summaryrefslogtreecommitdiff
path: root/llvm/lib/CodeGen/WasmEHPrepare.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'llvm/lib/CodeGen/WasmEHPrepare.cpp')
-rw-r--r--llvm/lib/CodeGen/WasmEHPrepare.cpp169
1 files changed, 119 insertions, 50 deletions
diff --git a/llvm/lib/CodeGen/WasmEHPrepare.cpp b/llvm/lib/CodeGen/WasmEHPrepare.cpp
index 1582f12ad5805..44f4fe2ff9b1f 100644
--- a/llvm/lib/CodeGen/WasmEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WasmEHPrepare.cpp
@@ -77,9 +77,11 @@
//
//===----------------------------------------------------------------------===//
+#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"
@@ -118,14 +120,17 @@ class WasmEHPrepare : public FunctionPass {
bool prepareEHPads(Function &F);
bool prepareThrows(Function &F);
- void prepareEHPad(BasicBlock *BB, bool NeedLSDA, unsigned Index = 0);
+ bool IsEHPadFunctionsSetUp = false;
+ void setupEHPadFunctions(Function &F);
+ void prepareEHPad(BasicBlock *BB, bool NeedPersonality, bool NeedLSDA = false,
+ unsigned Index = 0);
void prepareTerminateCleanupPad(BasicBlock *BB);
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;
@@ -136,11 +141,18 @@ public:
} // end anonymous namespace
char WasmEHPrepare::ID = 0;
-INITIALIZE_PASS(WasmEHPrepare, DEBUG_TYPE, "Prepare WebAssembly exceptions",
- false, false)
+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
@@ -153,18 +165,19 @@ 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) {
+static void eraseDeadBBsAndChildren(const Container &BBs, DomTreeUpdater *DTU) {
SmallVector<BasicBlock *, 8> WL(BBs.begin(), BBs.end());
while (!WL.empty()) {
auto *BB = WL.pop_back_val();
if (pred_begin(BB) != pred_end(BB))
continue;
WL.append(succ_begin(BB), succ_end(BB));
- DeleteDeadBlock(BB);
+ DeleteDeadBlock(BB, DTU);
}
}
bool WasmEHPrepare::runOnFunction(Function &F) {
+ IsEHPadFunctionsSetUp = false;
bool Changed = false;
Changed |= prepareThrows(F);
Changed |= prepareEHPads(F);
@@ -172,6 +185,9 @@ 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;
@@ -194,30 +210,102 @@ bool WasmEHPrepare::prepareThrows(Function &F) {
InstList.erase(std::next(BasicBlock::iterator(ThrowI)), InstList.end());
IRB.SetInsertPoint(BB);
IRB.CreateUnreachable();
- eraseDeadBBsAndChildren(Succs);
+ eraseDeadBBsAndChildren(Succs, &DTU);
}
return Changed;
}
bool WasmEHPrepare::prepareEHPads(Function &F) {
- Module &M = *F.getParent();
- IRBuilder<> IRB(F.getContext());
+ auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ bool Changed = false;
- SmallVector<BasicBlock *, 16> CatchPads;
- SmallVector<BasicBlock *, 16> CleanupPads;
- for (BasicBlock &BB : F) {
- if (!BB.isEHPad())
+ // 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)))
continue;
- auto *Pad = BB.getFirstNonPHI();
- if (isa<CatchPadInst>(Pad))
- CatchPads.push_back(&BB);
- else if (isa<CleanupPadInst>(Pad))
- CleanupPads.push_back(&BB);
+ 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);
+ }
}
- 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
@@ -252,29 +340,16 @@ bool WasmEHPrepare::prepareEHPads(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 LSDA
- if (CPI->getNumArgOperands() == 1 &&
- cast<Constant>(CPI->getArgOperand(0))->isNullValue())
- prepareEHPad(BB, false);
- else
- prepareEHPad(BB, true, Index++);
- }
-
- // Cleanup pads don't need LSDA.
- for (auto *BB : CleanupPads)
- prepareEHPad(BB, false);
-
- return true;
}
-// Prepare an EH pad for Wasm EH handling. If NeedLSDA is false, Index is
+// Prepare an EH pad for Wasm EH handling. If NeedPersonality is false, Index is
// ignored.
-void WasmEHPrepare::prepareEHPad(BasicBlock *BB, bool NeedLSDA,
- unsigned Index) {
+void WasmEHPrepare::prepareEHPad(BasicBlock *BB, bool NeedPersonality,
+ bool NeedLSDA, unsigned Index) {
+ if (!IsEHPadFunctionsSetUp) {
+ IsEHPadFunctionsSetUp = true;
+ setupEHPadFunctions(*BB->getParent());
+ }
assert(BB->isEHPad() && "BB is not an EHPad!");
IRBuilder<> IRB(BB->getContext());
IRB.SetInsertPoint(&*BB->getFirstInsertionPt());
@@ -283,9 +358,9 @@ void WasmEHPrepare::prepareEHPad(BasicBlock *BB, bool NeedLSDA,
Instruction *GetExnCI = nullptr, *GetSelectorCI = nullptr;
for (auto &U : FPI->uses()) {
if (auto *CI = dyn_cast<CallInst>(U.getUser())) {
- if (CI->getCalledValue() == GetExnF)
+ if (CI->getCalledOperand() == GetExnF)
GetExnCI = CI;
- if (CI->getCalledValue() == GetSelectorF)
+ if (CI->getCalledOperand() == GetSelectorF)
GetSelectorCI = CI;
}
}
@@ -304,7 +379,7 @@ void WasmEHPrepare::prepareEHPad(BasicBlock *BB, bool NeedLSDA,
// In case it is a catchpad with single catch (...) or a cleanuppad, we don't
// need to call personality function because we don't need a selector.
- if (!NeedLSDA) {
+ if (!NeedPersonality) {
if (GetSelectorCI) {
assert(GetSelectorCI->use_empty() &&
"wasm.get.ehselector() still has uses!");
@@ -322,14 +397,8 @@ void WasmEHPrepare::prepareEHPad(BasicBlock *BB, bool NeedLSDA,
// Pseudocode: __wasm_lpad_context.lpad_index = index;
IRB.CreateStore(IRB.getInt32(Index), LPadIndexField);
- // Store LSDA address only if this catchpad belongs to a top-level
- // catchswitch. If there is another catchpad that dominates this pad, we don't
- // need to store LSDA address again, because they are the same throughout the
- // function and have been already stored before.
- // TODO Can we not store LSDA address in user function but make libcxxabi
- // compute it?
auto *CPI = cast<CatchPadInst>(FPI);
- if (isa<ConstantTokenNone>(CPI->getCatchSwitch()->getParentPad()))
+ if (NeedLSDA)
// Pseudocode: __wasm_lpad_context.lsda = wasm.lsda();
IRB.CreateStore(IRB.CreateCall(LSDAF), LSDAField);
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-04 22:05:04 +0000