[WebAssembly] Delete ThrowUnwindDest map from WasmEHFuncInfo

Summary:
Before when we implemented the first EH proposal, 'catch <tag>'
instruction may not catch an exception so there were multiple EH pads an
exception can unwind to. That means a BB could have multiple EH pad
successors.

Now after we switched to the new proposal, every 'catch' instruction
catches an exception, and there is only one catchpad per catchswitch, so
we at most have one EH pad successor, making `ThrowUnwindDest` map in
`WasmEHInfo` unnecessary.

Keeping `ThrowUnwindDest` map in `WasmEHInfo` has its own problems,
because other optimization passes can split a BB that contains possibly
throwing calls (previously invokes), and we have to update the map every
time that happens, which is not easy for common CodeGen passes.

This also correctly updates successor info in LateEHPrepare when we add
a rethrow instruction.

Reviewers: dschuff

Subscribers: sbc100, jgravelle-google, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58486

llvm-svn: 355296

1 files changed, 0 insertions, 18 deletions

diff --git a/llvm/lib/CodeGen/WasmEHPrepare.cpp b/llvm/lib/CodeGen/WasmEHPrepare.cpp
index e9986f5..a58da13 100644
--- a/llvm/lib/CodeGen/WasmEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WasmEHPrepare.cpp
@@ -376,22 +376,4 @@ void llvm::calculateWasmEHInfo(const Function *F, WasmEHFuncInfo &EHInfo) {
         EHInfo.setEHPadUnwindDest(&BB, UnwindBB);
     }
   }
-
-  // Record the unwind destination for invoke and cleanupret instructions.
-  for (const auto &BB : *F) {
-    const Instruction *TI = BB.getTerminator();
-    BasicBlock *UnwindBB = nullptr;
-    if (const auto *Invoke = dyn_cast<InvokeInst>(TI))
-      UnwindBB = Invoke->getUnwindDest();
-    else if (const auto *CleanupRet = dyn_cast<CleanupReturnInst>(TI))
-      UnwindBB = CleanupRet->getUnwindDest();
-    if (!UnwindBB)
-      continue;
-    const Instruction *UnwindPad = UnwindBB->getFirstNonPHI();
-    if (const auto *CatchSwitch = dyn_cast<CatchSwitchInst>(UnwindPad))
-      // Currently there should be only one handler per a catchswitch.
-      EHInfo.setThrowUnwindDest(&BB, *CatchSwitch->handlers().begin());
-    else // cleanuppad
-      EHInfo.setThrowUnwindDest(&BB, UnwindBB);
-  }
 }