Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 257 insertions, 0 deletions

diff --git a/js/src/jit/BytecodeAnalysis.cpp b/js/src/jit/BytecodeAnalysis.cpp
new file mode 100644
index 0000000000..ed60296fec
--- /dev/null
+++ b/js/src/jit/BytecodeAnalysis.cpp
@@ -0,0 +1,257 @@
+/* -*- 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/. */
+
+#include "jit/BytecodeAnalysis.h"
+
+#include "jit/JitSpewer.h"
+#include "jit/WarpBuilder.h"
+#include "vm/BytecodeIterator.h"
+#include "vm/BytecodeLocation.h"
+#include "vm/BytecodeUtil.h"
+
+#include "vm/BytecodeIterator-inl.h"
+#include "vm/BytecodeLocation-inl.h"
+#include "vm/JSScript-inl.h"
+
+using namespace js;
+using namespace js::jit;
+
+BytecodeAnalysis::BytecodeAnalysis(TempAllocator& alloc, JSScript* script)
+    : script_(script), infos_(alloc) {}
+
+bool BytecodeAnalysis::init(TempAllocator& alloc) {
+  if (!infos_.growByUninitialized(script_->length())) {
+    return false;
+  }
+
+  // Clear all BytecodeInfo.
+  mozilla::PodZero(infos_.begin(), infos_.length());
+  infos_[0].init(/*stackDepth=*/0);
+
+  // WarpBuilder can compile try blocks, but doesn't support handling
+  // exceptions. If exception unwinding would resume in a catch or finally
+  // block, we instead bail out to the baseline interpreter. Finally blocks can
+  // still be reached by normal means, but the catch block is unreachable and is
+  // not compiled. We therefore need some special machinery to prevent OSR into
+  // Warp code in the following cases:
+  //
+  // (1) Loops in catch blocks:
+  //
+  //       try {
+  //         ..
+  //       } catch (e) {
+  //         while (..) {} // Can't OSR here.
+  //       }
+  //
+  // (2) Loops only reachable via a catch block:
+  //
+  //       for (;;) {
+  //         try {
+  //           throw 3;
+  //         } catch (e) {
+  //           break;
+  //         }
+  //       }
+  //       while (..) {} // Loop is only reachable via the catch-block.
+  //
+  // To deal with both of these cases, we track whether the current op is
+  // 'normally reachable' (reachable without exception handling).
+  // Forward jumps propagate this flag to their jump targets (see
+  // BytecodeInfo::jumpTargetNormallyReachable) and when the analysis reaches a
+  // jump target it updates its normallyReachable flag based on the target's
+  // flag.
+  //
+  // Inlining a function without a normally reachable return can cause similar
+  // problems. To avoid this, we mark such functions as uninlineable.
+  bool normallyReachable = true;
+  bool normallyReachableReturn = false;
+
+  for (const BytecodeLocation& it : AllBytecodesIterable(script_)) {
+    JSOp op = it.getOp();
+    uint32_t offset = it.bytecodeToOffset(script_);
+
+    JitSpew(JitSpew_BaselineOp, "Analyzing op @ %u (end=%u): %s",
+            unsigned(offset), unsigned(script_->length()), CodeName(op));
+
+    checkWarpSupport(op);
+
+    // If this bytecode info has not yet been initialized, it's not reachable.
+    if (!infos_[offset].initialized) {
+      continue;
+    }
+
+    uint32_t stackDepth = infos_[offset].stackDepth;
+
+    if (infos_[offset].jumpTarget) {
+      normallyReachable = infos_[offset].jumpTargetNormallyReachable;
+    }
+
+#ifdef DEBUG
+    size_t endOffset = offset + it.length();
+    for (size_t checkOffset = offset + 1; checkOffset < endOffset;
+         checkOffset++) {
+      MOZ_ASSERT(!infos_[checkOffset].initialized);
+    }
+#endif
+    uint32_t nuses = it.useCount();
+    uint32_t ndefs = it.defCount();
+
+    MOZ_ASSERT(stackDepth >= nuses);
+    stackDepth -= nuses;
+    stackDepth += ndefs;
+
+    // If stack depth exceeds max allowed by analysis, fail fast.
