BytecodeBasicBlock::computeImpl() should not keep iterating blocks if all jump targets have already been found.
https://bugs.webkit.org/show_bug.cgi?id=165820
Reviewed by Saam Barati.
Currently, if an opcode is a branch type opcode, BytecodeBasicBlock::computeImpl()
will iterate over all basic blocks looking for the block containing the jump
target, and it will continue to do this even when all the jump targets have been
found. This is wasted work, and all the more so given that most branch type
opcodes only have a single jump target.
* bytecode/BytecodeBasicBlock.cpp:
(JSC::BytecodeBasicBlock::computeImpl):
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@209820 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Source/JavaScriptCore/bytecode/BytecodeBasicBlock.cpp b/Source/JavaScriptCore/bytecode/BytecodeBasicBlock.cpp
index bb75121..47c481d 100644
--- a/Source/JavaScriptCore/bytecode/BytecodeBasicBlock.cpp
+++ b/Source/JavaScriptCore/bytecode/BytecodeBasicBlock.cpp
@@ -151,11 +151,22 @@
Vector<unsigned, 1> bytecodeOffsetsJumpedTo;
findJumpTargetsForBytecodeOffset(codeBlock, instructionsBegin, bytecodeOffset, bytecodeOffsetsJumpedTo);
+ size_t numberOfJumpTargets = bytecodeOffsetsJumpedTo.size();
+ ASSERT(numberOfJumpTargets);
for (unsigned i = 0; i < basicBlocks.size(); i++) {
BytecodeBasicBlock* otherBlock = basicBlocks[i].get();
- if (bytecodeOffsetsJumpedTo.contains(otherBlock->leaderOffset()))
+ if (bytecodeOffsetsJumpedTo.contains(otherBlock->leaderOffset())) {
linkBlocks(block, otherBlock);
+ --numberOfJumpTargets;
+ if (!numberOfJumpTargets)
+ break;
+ }
}
+ // numberOfJumpTargets may not be 0 here if there are multiple jumps targeting the same
+ // basic blocks (e.g. in a switch type opcode). Since we only decrement numberOfJumpTargets
+ // once per basic block, the duplicates are not accounted for. For our purpose here,
+ // that doesn't matter because we only need to link to the target block once regardless
+ // of how many ways this block can jump there.
if (isUnconditionalBranch(opcodeID))
fallsThrough = false;
