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[WebAssembly] Fix bugs in WebAssemblyLowerEmscriptenExceptions pass
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* Delete extra '_' prefixes from JS library function names. fixImports()
  function in JS glue code deals with this for wasm.
* Change command-line option names in order to be consistent with
  asm.js.
* Add missing lowering code for llvm.eh.typeid.for intrinsics
* Delete commas in mangled function names
* Fix a function argument attributes bug. Because we add the pointer to
  the original callee as the first argument of invoke wrapper, all
  argument attribute indices have to be incremented by one.

Patch by Heejin Ahn

Differential Revision: https://reviews.llvm.org/D23258

llvm-svn: 278081
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@dschuff
dschuff committed Aug 9, 2016
1 parent 5f6ec06 commit 53b9af0
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125 changes: 92 additions & 33 deletions llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenExceptions.cpp
View file
Expand Up @@ -24,7 +24,7 @@
/// This pass does following things:
///
/// 1) Create three global variables: __THREW__, threwValue, and tempRet0.
/// tempRet0 will be set within ___cxa_find_matching_catch() function in
/// tempRet0 will be set within __cxa_find_matching_catch() function in
/// JS library, and __THREW__ and threwValue will be set in invoke wrappers
/// in JS glue code. For what invoke wrappers are, refer to 3).
///
Expand Down Expand Up @@ -77,31 +77,33 @@
/// %val = landingpad catch c1 catch c2 catch c3 ...
/// ... use %val ...
/// into
/// %fmc = call @___cxa_find_matching_catch_N(c1, c2, c3, ...)
/// %fmc = call @__cxa_find_matching_catch_N(c1, c2, c3, ...)
/// %val = {%fmc, tempRet0}
/// ... use %val ...
/// Here N is a number calculated based on the number of clauses.
/// Global variable tempRet0 is set within ___cxa_find_matching_catch() in
/// Global variable tempRet0 is set within __cxa_find_matching_catch() in
/// JS glue code.
///
/// 5) Lower
/// resume {%a, %b}
/// into
/// call @___resumeException(%a)
/// where ___resumeException() is a function in JS glue code.
/// call @__resumeException(%a)
/// where __resumeException() is a function in JS glue code.
///
/// TODO: Handle i64 types
/// 6) Lower
/// call @llvm.eh.typeid.for(type) (intrinsic)
/// into
/// call @llvm_eh_typeid_for(type)
/// llvm_eh_typeid_for function will be generated in JS glue code.
///
///===----------------------------------------------------------------------===//

#include "WebAssembly.h"
#include "llvm/ADT/IndexedMap.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/raw_ostream.h"
#include <set>

using namespace llvm;

Expand All @@ -114,9 +116,9 @@ class WebAssemblyLowerEmscriptenExceptions final : public ModulePass {
}

bool runOnFunction(Function &F);
// Returns ___cxa_find_matching_catch_N function, where N = NumClauses + 2.
// Returns __cxa_find_matching_catch_N function, where N = NumClauses + 2.
// This is because a landingpad instruction contains two more arguments,
// a personality function and a cleanup bit, and ___cxa_find_matching_catch_N
// a personality function and a cleanup bit, and __cxa_find_matching_catch_N
// functions are named after the number of arguments in the original
// landingpad instruction.
Function *getFindMatchingCatch(Module &M, unsigned NumClauses);
Expand All @@ -126,8 +128,9 @@ class WebAssemblyLowerEmscriptenExceptions final : public ModulePass {
GlobalVariable *ThrewGV; // __THREW__
GlobalVariable *ThrewValueGV; // threwValue
GlobalVariable *TempRet0GV; // tempRet0
Function *ResumeF;
// ___cxa_find_matching_catch_N functions.
Function *ResumeF; // __resumeException
Function *EHTypeIdF; // llvm_eh_typeid_for
// __cxa_find_matching_catch_N functions.
// Indexed by the number of clauses in an original landingpad instruction.
DenseMap<int, Function *> FindMatchingCatches;
// Map of <function signature string, invoke_ wrappers>
Expand Down Expand Up @@ -178,9 +181,9 @@ static inline std::string createGlobalValueName(const Module &M,

