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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef vm_BytecodeUtil_inl_h
+#define vm_BytecodeUtil_inl_h
+
+#include "vm/BytecodeUtil.h"
+
+#include "frontend/SourceNotes.h" // SrcNote, SrcNoteType, SrcNoteIterator
+#include "vm/JSScript.h"
+
+namespace js {
+
+static inline unsigned GetDefCount(jsbytecode* pc) {
+ /*
+ * Add an extra pushed value for Or/And opcodes, so that they are included
+ * in the pushed array of stack values for type inference.
+ */
+ JSOp op = JSOp(*pc);
+ switch (op) {
+ case JSOp::Or:
+ case JSOp::And:
+ case JSOp::Coalesce:
+ return 1;
+ case JSOp::Pick:
+ case JSOp::Unpick:
+ /*
+ * Pick pops and pushes how deep it looks in the stack + 1
+ * items. i.e. if the stack were |a b[2] c[1] d[0]|, pick 2
+ * would pop b, c, and d to rearrange the stack to |a c[0]
+ * d[1] b[2]|.
+ */
+ return pc[1] + 1;
+ default:
+ return StackDefs(op);
+ }
+}
+
+static inline unsigned GetUseCount(jsbytecode* pc) {
+ JSOp op = JSOp(*pc);
+ if (op == JSOp::Pick || op == JSOp::Unpick) {
+ return pc[1] + 1;
+ }
+
+ return StackUses(op, pc);
+}
+
+static inline JSOp ReverseCompareOp(JSOp op) {
+ switch (op) {
+ case JSOp::Gt:
+ return JSOp::Lt;
+ case JSOp::Ge:
+ return JSOp::Le;
+ case JSOp::Lt:
+ return JSOp::Gt;
+ case JSOp::Le:
+ return JSOp::Ge;
+ case JSOp::Eq:
+ case JSOp::Ne:
+ case JSOp::StrictEq:
+ case JSOp::StrictNe:
+ return op;
+ default:
+ MOZ_CRASH("unrecognized op");
+ }
+}
+
+static inline JSOp NegateCompareOp(JSOp op) {
+ switch (op) {
+ case JSOp::Gt:
+ return JSOp::Le;
+ case JSOp::Ge:
+ return JSOp::Lt;
+ case JSOp::Lt:
+ return JSOp::Ge;
+ case JSOp::Le:
+ return JSOp::Gt;
+ case JSOp::Eq:
+ return JSOp::Ne;
+ case JSOp::Ne:
+ return JSOp::Eq;
+ case JSOp::StrictNe:
+ return JSOp::StrictEq;
+ case JSOp::StrictEq:
+ return JSOp::StrictNe;
+ default:
+ MOZ_CRASH("unrecognized op");
+ }
+}
+
+class BytecodeRange {
+ public:
+ BytecodeRange(JSContext* cx, JSScript* script)
+ : script(cx, script), pc(script->code()), end(pc + script->length()) {}
+ bool empty() const { return pc == end; }
+ jsbytecode* frontPC() const { return pc; }
+ JSOp frontOpcode() const { return JSOp(*pc); }
+ size_t frontOffset() const { return script->pcToOffset(pc); }
+ void popFront() { pc += GetBytecodeLength(pc); }
+
+ private:
+ RootedScript script;
+ jsbytecode* pc;
+ jsbytecode* end;
+};
+
+class BytecodeRangeWithPosition : private BytecodeRange {
+ public:
+ using BytecodeRange::empty;
+ using BytecodeRange::frontOffset;
+ using BytecodeRange::frontOpcode;
+ using BytecodeRange::frontPC;
+
+ BytecodeRangeWithPosition(JSContext* cx, JSScript* script)
+ : BytecodeRange(cx, script),
+ initialLine(script->lineno()),
+ lineno(script->lineno()),
+ column(script->column()),
+ sn(script->notes()),
+ snpc(script->code()),
+ isEntryPoint(false),
+ isBreakpoint(false),
+ seenStepSeparator(false),
+ wasArtifactEntryPoint(false) {
+ if (!sn->isTerminator()) {
+ snpc += sn->delta();
+ }
+ updatePosition();
+ while (frontPC() != script->main()) {
+ popFront();
+ }
+
+ if (frontOpcode() != JSOp::JumpTarget) {
+ isEntryPoint = true;
+ } else {
+ wasArtifactEntryPoint = true;
+ }
+ }
+
+ void popFront() {
+ BytecodeRange::popFront();
+ if (empty()) {
+ isEntryPoint = false;
+ } else {
+ updatePosition();
+ }
+
+ // The following conditions are handling artifacts introduced by the
+ // bytecode emitter, such that we do not add breakpoints on empty
+ // statements of the source code of the user.
