0, constStart)
// consts - [constStart, length)
- uint32_t constStart;
- uint32_t length;
+ uint32_t constStart = 0;
+ uint32_t length = 0;
// Frame slots [0, nextFrameSlot) are live when this is the innermost
// scope.
- uint32_t nextFrameSlot;
+ uint32_t nextFrameSlot = 0;
// The array of tagged JSAtom* names, allocated beyond the end of the
// struct.
- BindingName names[1];
+ TrailingNamesArray trailingNames;
+
+ explicit Data(size_t nameCount) : trailingNames(nameCount) {}
+ Data() = delete;
void trace(JSTracer* trc);
};
@@ -401,10 +446,11 @@ Scope::is<LexicalScope>() const
}
//
-// Scope corresponding to a function. Holds formal parameter names and, if the
-// function parameters contain no expressions that might possibly be
-// evaluated, the function's var bindings. For example, in these functions,
-// the FunctionScope will store a/b/c bindings but not d/e/f bindings:
+// Scope corresponding to a function. Holds formal parameter names, special
+// internal names (see FunctionScope::isSpecialName), and, if the function
+// parameters contain no expressions that might possibly be evaluated, the
+// function's var bindings. For example, in these functions, the FunctionScope
+// will store a/b/c bindings but not d/e/f bindings:
//
// function f1(a, b) {
// var cÍž
@@ -433,11 +479,11 @@ class FunctionScope : public Scope
// The canonical function of the scope, as during a scope walk we
// often query properties of the JSFunction (e.g., is the function an
// arrow).
- GCPtrFunction canonicalFunction;
+ GCPtrFunction canonicalFunction = {};
// If parameter expressions are present, parameters act like lexical
// bindings.
- bool hasParameterExprs;
+ bool hasParameterExprs = false;
// Bindings are sorted by kind in both frames and environments.
//
@@ -452,17 +498,20 @@ class FunctionScope : public Scope
// positional formals - [0, nonPositionalFormalStart)
// other formals - [nonPositionalParamStart, varStart)
// vars - [varStart, length)
- uint16_t nonPositionalFormalStart;
- uint16_t varStart;
- uint32_t length;
+ uint16_t nonPositionalFormalStart = 0;
+ uint16_t varStart = 0;
+ uint32_t length = 0;
// Frame slots [0, nextFrameSlot) are live when this is the innermost
// scope.
- uint32_t nextFrameSlot;
+ uint32_t nextFrameSlot = 0;
// The array of tagged JSAtom* names, allocated beyond the end of the
// struct.
- BindingName names[1];
+ TrailingNamesArray trailingNames;
+
+ explicit Data(size_t nameCount) : trailingNames(nameCount) {}
+ Data() = delete;
void trace(JSTracer* trc);
};
@@ -514,6 +563,8 @@ class FunctionScope : public Scope
return data().nonPositionalFormalStart;
}
+ static bool isSpecialName(ExclusiveContext* cx, JSAtom* name);
+
static Shape* getEmptyEnvironmentShape(ExclusiveContext* cx, bool hasParameterExprs);
};
@@ -548,15 +599,18 @@ class VarScope : public Scope
struct Data
{
// All bindings are vars.
- uint32_t length;
+ uint32_t length = 0;
// Frame slots [firstFrameSlot(), nextFrameSlot) are live when this is
// the innermost scope.
- uint32_t nextFrameSlot;
+ uint32_t nextFrameSlot = 0;
// The array of tagged JSAtom* names, allocated beyond the end of the
// struct.
- BindingName names[1];
+ TrailingNamesArray trailingNames;
+
+ explicit Data(size_t nameCount) : trailingNames(nameCount) {}
+ Data() = delete;
void trace(JSTracer* trc);
};
@@ -638,14 +692,17 @@ class GlobalScope : public Scope
// vars - [varStart, letStart)
// lets - [letStart, constStart)
// consts - [constStart, length)
- uint32_t varStart;
- uint32_t letStart;
- uint32_t constStart;
- uint32_t length;
+ uint32_t varStart = 0;
+ uint32_t letStart = 0;
+ uint32_t constStart = 0;
+ uint32_t length = 0;
// The array of tagged JSAtom* names, allocated beyond the end of the
// struct.
- BindingName names[1];
+ TrailingNamesArray trailingNames;
+
+ explicit Data(size_t nameCount) : trailingNames(nameCount) {}
+ Data() = delete;
void trace(JSTracer* trc);
};
@@ -736,16 +793,19 @@ class EvalScope : public Scope
//
// top-level funcs - [0, varStart)
// vars - [varStart, length)
- uint32_t varStart;
- uint32_t length;
+ uint32_t varStart = 0;
+ uint32_t length = 0;
// Frame slots [0, nextFrameSlot) are live when this is the innermost
// scope.
- uint32_t nextFrameSlot;
+ uint32_t nextFrameSlot = 0;
// The array of tagged JSAtom* names, allocated beyond the end of the
// struct.
- BindingName names[1];
+ TrailingNamesArray trailingNames;
+
+ explicit Data(size_t nameCount) : trailingNames(nameCount) {}
+ Data() = delete;
void trace(JSTracer* trc);
};
@@ -827,7 +887,7 @@ class ModuleScope : public Scope
struct Data
{
// The module of the scope.
- GCPtr<ModuleObject*> module;
+ GCPtr<ModuleObject*> module = {};
// Bindings are sorted by kind.
//
@@ -835,18 +895,21 @@ class ModuleScope : public Scope
// vars - [varStart, letStart)
// lets - [letStart, constStart)
// consts - [constStart, length)
- uint32_t varStart;
- uint32_t letStart;
- uint32_t constStart;
- uint32_t length;
+ uint32_t varStart = 0;
+ uint32_t letStart = 0;
+ uint32_t constStart = 0;
+ uint32_t length = 0;
// Frame slots [0, nextFrameSlot) are live when this is the innermost
// scope.
- uint32_t nextFrameSlot;
+ uint32_t nextFrameSlot = 0;
// The array of tagged JSAtom* names, allocated beyond the end of the
// struct.
- BindingName names[1];
+ TrailingNamesArray trailingNames;
+
+ explicit Data(size_t nameCount) : trailingNames(nameCount) {}
+ Data() = delete;
void trace(JSTracer* trc);
};