// Simple function name mangler.
// This function simply takes LLVM's string representation of parameter types
// concatenate them with '_'. There are non-alphanumeric characters but llc is
// ok with it, and we need to postprocess these names after the lowering phase
// anyway.
// and concatenate them with '_'. There are non-alphanumeric characters but llc
// is ok with it, and we need to postprocess these names after the lowering
// phase anyway.
static std::string getSignature(FunctionType *FTy) {
std::string Sig;
raw_string_ostream OS(Sig);
Expand All @@ -191,6 +194,9 @@ static std::string getSignature(FunctionType *FTy) {
OS << "_...";
Sig = OS.str();
Sig.erase(std::remove_if(Sig.begin(), Sig.end(), isspace), Sig.end());
// When s2wasm parses .s file, a comma means the end of an argument. So a
// mangled function name can contain any character but a comma.
std::replace(Sig.begin(), Sig.end(), ',', '.');
return Sig;
}

Expand All @@ -203,7 +209,7 @@ Function *WebAssemblyLowerEmscriptenExceptions::getFindMatchingCatch(
FunctionType *FTy = FunctionType::get(Int8PtrTy, Args, false);
Function *F = Function::Create(
FTy, GlobalValue::ExternalLinkage,
"___cxa_find_matching_catch_" + Twine(NumClauses + 2), &M);
"__cxa_find_matching_catch_" + Twine(NumClauses + 2), &M);
FindMatchingCatches[NumClauses] = F;
return F;
}
Expand Down Expand Up @@ -239,10 +245,12 @@ WebAssemblyLowerEmscriptenExceptions::getInvokeWrapper(Module &M,
}

bool WebAssemblyLowerEmscriptenExceptions::runOnModule(Module &M) {
IRBuilder<> Builder(M.getContext());
LLVMContext &C = M.getContext();
IRBuilder<> Builder(C);
IntegerType *Int1Ty = Builder.getInt1Ty();
PointerType *Int8PtrTy = Builder.getInt8PtrTy();
IntegerType *Int32Ty = Builder.getInt32Ty();
Type *VoidTy = Builder.getVoidTy();

// Create global variables __THREW__, threwValue, and tempRet0
ThrewGV = new GlobalVariable(M, Int1Ty, false, GlobalValue::ExternalLinkage,
Expand All @@ -255,11 +263,15 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnModule(Module &M) {
M, Int32Ty, false, GlobalValue::ExternalLinkage, Builder.getInt32(0),
createGlobalValueName(M, "tempRet0"));

// Register ___resumeException function
Type *VoidTy = Type::getVoidTy(M.getContext());
// Register __resumeException function
FunctionType *ResumeFTy = FunctionType::get(VoidTy, Int8PtrTy, false);
ResumeF = Function::Create(ResumeFTy, GlobalValue::ExternalLinkage,
"___resumeException", &M);
"__resumeException", &M);

// Register llvm_eh_typeid_for function
FunctionType *EHTypeIdTy = FunctionType::get(Int32Ty, Int8PtrTy, false);
EHTypeIdF = Function::Create(EHTypeIdTy, GlobalValue::ExternalLinkage,
"llvm_eh_typeid_for", &M);

bool Changed = false;
for (Function &F : M) {
Expand All @@ -283,9 +295,9 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnModule(Module &M) {
Argument *Arg2 = &*(++F->arg_begin());
Arg1->setName("threw");
Arg2->setName("value");
BasicBlock *EntryBB = BasicBlock::Create(M.getContext(), "entry", F);
BasicBlock *ThenBB = BasicBlock::Create(M.getContext(), "if.then", F);
BasicBlock *EndBB = BasicBlock::Create(M.getContext(), "if.end", F);
BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
BasicBlock *ThenBB = BasicBlock::Create(C, "if.then", F);
BasicBlock *EndBB = BasicBlock::Create(C, "if.end", F);

