Fix --spill-pointers

src/abi/stack.h

@@ -38,9 +38,6 @@ inline Index stackAlign(Index size) {
 // Allocate some space on the stack, and assign it to a local.
 // The local will have the same constant value in all the function, so you can
 // just local.get it anywhere there.
-//
-// FIXME: This function assumes that the stack grows upward, per the convention
-// used by fastcomp. The stack grows downward when using the WASM backend.
 
 inline void
 getStackSpace(Index local, Function* func, Index size, Module& wasm) {
@@ -55,22 +52,25 @@ getStackSpace(Index local, Function* func, Index size, Module& wasm) {
  // TODO: find existing stack usage, and add on top of that - carefully
  Builder builder(wasm);
  auto* block = builder.makeBlock();
- block->list.push_back(builder.makeLocalSet(
- local, builder.makeGlobalGet(stackPointer->name, pointerType)));
  // TODO: add stack max check
  Expression* added;
  if (pointerType == Type::i32) {
  // The stack goes downward in the LLVM wasm backend.
- added = builder.makeBinary(SubInt32,
- builder.makeLocalGet(local, pointerType),
- builder.makeConst(int32_t(size)));
+ added =
+ builder.makeBinary(SubInt32,
+ builder.makeGlobalGet(stackPointer->name, pointerType),
+ builder.makeConst(int32_t(size)));
  } else {
  WASM_UNREACHABLE("unhandled pointerType");
  }
- block->list.push_back(builder.makeGlobalSet(stackPointer->name, added));
+ block->list.push_back(builder.makeGlobalSet(
+ stackPointer->name, builder.makeLocalTee(local, added, pointerType)));
  auto makeStackRestore = [&]() {
- return builder.makeGlobalSet(stackPointer->name,
- builder.makeLocalGet(local, pointerType));
+ return builder.makeGlobalSet(
+ stackPointer->name,
+ builder.makeBinary(AddInt32,
+ builder.makeLocalGet(local, pointerType),
+ builder.makeConst(int32_t(size))));
  };
  // add stack restores to the returns
  FindAllPointers<Return> finder(func->body);