[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

diff --git a/llvm/include/llvm/CodeGen/WasmEHFuncInfo.h b/llvm/include/llvm/CodeGen/WasmEHFuncInfo.h
index aaca8474349ab0dc251607418e3d82e5853fcaa9..887a1467b3e49f439664ed3a01e4a92b66a807a6 100644 (file)
--- a/llvm/include/llvm/CodeGen/WasmEHFuncInfo.h
+++ b/llvm/include/llvm/CodeGen/WasmEHFuncInfo.h
@@ -28,10 +28,6 @@ struct WasmEHFuncInfo {
   // When there is an entry <A, B>, if an exception is not caught by A, it
   // should next unwind to the EH pad B.
   DenseMap<BBOrMBB, BBOrMBB> EHPadUnwindMap;
-  // For entry <A, B>, A is a BB with an instruction that may throw
-  // (invoke/cleanupret in LLVM IR, call/rethrow in the backend) and B is an EH
-  // pad that A unwinds to.
-  DenseMap<BBOrMBB, BBOrMBB> ThrowUnwindMap;
 
   // Helper functions
   const BasicBlock *getEHPadUnwindDest(const BasicBlock *BB) const {
@@ -40,18 +36,9 @@ struct WasmEHFuncInfo {
   void setEHPadUnwindDest(const BasicBlock *BB, const BasicBlock *Dest) {
     EHPadUnwindMap[BB] = Dest;
   }
-  const BasicBlock *getThrowUnwindDest(BasicBlock *BB) const {
-    return ThrowUnwindMap.lookup(BB).get<const BasicBlock *>();
-  }
-  void setThrowUnwindDest(const BasicBlock *BB, const BasicBlock *Dest) {
-    ThrowUnwindMap[BB] = Dest;
-  }
   bool hasEHPadUnwindDest(const BasicBlock *BB) const {
     return EHPadUnwindMap.count(BB);
   }
-  bool hasThrowUnwindDest(const BasicBlock *BB) const {
-    return ThrowUnwindMap.count(BB);
-  }
 
   MachineBasicBlock *getEHPadUnwindDest(MachineBasicBlock *MBB) const {
     return EHPadUnwindMap.lookup(MBB).get<MachineBasicBlock *>();
@@ -59,18 +46,9 @@ struct WasmEHFuncInfo {
   void setEHPadUnwindDest(MachineBasicBlock *MBB, MachineBasicBlock *Dest) {
     EHPadUnwindMap[MBB] = Dest;
   }
-  MachineBasicBlock *getThrowUnwindDest(MachineBasicBlock *MBB) const {
-    return ThrowUnwindMap.lookup(MBB).get<MachineBasicBlock *>();
-  }
-  void setThrowUnwindDest(MachineBasicBlock *MBB, MachineBasicBlock *Dest) {
-    ThrowUnwindMap[MBB] = Dest;
-  }
   bool hasEHPadUnwindDest(MachineBasicBlock *MBB) const {
     return EHPadUnwindMap.count(MBB);
   }
-  bool hasThrowUnwindDest(MachineBasicBlock *MBB) const {
-    return ThrowUnwindMap.count(MBB);
-  }
 };
 
 // Analyze the IR in the given function to build WasmEHFuncInfo.

diff --git a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index de4252aebdf248a27e366a772d2c0db96aff076c..ee2ca90e5d9fc079df8ac11e040b398ee6215839 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -321,13 +321,6 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
       NewMap[MBBMap[Src]] = MBBMap[Dst];
     }
     EHInfo.EHPadUnwindMap = std::move(NewMap);
-    NewMap.clear();
-    for (auto &KV : EHInfo.ThrowUnwindMap) {
-      const auto *Src = KV.first.get<const BasicBlock *>();
-      const auto *Dst = KV.second.get<const BasicBlock *>();
-      NewMap[MBBMap[Src]] = MBBMap[Dst];
-    }
-    EHInfo.ThrowUnwindMap = std::move(NewMap);
   }
 }
 

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index f57b86835d2ddae34c0435f8c258697435833d6c..33921a2c56d95224d4e3b1bcb6c16e6b1840fa11 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1684,6 +1684,8 @@ static void findUnwindDestinations(
 
   if (IsWasmCXX) {
     findWasmUnwindDestinations(FuncInfo, EHPadBB, Prob, UnwindDests);
+    assert(UnwindDests.size() <= 1 &&
+           "There should be at most one unwind destination for wasm");
     return;
   }
 

diff --git a/llvm/lib/CodeGen/WasmEHPrepare.cpp b/llvm/lib/CodeGen/WasmEHPrepare.cpp
index e9986f566c37b98df897be4dd78f3de6c544ab3a..a58da13d9b0b36bf04d2f95ec499b73a4ea48924 100644 (file)
--- 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);
-  }
 }

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
index 65958e00eb3278757393f34b81ec704f59adc0ac..1c4f42cc26d635a6f604993a693b3e55170bb034 100644 (file)
--- a/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
@@ -330,7 +330,7 @@ bool WebAssemblyLateEHPrepare::addExceptionExtraction(MachineFunction &MF) {
     } else {
       BuildMI(ElseMBB, DL, TII.get(WebAssembly::RETHROW));
       if (EHInfo->hasEHPadUnwindDest(EHPad))
-        EHInfo->setThrowUnwindDest(ElseMBB, EHInfo->getEHPadUnwindDest(EHPad));
+        ElseMBB->addSuccessor(EHInfo->getEHPadUnwindDest(EHPad));
     }
   }
 

diff --git a/llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll b/llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
index ed1996f72849631e1c67a4abe186dece7bccf86a..01bac8e63d1a4300a9cfac4a232fb2685dd0a850 100644 (file)
--- a/llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
+++ b/llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
@@ -105,7 +105,7 @@ try.cont:                                         ; preds = %entry, %catch, %cat
 ; CHECK:             i32.call  $drop=, __cxa_begin_catch
 ; CHECK:             try
 ; CHECK:               call      foo
-; CHECK:               br        2                     # 2: down to label10
+; CHECK:               br        2                     # 2: down to label9
 ; CHECK:             catch
 ; CHECK:               call      __cxa_end_catch
 ; CHECK:               rethrow                         # down to catch3
@@ -116,7 +116,7 @@ try.cont:                                         ; preds = %entry, %catch, %cat
 ; CHECK:         catch     {{.*}}                      # catch3:
 ; CHECK:           call      __cxa_end_catch
 ; CHECK:           rethrow                             # to caller
-; CHECK:         end_try                               # label10:
+; CHECK:         end_try                               # label9:
 ; CHECK:         call      __cxa_end_catch
 ; CHECK:         br        2                           # 2: down to label6
 ; CHECK:       end_try