Builder.SetInsertPoint(EntryBB);
Value *Threw = Builder.CreateLoad(ThrewGV, ThrewGV->getName() + ".val");
Expand All @@ -305,7 +317,7 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnModule(Module &M) {
FTy = FunctionType::get(VoidTy, Params, false);
F = Function::Create(FTy, GlobalValue::ExternalLinkage, "setTempRet0", &M);
F->arg_begin()->setName("value");
EntryBB = BasicBlock::Create(M.getContext(), "entry", F);
EntryBB = BasicBlock::Create(C, "entry", F);
Builder.SetInsertPoint(EntryBB);
Builder.CreateStore(&*F->arg_begin(), TempRet0GV);
Builder.CreateRetVoid();
Expand All @@ -315,10 +327,12 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnModule(Module &M) {

bool WebAssemblyLowerEmscriptenExceptions::runOnFunction(Function &F) {
Module &M = *F.getParent();
IRBuilder<> Builder(M.getContext());
LLVMContext &C = F.getContext();
IRBuilder<> Builder(C);
bool Changed = false;
SmallVector<Instruction *, 64> ToErase;
SmallPtrSet<LandingPadInst *, 32> LandingPads;
bool AllowExceptions = true; // will later change based on whitelist option

for (BasicBlock &BB : F) {
auto *II = dyn_cast<InvokeInst>(BB.getTerminator());
Expand All @@ -328,15 +342,16 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnFunction(Function &F) {
LandingPads.insert(II->getLandingPadInst());
Builder.SetInsertPoint(II);

if (canThrow(II->getCalledValue())) {
bool NeedInvoke = AllowExceptions && canThrow(II->getCalledValue());
if (NeedInvoke) {
// If we are calling a function that is noreturn, we must remove that
// attribute. The code we insert here does expect it to return, after we
// catch the exception.
if (II->doesNotReturn()) {
if (auto *F = dyn_cast<Function>(II->getCalledValue()))
F->removeFnAttr(Attribute::NoReturn);
AttributeSet NewAttrs = II->getAttributes();
NewAttrs.removeAttribute(M.getContext(), AttributeSet::FunctionIndex,
NewAttrs.removeAttribute(C, AttributeSet::FunctionIndex,
Attribute::NoReturn);
II->setAttributes(NewAttrs);
}
Expand All @@ -354,8 +369,32 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnFunction(Function &F) {
CallInst *NewCall = Builder.CreateCall(getInvokeWrapper(M, II), CallArgs);
NewCall->takeName(II);
NewCall->setCallingConv(II->getCallingConv());
NewCall->setAttributes(II->getAttributes());
NewCall->setDebugLoc(II->getDebugLoc());

// Because we added the pointer to the callee as first argument, all
// argument attribute indices have to be incremented by one.
SmallVector<AttributeSet, 8> AttributesVec;
const AttributeSet &InvokePAL = II->getAttributes();
CallSite::arg_iterator AI = II->arg_begin();
unsigned i = 1; // Argument attribute index starts from 1
for (unsigned e = II->getNumArgOperands(); i <= e; ++AI, ++i) {
if (InvokePAL.hasAttributes(i)) {
AttrBuilder B(InvokePAL, i);
AttributesVec.push_back(AttributeSet::get(C, i + 1, B));
}
}
// Add any return attributes.
if (InvokePAL.hasAttributes(AttributeSet::ReturnIndex))
AttributesVec.push_back(
AttributeSet::get(C, InvokePAL.getRetAttributes()));
// Add any function attributes.
if (InvokePAL.hasAttributes(AttributeSet::FunctionIndex))
AttributesVec.push_back(
AttributeSet::get(C, InvokePAL.getFnAttributes()));
// Reconstruct the AttributesList based on the vector we constructed.
AttributeSet NewCallPAL = AttributeSet::get(C, AttributesVec);
NewCall->setAttributes(NewCallPAL);

II->replaceAllUsesWith(NewCall);
ToErase.push_back(II);

Expand All @@ -374,8 +413,8 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnFunction(Function &F) {
CallInst *NewCall = Builder.CreateCall(II->getCalledValue(), CallArgs);
NewCall->takeName(II);
NewCall->setCallingConv(II->getCallingConv());
NewCall->setAttributes(II->getAttributes());
NewCall->setDebugLoc(II->getDebugLoc());
NewCall->setAttributes(II->getAttributes());
II->replaceAllUsesWith(NewCall);
ToErase.push_back(II);

