Code folding (#1076)

Adds a pass that folds code, i.e. merges it when possible. See details in comment in the pass implementation cpp.

This is enabled by default in -Os and -Oz. Seems risky to enable anywhere else, as it does add branches - likely predictable ones so maybe no slowdown, but still some risk.

Code size numbers:

wasm-backend: 196331
+ binaryen -Os (before): 182598
+ binaryen -Os (with folding): 181943

asm2wasm -Os (before): 172463
asm2wasm -Os (with folding): 168774

So this reduces wasm-backend output by an additional 0.5% than it could before. Mainly this is because the wasm backend already has code folding, whereas on asm2wasm output, where we didn't have folding before, this saves over 2%. The 0.5% improvement on the wasm backend's output might be because this can fold more types of code than LLVM can (it can fold nested control flow, in particular).

1 files changed, 0 insertions, 23 deletions

diff --git a/src/pass.h b/src/pass.h
index 198d5dcb5..21836ebf9 100644
--- a/src/pass.h
+++ b/src/pass.h
@@ -237,29 +237,6 @@ public:
 // but registering them here in addition allows them to communicate
 // e.g. through PassRunner::getLast
 
-// Handles names in a module, in particular adding names without duplicates
-class NameManager : public WalkerPass<PostWalker<NameManager>> {
- public:
-  Name getUnique(std::string prefix);
-  // TODO: getUniqueInFunction
-
-  // visitors
-  void visitBlock(Block* curr);
-  void visitLoop(Loop* curr);
-  void visitBreak(Break* curr);
-  void visitSwitch(Switch* curr);
-  void visitCall(Call* curr);
-  void visitCallImport(CallImport* curr);
-  void visitFunctionType(FunctionType* curr);
-  void visitFunction(Function* curr);
-  void visitImport(Import* curr);
-  void visitExport(Export* curr);
-
-private:
-  std::set<Name> names;
-  size_t counter = 0;
-};
-
 // Prints out a module
 class Printer : public Pass {
 protected: