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-rw-r--r--llvm/lib/CodeGen/WasmEHPrepare.cpp171
1 files changed, 46 insertions, 125 deletions
diff --git a/llvm/lib/CodeGen/WasmEHPrepare.cpp b/llvm/lib/CodeGen/WasmEHPrepare.cpp
index 53424556682d..c4c84cd921fa 100644
--- a/llvm/lib/CodeGen/WasmEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WasmEHPrepare.cpp
@@ -77,21 +77,12 @@
//
//===----------------------------------------------------------------------===//
-#include "llvm/ADT/BreadthFirstIterator.h"
-#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;
@@ -117,19 +108,14 @@ class WasmEHPrepare : public FunctionPass {
FunctionCallee CallPersonalityF =
nullptr; // _Unwind_CallPersonality() wrapper
- bool prepareEHPads(Function &F);
bool prepareThrows(Function &F);
-
- bool IsEHPadFunctionsSetUp = false;
- void setupEHPadFunctions(Function &F);
- void prepareEHPad(BasicBlock *BB, bool NeedPersonality, bool NeedLSDA = false,
- unsigned Index = 0);
+ bool prepareEHPads(Function &F);
+ void prepareEHPad(BasicBlock *BB, bool NeedPersonality, unsigned Index = 0);
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;
@@ -142,16 +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
@@ -164,19 +145,18 @@ 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);
}
}
bool WasmEHPrepare::runOnFunction(Function &F) {
- IsEHPadFunctionsSetUp = false;
bool Changed = false;
Changed |= prepareThrows(F);
Changed |= prepareEHPads(F);
@@ -184,9 +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;
@@ -209,102 +186,30 @@ 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;
}
bool WasmEHPrepare::prepareEHPads(Function &F) {
- auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
- bool Changed = false;
+ Module &M = *F.getParent();
+ IRBuilder<> IRB(F.getContext());
- // There are two things to decide: whether we need a personality function call
- // and whether we need a `wasm.lsda()` call and its store.
- //
- // For the personality function call, catchpads with `catch (...)` and
- // cleanuppads don't need it, because exceptions are always caught. Others all
- // need it.
- //
- // For `wasm.lsda()` and its store, in order to minimize the number of them,
- // we need a way to figure out whether we have encountered `wasm.lsda()` call
- // in any of EH pads that dominates the current EH pad. To figure that out, we
- // now visit EH pads in BFS order in the dominator tree so that we visit
- // parent BBs first before visiting its child BBs in the domtree.
- //
- // We keep a set named `ExecutedLSDA`, which basically means "Do we have
- // `wasm.lsda() either in the current EH pad or any of its parent EH pads in
- // the dominator tree?". This is to prevent scanning the domtree up to the
- // root every time we examine an EH pad, in the worst case: each EH pad only
- // needs to check its immediate parent EH pad.
- //
- // - If any of its parent EH pads in the domtree has `wasm.lsda`, this means
- // we don't need `wasm.lsda()` in the current EH pad. We also insert the
- // current EH pad in `ExecutedLSDA` set.
- // - If none of its parent EH pad has `wasm.lsda()`,
- // - If the current EH pad is a `catch (...)` or a cleanuppad, done.
- // - If the current EH pad is neither a `catch (...)` nor a cleanuppad,
- // add `wasm.lsda()` and the store in the current EH pad, and add the
- // current EH pad to `ExecutedLSDA` set.
- //
- // TODO Can we not store LSDA address in user function but make libcxxabi
- // compute it?
- DenseSet<Value *> ExecutedLSDA;
- unsigned Index = 0;
- for (auto DomNode : breadth_first(&DT)) {
- auto *BB = DomNode->getBlock();
- auto *Pad = BB->getFirstNonPHI();
- if (!Pad || (!isa<CatchPadInst>(Pad) && !isa<CleanupPadInst>(Pad)))
+ SmallVector<BasicBlock *, 16> CatchPads;
+ SmallVector<BasicBlock *, 16> CleanupPads;
+ for (BasicBlock &BB : F) {
+ if (!BB.isEHPad())
continue;
- Changed = true;
-
- Value *ParentPad = nullptr;
- if (CatchPadInst *CPI = dyn_cast<CatchPadInst>(Pad)) {
- ParentPad = CPI->getCatchSwitch()->getParentPad();
- if (ExecutedLSDA.count(ParentPad)) {
- ExecutedLSDA.insert(CPI);
- // We insert its associated catchswitch too, because
- // FuncletPadInst::getParentPad() returns a CatchSwitchInst if the child
- // FuncletPadInst is a CleanupPadInst.
- ExecutedLSDA.insert(CPI->getCatchSwitch());
- }
- } else { // CleanupPadInst
- ParentPad = cast<CleanupPadInst>(Pad)->getParentPad();
- if (ExecutedLSDA.count(ParentPad))
- ExecutedLSDA.insert(Pad);
- }
-
- if (CatchPadInst *CPI = dyn_cast<CatchPadInst>(Pad)) {
- if (CPI->getNumArgOperands() == 1 &&
- cast<Constant>(CPI->getArgOperand(0))->isNullValue())
- // In case of a single catch (...), we need neither personality call nor
- // wasm.lsda() call
- prepareEHPad(BB, false);
- else {
- if (ExecutedLSDA.count(CPI))
- // catch (type), but one of parents already has wasm.lsda() call
- prepareEHPad(BB, true, false, Index++);
- else {
- // catch (type), and none of parents has wasm.lsda() call. We have to
- // add the call in this EH pad, and record this EH pad in
- // ExecutedLSDA.