+ if (wasArtifactEntryPoint) {
+ wasArtifactEntryPoint = false;
+ isEntryPoint = true;
+ }
+
+ if (isEntryPoint && frontOpcode() == JSOp::JumpTarget) {
+ wasArtifactEntryPoint = isEntryPoint;
+ isEntryPoint = false;
+ }
+ }
+
+ size_t frontLineNumber() const { return lineno; }
+ size_t frontColumnNumber() const { return column; }
+
+ // Entry points are restricted to bytecode offsets that have an
+ // explicit mention in the line table. This restriction avoids a
+ // number of failing cases caused by some instructions not having
+ // sensible (to the user) line numbers, and it is one way to
+ // implement the idea that the bytecode emitter should tell the
+ // debugger exactly which offsets represent "interesting" (to the
+ // user) places to stop.
+ bool frontIsEntryPoint() const { return isEntryPoint; }
+
+ // Breakable points are explicitly marked by the emitter as locations where
+ // the debugger may want to allow users to pause.
+ bool frontIsBreakablePoint() const { return isBreakpoint; }
+
+ // Breakable step points are the first breakable point after a
+ // SrcNote::StepSep note has been encountered.
+ bool frontIsBreakableStepPoint() const {
+ return isBreakpoint && seenStepSeparator;
+ }
+
+ private:
+ void updatePosition() {
+ if (isBreakpoint) {
+ isBreakpoint = false;
+ seenStepSeparator = false;
+ }
+
+ // Determine the current line number by reading all source notes up to
+ // and including the current offset.
+ jsbytecode* lastLinePC = nullptr;
+ SrcNoteIterator iter(sn);
+ for (; !iter.atEnd() && snpc <= frontPC();
+ ++iter, snpc += (*iter)->delta()) {
+ auto sn = *iter;
+
+ SrcNoteType type = sn->type();
+ if (type == SrcNoteType::ColSpan) {
+ ptrdiff_t colspan = SrcNote::ColSpan::getSpan(sn);
+ MOZ_ASSERT(ptrdiff_t(column) + colspan >= 0);
+ column += colspan;
+ lastLinePC = snpc;
+ } else if (type == SrcNoteType::SetLine) {
+ lineno = SrcNote::SetLine::getLine(sn, initialLine);
+ column = 0;
+ lastLinePC = snpc;
+ } else if (type == SrcNoteType::NewLine) {
+ lineno++;
+ column = 0;
+ lastLinePC = snpc;
+ } else if (type == SrcNoteType::Breakpoint) {
+ isBreakpoint = true;
+ lastLinePC = snpc;
+ } else if (type == SrcNoteType::StepSep) {
+ seenStepSeparator = true;
+ lastLinePC = snpc;
+ }
+ }
+
+ sn = *iter;
+ isEntryPoint = lastLinePC == frontPC();
+ }
+
+ size_t initialLine;
+ size_t lineno;
+ size_t column;
+ const SrcNote* sn;
+ jsbytecode* snpc;
+ bool isEntryPoint;
+ bool isBreakpoint;
+ bool seenStepSeparator;
+ bool wasArtifactEntryPoint;
+};
+
+} // namespace js
+
+#endif /* vm_BytecodeUtil_inl_h */
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