+    MOZ_ASSERT(stackDepth <= BytecodeInfo::MAX_STACK_DEPTH);
+
+    switch (op) {
+      case JSOp::TableSwitch: {
+        uint32_t defaultOffset = it.getTableSwitchDefaultOffset(script_);
+        int32_t low = it.getTableSwitchLow();
+        int32_t high = it.getTableSwitchHigh();
+
+        infos_[defaultOffset].init(stackDepth);
+        infos_[defaultOffset].setJumpTarget(normallyReachable);
+
+        uint32_t ncases = high - low + 1;
+
+        for (uint32_t i = 0; i < ncases; i++) {
+          uint32_t targetOffset = it.tableSwitchCaseOffset(script_, i);
+          if (targetOffset != defaultOffset) {
+            infos_[targetOffset].init(stackDepth);
+            infos_[targetOffset].setJumpTarget(normallyReachable);
+          }
+        }
+        break;
+      }
+
+      case JSOp::Try: {
+        for (const TryNote& tn : script_->trynotes()) {
+          if (tn.start == offset + JSOpLength_Try &&
+              (tn.kind() == TryNoteKind::Catch ||
+               tn.kind() == TryNoteKind::Finally)) {
+            uint32_t catchOrFinallyOffset = tn.start + tn.length;
+            uint32_t targetDepth =
+                tn.kind() == TryNoteKind::Finally ? stackDepth + 2 : stackDepth;
+            BytecodeInfo& targetInfo = infos_[catchOrFinallyOffset];
+            targetInfo.init(targetDepth);
+            targetInfo.setJumpTarget(/* normallyReachable = */ false);
+          }
+        }
+        break;
+      }
+
+      case JSOp::LoopHead:
+        infos_[offset].loopHeadCanOsr = normallyReachable;
+        break;
+
+#ifdef DEBUG
+      case JSOp::Exception:
+        // Sanity check: ops only emitted in catch blocks are never
+        // normally reachable.
+        MOZ_ASSERT(!normallyReachable);
+        break;
+#endif
+
+      case JSOp::Return:
+      case JSOp::RetRval:
+        if (normallyReachable) {
+          normallyReachableReturn = true;
+        }
+        break;
+
+      default:
+        break;
+    }
+
+    bool jump = it.isJump();
+    if (jump) {
+      // Case instructions do not push the lvalue back when branching.
+      uint32_t newStackDepth = stackDepth;
+      if (it.is(JSOp::Case)) {
+        newStackDepth--;
+      }
+
+      uint32_t targetOffset = it.getJumpTargetOffset(script_);
+
+#ifdef DEBUG
+      // If this is a backedge, the target JSOp::LoopHead must have been
+      // analyzed already. Furthermore, if the backedge is normally reachable,
+      // the loop head must be normally reachable too (loopHeadCanOsr can be
+      // used to check this since it's equivalent).
+      if (targetOffset < offset) {
+        MOZ_ASSERT(infos_[targetOffset].initialized);
+        MOZ_ASSERT_IF(normallyReachable, infos_[targetOffset].loopHeadCanOsr);
+      }
+#endif
+
+      infos_[targetOffset].init(newStackDepth);
+      infos_[targetOffset].setJumpTarget(normallyReachable);
+    }
+
+    // Handle any fallthrough from this opcode.
+    if (it.fallsThrough()) {
+      BytecodeLocation fallthroughLoc = it.next();
+      MOZ_ASSERT(fallthroughLoc.isInBounds(script_));
+      uint32_t fallthroughOffset = fallthroughLoc.bytecodeToOffset(script_);
+
+      infos_[fallthroughOffset].init(stackDepth);
+
+      // Treat the fallthrough of a branch instruction as a jump target.
+      if (jump) {
+        infos_[fallthroughOffset].setJumpTarget(normallyReachable);
+      }
+    }
+  }
+
+  // Flag (reachable) resume offset instructions.
+  for (uint32_t offset : script_->resumeOffsets()) {
+    BytecodeInfo& info = infos_[offset];
+    if (info.initialized) {
+      info.hasResumeOffset = true;
+    }
+  }
+
+  if (!normallyReachableReturn) {
+    script_->setUninlineable();
+  }
+
+  return true;
+}
+
+void BytecodeAnalysis::checkWarpSupport(JSOp op) {
+  switch (op) {
+#define DEF_CASE(OP) case JSOp::OP:
+    WARP_UNSUPPORTED_OPCODE_LIST(DEF_CASE)
+#undef DEF_CASE
+    if (script_->canIonCompile()) {
+      JitSpew(JitSpew_IonAbort, "Disabling Warp support for %s:%d:%d due to %s",
+              script_->filename(), script_->lineno(), script_->column(),
+              CodeName(op));
+      script_->disableIon();
+    }
+    break;
+    default:
+      break;
+  }
+}
+
+bool js::jit::ScriptUsesEnvironmentChain(JSScript* script) {
+  if (script->isModule() || script->initialEnvironmentShape() ||
+      (script->function() &&
+       script->function()->needsSomeEnvironmentObject())) {
+    return true;
+  }
+
+  AllBytecodesIterable iterator(script);
+
+  for (const BytecodeLocation& location : iterator) {
+    if (OpUsesEnvironmentChain(location.getOp())) {
+      return true;
+    }
+  }
+
+  return false;
+}