From 5b24282a50654ff86c018387d0624be7147f443d Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Sun, 25 Jul 2021 18:00:52 -0700
Subject: [PATCH] [WebAssembly] Remove dominator dependency in WasmEHPrepare
 (NFC)

Dominator trees were previously used for an optimization related to
`wasm.lsda` but the optimization was removed in D97309. Currently
dominators are not doing anything in this pass. Also removes some
`include` lines without which it compiles.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D106811
---
 lib/CodeGen/WasmEHPrepare.cpp | 23 +++--------------------
 1 file changed, 3 insertions(+), 20 deletions(-)

diff --git a/lib/CodeGen/WasmEHPrepare.cpp b/lib/CodeGen/WasmEHPrepare.cpp
index 19ebbe3a1c8..c4c84cd921f 100644
--- a/lib/CodeGen/WasmEHPrepare.cpp
+++ b/lib/CodeGen/WasmEHPrepare.cpp
@@ -77,20 +77,12 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/Triple.h"
-#include "llvm/Analysis/DomTreeUpdater.h"
-#include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/TargetLowering.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/CodeGen/WasmEHFuncInfo.h"
-#include "llvm/IR/Dominators.h"
 #include "llvm/IR/IRBuilder.h"
-#include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/IntrinsicsWebAssembly.h"
 #include "llvm/InitializePasses.h"
-#include "llvm/Pass.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 
 using namespace llvm;
@@ -124,7 +116,6 @@ public:
   static char ID; // Pass identification, replacement for typeid
 
   WasmEHPrepare() : FunctionPass(ID) {}
-  void getAnalysisUsage(AnalysisUsage &AU) const override;
   bool doInitialization(Module &M) override;
   bool runOnFunction(Function &F) override;
 
@@ -137,16 +128,11 @@ public:
 char WasmEHPrepare::ID = 0;
 INITIALIZE_PASS_BEGIN(WasmEHPrepare, DEBUG_TYPE,
                       "Prepare WebAssembly exceptions", false, false)
-INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 INITIALIZE_PASS_END(WasmEHPrepare, DEBUG_TYPE, "Prepare WebAssembly exceptions",
                     false, false)
 
 FunctionPass *llvm::createWasmEHPass() { return new WasmEHPrepare(); }
 
-void WasmEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
-  AU.addRequired<DominatorTreeWrapperPass>();
-}
-
 bool WasmEHPrepare::doInitialization(Module &M) {
   IRBuilder<> IRB(M.getContext());
   LPadContextTy = StructType::get(IRB.getInt32Ty(),   // lpad_index
@@ -159,14 +145,14 @@ bool WasmEHPrepare::doInitialization(Module &M) {
 // Erase the specified BBs if the BB does not have any remaining predecessors,
 // and also all its dead children.
 template <typename Container>
-static void eraseDeadBBsAndChildren(const Container &BBs, DomTreeUpdater *DTU) {
+static void eraseDeadBBsAndChildren(const Container &BBs) {
   SmallVector<BasicBlock *, 8> WL(BBs.begin(), BBs.end());
   while (!WL.empty()) {
     auto *BB = WL.pop_back_val();
     if (!pred_empty(BB))
       continue;
     WL.append(succ_begin(BB), succ_end(BB));
-    DeleteDeadBlock(BB, DTU);
+    DeleteDeadBlock(BB);
   }
 }
 
@@ -178,9 +164,6 @@ bool WasmEHPrepare::runOnFunction(Function &F) {
 }
 
 bool WasmEHPrepare::prepareThrows(Function &F) {
-  auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
-  DomTreeUpdater DTU(&DT, /*PostDominatorTree*/ nullptr,
-                     DomTreeUpdater::UpdateStrategy::Eager);
   Module &M = *F.getParent();
   IRBuilder<> IRB(F.getContext());
   bool Changed = false;
@@ -203,7 +186,7 @@ bool WasmEHPrepare::prepareThrows(Function &F) {
     InstList.erase(std::next(BasicBlock::iterator(ThrowI)), InstList.end());
     IRB.SetInsertPoint(BB);
     IRB.CreateUnreachable();
-    eraseDeadBBsAndChildren(Succs, &DTU);
+    eraseDeadBBsAndChildren(Succs);
   }
 
   return Changed;