- ExecutedLSDA.insert(CPI);
- ExecutedLSDA.insert(CPI->getCatchSwitch());
- prepareEHPad(BB, true, true, Index++);
- }
- }
- } else if (isa<CleanupPadInst>(Pad)) {
- // Cleanup pads need neither personality call nor wasm.lsda() call
- prepareEHPad(BB, false);
- }
+ auto *Pad = BB.getFirstNonPHI();
+ if (isa<CatchPadInst>(Pad))
+ CatchPads.push_back(&BB);
+ else if (isa<CleanupPadInst>(Pad))
+ CleanupPads.push_back(&BB);
}
+ if (CatchPads.empty() && CleanupPads.empty())
+ return false;
- return Changed;
-}
-
-void WasmEHPrepare::setupEHPadFunctions(Function &F) {
- Module &M = *F.getParent();
- IRBuilder<> IRB(F.getContext());
assert(F.hasPersonalityFn() && "Personality function not found");
// __wasm_lpad_context global variable
@@ -336,16 +241,30 @@ void WasmEHPrepare::setupEHPadFunctions(Function &F) {
"_Unwind_CallPersonality", IRB.getInt32Ty(), IRB.getInt8PtrTy());
if (Function *F = dyn_cast<Function>(CallPersonalityF.getCallee()))
F->setDoesNotThrow();
+
+ unsigned Index = 0;
+ for (auto *BB : CatchPads) {
+ auto *CPI = cast<CatchPadInst>(BB->getFirstNonPHI());
+ // In case of a single catch (...), we don't need to emit a personalify
+ // function call
+ if (CPI->getNumArgOperands() == 1 &&
+ cast<Constant>(CPI->getArgOperand(0))->isNullValue())
+ prepareEHPad(BB, false);
+ else
+ prepareEHPad(BB, true, Index++);
+ }
+
+ // Cleanup pads don't need a personality function call.
+ for (auto *BB : CleanupPads)
+ prepareEHPad(BB, false);
+
+ return true;
}
// Prepare an EH pad for Wasm EH handling. If NeedPersonality is false, Index is
// ignored.
void WasmEHPrepare::prepareEHPad(BasicBlock *BB, bool NeedPersonality,
- bool NeedLSDA, unsigned Index) {
- if (!IsEHPadFunctionsSetUp) {
- IsEHPadFunctionsSetUp = true;
- setupEHPadFunctions(*BB->getParent());
- }
+ unsigned Index) {
assert(BB->isEHPad() && "BB is not an EHPad!");
IRBuilder<> IRB(BB->getContext());
IRB.SetInsertPoint(&*BB->getFirstInsertionPt());
@@ -361,8 +280,8 @@ void WasmEHPrepare::prepareEHPad(BasicBlock *BB, bool NeedPersonality,
}
}
- // Cleanup pads w/o __clang_call_terminate call do not have any of
- // wasm.get.exception() or wasm.get.ehselector() calls. We need to do nothing.
+ // Cleanup pads do not have any of wasm.get.exception() or
+ // wasm.get.ehselector() calls. We need to do nothing.
if (!GetExnCI) {
assert(!GetSelectorCI &&
"wasm.get.ehselector() cannot exist w/o wasm.get.exception()");
@@ -399,9 +318,11 @@ void WasmEHPrepare::prepareEHPad(BasicBlock *BB, bool NeedPersonality,
IRB.CreateStore(IRB.getInt32(Index), LPadIndexField);
auto *CPI = cast<CatchPadInst>(FPI);
- if (NeedLSDA)
- // Pseudocode: __wasm_lpad_context.lsda = wasm.lsda();
- IRB.CreateStore(IRB.CreateCall(LSDAF), LSDAField);
+ // TODO Sometimes storing the LSDA address every time is not necessary, in
+ // case it is already set in a dominating EH pad and there is no function call
+ // between from that EH pad to here. Consider optimizing those cases.
+ // Pseudocode: __wasm_lpad_context.lsda = wasm.lsda();
+ IRB.CreateStore(IRB.CreateCall(LSDAF), LSDAField);
// Pseudocode: _Unwind_CallPersonality(exn);
CallInst *PersCI = IRB.CreateCall(CallPersonalityF, CatchCI,
@@ -436,9 +357,9 @@ void llvm::calculateWasmEHInfo(const Function *F, WasmEHFuncInfo &EHInfo) {
const Instruction *UnwindPad = UnwindBB->getFirstNonPHI();
if (const auto *CatchSwitch = dyn_cast<CatchSwitchInst>(UnwindPad))
// Currently there should be only one handler per a catchswitch.
- EHInfo.setEHPadUnwindDest(&BB, *CatchSwitch->handlers().begin());
+ EHInfo.setUnwindDest(&BB, *CatchSwitch->handlers().begin());
else // cleanuppad
- EHInfo.setEHPadUnwindDest(&BB, UnwindBB);
+ EHInfo.setUnwindDest(&BB, UnwindBB);
}
}
}
generated by cgit v1.3 (git 2.53.0) at 2026-09-04 22:19:33 +0000