SmallVector (#1912)

Trying to refactor the code to be simpler and less redundant, I ran into some perf issues that it seems like a small vector, with fixed-size storage and optional additional storage as needed, might help with. This implements that class and uses it in a few places.

This seems to help, I see some 1-2% fewer instructions and cycles in `perf stat`, but it's hard to tell if it really makes a noticeable difference.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/ir/ExpressionAnalyzer.cpp b/src/ir/ExpressionAnalyzer.cpp
index e2345d303..28c59491a 100644
--- a/src/ir/ExpressionAnalyzer.cpp
+++ b/src/ir/ExpressionAnalyzer.cpp
@@ -24,7 +24,7 @@ namespace wasm {
 // Given a stack of expressions, checks if the topmost is used as a result.
 // For example, if the parent is a block and the node is before the last position,
 // it is not used.
-bool ExpressionAnalyzer::isResultUsed(std::vector<Expression*> stack, Function* func) {
+bool ExpressionAnalyzer::isResultUsed(ExpressionStack& stack, Function* func) {
   for (int i = int(stack.size()) - 2; i >= 0; i--) {
     auto* curr = stack[i];
     auto* above = stack[i + 1];
@@ -52,7 +52,7 @@ bool ExpressionAnalyzer::isResultUsed(std::vector<Expression*> stack, Function*
 }
 
 // Checks if a value is dropped.
-bool ExpressionAnalyzer::isResultDropped(std::vector<Expression*> stack) {
+bool ExpressionAnalyzer::isResultDropped(ExpressionStack& stack) {
   for (int i = int(stack.size()) - 2; i >= 0; i--) {
     auto* curr = stack[i];
     auto* above = stack[i + 1];