Expand All @@ -399,7 +438,7 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnFunction(Function &F) {
Builder.SetInsertPoint(RI);
Value *Low = Builder.CreateExtractValue(Input, 0, "low");

// Create a call to ___resumeException function
// Create a call to __resumeException function
Value *Args[] = {Low};
Builder.CreateCall(ResumeF, Args);

Expand All @@ -409,6 +448,26 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnFunction(Function &F) {
}
}

// Process llvm.eh.typeid.for intrinsics
for (BasicBlock &BB : F) {
for (Instruction &I : BB) {
auto *CI = dyn_cast<CallInst>(&I);
if (!CI)
continue;
const Function *Callee = CI->getCalledFunction();
if (!Callee)
continue;
if (Callee->getIntrinsicID() != Intrinsic::eh_typeid_for)
continue;

Builder.SetInsertPoint(CI);
CallInst *NewCI =
Builder.CreateCall(EHTypeIdF, CI->getArgOperand(0), "typeid");
CI->replaceAllUsesWith(NewCI);
ToErase.push_back(CI);
}
}

// Look for orphan landingpads, can occur in blocks with no predecesors
for (BasicBlock &BB : F) {
Instruction *I = BB.getFirstNonPHI();
Expand Down Expand Up @@ -437,7 +496,7 @@ bool WebAssemblyLowerEmscriptenExceptions::runOnFunction(Function &F) {
FMCArgs.push_back(Clause);
}

// Create a call to ___cxa_find_matching_catch_N function
// Create a call to __cxa_find_matching_catch_N function
Function *FMCF = getFindMatchingCatch(M, FMCArgs.size());
CallInst *FMCI = Builder.CreateCall(FMCF, FMCArgs, "fmc");
Value *Undef = UndefValue::get(LPI->getType());
Expand Down
2 changes: 1 addition & 1 deletion llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
View file
Expand Up @@ -31,7 +31,7 @@ using namespace llvm;

// Emscripten's asm.js-style exception handling
static cl::opt<bool> EnableEmExceptionHandling(
"wasm-em-exception-handling",
"enable-emscripten-cxx-exceptions",
cl::desc("WebAssembly Emscripten-style exception handling"),
cl::init(false));

Expand Down
58 changes: 52 additions & 6 deletions llvm/test/CodeGen/WebAssembly/lower-em-exceptions.ll
View file
Expand Up @@ -30,17 +30,20 @@ lpad: ; preds = %entry
%2 = extractvalue { i8*, i32 } %0, 1
br label %catch.dispatch
; CHECK: lpad:
; CHECK-NEXT: %[[FMC:.*]] = call i8* @___cxa_find_matching_catch_4(i8* bitcast (i8** @_ZTIi to i8*), i8* null)
; CHECK-NEXT: %[[FMC:.*]] = call i8* @__cxa_find_matching_catch_4(i8* bitcast (i8** @_ZTIi to i8*), i8* null)
; CHECK-NEXT: %[[IVI1:.*]] = insertvalue { i8*, i32 } undef, i8* %[[FMC]], 0
; CHECK-NEXT: %[[TEMPRET0_VAL:.*]] = load i32, i32* @[[TEMPRET0]]
; CHECK-NEXT: %[[IVI2:.*]] = insertvalue { i8*, i32 } %[[IVI1]], i32 %[[TEMPRET0_VAL]], 1
; CHECK-NEXT: extractvalue { i8*, i32 } %[[IVI2]], 0
; CHECK-NEXT: extractvalue { i8*, i32 } %[[IVI2]], 1
; CHECK-NEXT: %[[CDR:.*]] = extractvalue { i8*, i32 } %[[IVI2]], 1

catch.dispatch: ; preds = %lpad
%3 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*))
%matches = icmp eq i32 %2, %3
br i1 %matches, label %catch1, label %catch
; CHECK: catch.dispatch:
; CHECK-NEXT: %[[TYPEID:.*]] = call i32 @llvm_eh_typeid_for(i8* bitcast (i8** @_ZTIi to i8*))
; CHECK-NEXT: %matches = icmp eq i32 %[[CDR]], %[[TYPEID]]

