diff options
Diffstat (limited to 'src/passes/RemoveUnusedBrs.cpp')
| -rw-r--r-- | src/passes/RemoveUnusedBrs.cpp | 44 |
1 files changed, 28 insertions, 16 deletions
diff --git a/src/passes/RemoveUnusedBrs.cpp b/src/passes/RemoveUnusedBrs.cpp index cb3ff69ee..614503581 100644 --- a/src/passes/RemoveUnusedBrs.cpp +++ b/src/passes/RemoveUnusedBrs.cpp @@ -106,10 +106,11 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> { } else if (auto* block = curr->dynCast<Block>()) { // any breaks flowing to here are unnecessary, as we get here anyhow auto name = block->name; + auto& list = block->list; if (name.is()) { - size_t size = flows.size(); - size_t skip = 0; - for (size_t i = 0; i < size; i++) { + Index size = flows.size(); + Index skip = 0; + for (Index i = 0; i < size; i++) { auto* flow = (*flows[i])->dynCast<Break>(); if (flow && flow->name == name) { if (!flow->value) { @@ -129,11 +130,22 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> { flows.resize(size - skip); } // drop a nop at the end of a block, which prevents a value flowing - while (block->list.size() > 0 && block->list.back()->is<Nop>()) { - block->list.resize(block->list.size() - 1); + while (list.size() > 0 && list.back()->is<Nop>()) { + list.resize(list.size() - 1); self->anotherCycle = true; } } + // A value flowing is only valid if it is a value that the block actually + // flows out. If it is never reached, it does not flow out, and may be + // invalid to represent as such. + auto size = list.size(); + for (Index i = 0; i < size; i++) { + if (i != size - 1 && list[i]->type == unreachable) { + // No value flows out of this block. + self->stopValueFlow(); + break; + } + } } else if (curr->is<Nop>()) { // ignore (could be result of a previous cycle) self->stopValueFlow(); @@ -280,7 +292,7 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> { } } // TODO: if-else can be turned into a br_if as well, if one of the sides is a dead end - // we handle the case of a returned value to a set_local later down, see + // we handle the case of a returned value to a local.set later down, see // visitSetLocal. } @@ -515,7 +527,7 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> { super::doWalkFunction(func); assert(ifStack.empty()); // flows may contain returns, which are flowing out and so can be optimized - for (size_t i = 0; i < flows.size(); i++) { + for (Index i = 0; i < flows.size(); i++) { auto* flow = (*flows[i])->dynCast<Return>(); if (!flow) continue; if (!flow->value) { @@ -835,7 +847,7 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> { } // If one arm is a br, we prefer a br_if and the set later: - // (set_local $x + // (local.set $x // (if (result i32) // (..condition..) // (br $somewhere) @@ -846,7 +858,7 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> { // (br_if $somewhere // (..condition..) // ) - // (set_local $x + // (local.set $x // (..result) // ) // TODO: handle a condition in the br? need to watch for side effects @@ -888,38 +900,38 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> { // we can remove. If this is not a tee, then we remove the get // as well as the if-else opcode in the binary format, which is // great: - // (set_local $x + // (local.set $x // (if (result i32) // (..condition..) // (..result) - // (get_local $x) + // (local.get $x) // ) // ) // => // (if // (..condition..) - // (set_local $x + // (local.set $x // (..result) // ) // ) // If this is a tee, then we can do the same operation but // inside a block, and keep the get: - // (tee_local $x + // (local.tee $x // (if (result i32) // (..condition..) // (..result) - // (get_local $x) + // (local.get $x) // ) // ) // => // (block (result i32) // (if // (..condition..) - // (set_local $x + // (local.set $x // (..result) // ) // ) - // (get_local $x) + // (local.get $x) // ) // We save the if-else opcode, and add the block's opcodes. // This may be detrimental, however, often the block can be |