catch1: ; preds = %catch.dispatch
%4 = call i8* @__cxa_begin_catch(i8* %1)
Expand Down Expand Up @@ -81,7 +84,7 @@ lpad: ; preds = %entry
%2 = extractvalue { i8*, i32 } %0, 1
br label %filter.dispatch
; CHECK: lpad:
; CHECK-NEXT: %[[FMC:.*]] = call i8* @___cxa_find_matching_catch_4(i8* bitcast (i8** @_ZTIi to i8*), i8* bitcast (i8** @_ZTIc to i8*))
; CHECK-NEXT: %[[FMC:.*]] = call i8* @__cxa_find_matching_catch_4(i8* bitcast (i8** @_ZTIi to i8*), i8* bitcast (i8** @_ZTIc to i8*))
; CHECK-NEXT: %[[IVI1:.*]] = insertvalue { i8*, i32 } undef, i8* %[[FMC]], 0
; CHECK-NEXT: %[[TEMPRET0_VAL:.*]] = load i32, i32* @[[TEMPRET0]]
; CHECK-NEXT: %[[IVI2:.*]] = insertvalue { i8*, i32 } %[[IVI1]], i32 %[[TEMPRET0_VAL]], 1
Expand All @@ -104,11 +107,54 @@ eh.resume: ; preds = %filter.dispatch
; CHECK-NEXT: insertvalue
; CHECK-NEXT: %[[LPAD_VAL:.*]] = insertvalue
; CHECK-NEXT: %[[LOW:.*]] = extractvalue { i8*, i32 } %[[LPAD_VAL]], 0
; CHECK-NEXT: call void @___resumeException(i8* %[[LOW]])
; CHECK-NEXT: call void @__resumeException(i8* %[[LOW]])
; CHECK-NEXT: unreachable
}

; Test if argument attributes indices in newly created call instructions are correct
define void @arg_attributes() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
; CHECK-LABEL: @arg_attributes(
entry:
%0 = invoke noalias i8* @bar(i8 signext 1, i8 zeroext 2)
to label %invoke.cont unwind label %lpad
; CHECK: entry:
; CHECK-NEXT: store i1 false, i1* @[[__THREW__]]
; CHECK-NEXT: %0 = call noalias i8* @"__invoke_i8*_i8_i8"(i8* (i8, i8)* @bar, i8 signext 1, i8 zeroext 2)

invoke.cont: ; preds = %entry
br label %try.cont

lpad: ; preds = %entry
%1 = landingpad { i8*, i32 }
catch i8* bitcast (i8** @_ZTIi to i8*)
catch i8* null
%2 = extractvalue { i8*, i32 } %1, 0
%3 = extractvalue { i8*, i32 } %1, 1
br label %catch.dispatch

catch.dispatch: ; preds = %lpad
%4 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*))
%matches = icmp eq i32 %3, %4
br i1 %matches, label %catch1, label %catch

catch1: ; preds = %catch.dispatch
%5 = call i8* @__cxa_begin_catch(i8* %2)
%6 = bitcast i8* %5 to i32*
%7 = load i32, i32* %6, align 4
call void @__cxa_end_catch()
br label %try.cont

try.cont: ; preds = %catch, %catch1, %invoke.cont
ret void

catch: ; preds = %catch.dispatch
%8 = call i8* @__cxa_begin_catch(i8* %2)
call void @__cxa_end_catch()
br label %try.cont
}

declare void @foo(i32)
declare i8* @bar(i8, i8)

declare i32 @__gxx_personality_v0(...)
declare i32 @llvm.eh.typeid.for(i8*)
Expand All @@ -117,9 +163,9 @@ declare void @__cxa_end_catch()
declare void @__cxa_call_unexpected(i8*)

; JS glue functions and invoke wrappers registration
; CHECK: declare void @___resumeException(i8*)
; CHECK: declare void @__resumeException(i8*)
; CHECK: declare void @__invoke_void_i32(void (i32)*, i32)
; CHECK: declare i8* @___cxa_find_matching_catch_4(i8*, i8*)
; CHECK: declare i8* @__cxa_find_matching_catch_4(i8*, i8*)

; setThrew function creation
; CHECK-LABEL: define void @setThrew(i1 %threw, i32 %value) {
Expand Down

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