[WebAssembly] Improve pseudocode in LowerEmscriptenEHSjLj

[aheejin]

Summary

Both __THREW__ and __threwValue are global variables, and we have
been distinguishing the global variable __THREW__ and the loaded value
%__THREW__.val in comments but not doing it for __threwValue. Made
the pseudocode comments consistent for both variables.

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

 ///
 /// 1) Assumes the existence of global variables: __THREW__, __threwValue
 ///    __THREW__ and __threwValue are defined in compiler-rt in Emscripten.
 ///    These variables are used for both exceptions and setjmp/longjmps.
 ///    __THREW__ indicates whether an exception or a longjmp occurred or not. 0
 ///    means nothing occurred, 1 means an exception occurred, and other numbers
 ///    mean a longjmp occurred. In the case of longjmp, __THREW__ variable
 ///    indicates the corresponding setjmp buffer the longjmp corresponds to.
+///    __threwValue is 0 for exceptions, and the argument to longjmp in case of
+///    longjmp.
 ///
 /// * Exception handling
 ///
 /// 2) We assume the existence of setThrew and setTempRet0/getTempRet0 functions
 ///    at link time. setThrew exists in Emscripten's compiler-rt:
 ///
 ///    void setThrew(uintptr_t threw, int value) {
 ///      if (__THREW__ == 0) {

 ///    order to make the post-setjmp BB the possible destination of longjmp BB.
 ///
 ///
 /// 4) Lower every call that might longjmp into
 ///      __THREW__ = 0;
 ///      call @__invoke_SIG(func, arg1, arg2)
 ///      %__THREW__.val = __THREW__;
 ///      __THREW__ = 0;
-///      if (%__THREW__.val != 0 & __threwValue != 0) {
+///      %__threwValue.val = __threwValue;
+///      if (%__THREW__.val != 0 & %__threwValue.val != 0) {
 ///        %label = testSetjmp(mem[%__THREW__.val], setjmpTable,
 ///                            setjmpTableSize);
 ///        if (%label == 0)
-///          emscripten_longjmp(%__THREW__.val, __threwValue);
-///        setTempRet0(__threwValue);
+///          emscripten_longjmp(%__THREW__.val, %__threwValue.val);
+///        setTempRet0(%__threwValue.val);
 ///      } else {
 ///        %label = -1;
 ///      }
 ///      longjmp_result = getTempRet0();
 ///      switch label {
 ///        label 1: goto post-setjmp BB 1
 ///        label 2: goto post-setjmp BB 2
 ///        ...
 ///        default: goto splitted next BB
 ///      }
 ///    testSetjmp examines setjmpTable to see if there is a matching setjmp
 ///    call. After calling an invoke wrapper, if a longjmp occurred, __THREW__
 ///    will be the address of matching jmp_buf buffer and __threwValue be the
-///    second argument to longjmp. mem[__THREW__.val] is a setjmp ID that is
+///    second argument to longjmp. mem[%__THREW__.val] is a setjmp ID that is
 ///    stored in saveSetjmp. testSetjmp returns a setjmp label, a unique ID to
 ///    each setjmp callsite. Label 0 means this longjmp buffer does not
 ///    correspond to one of the setjmp callsites in this function, so in this
 ///    case we just chain the longjmp to the caller. Label -1 means no longjmp
 ///    occurred. Otherwise we jump to the right post-setjmp BB based on the
 ///    label.
 ///
 ///===----------------------------------------------------------------------===//
return CalleeName == "emscripten_asm_const_int" ||
          CalleeName == "emscripten_asm_const_double" ||
          CalleeName == "emscripten_asm_const_int_sync_on_main_thread" ||
          CalleeName == "emscripten_asm_const_double_sync_on_main_thread" ||
          CalleeName == "emscripten_asm_const_async_on_main_thread";
 }
 
 // Generate testSetjmp function call seqence with preamble and postamble.
 // The code this generates is equivalent to the following JavaScript code:
-// if (%__THREW__.val != 0 & threwValue != 0) {
+// %__threwValue.val = __threwValue;
+// if (%__THREW__.val != 0 & %__threwValue.val != 0) {
 //   %label = _testSetjmp(mem[%__THREW__.val], setjmpTable, setjmpTableSize);
 //   if (%label == 0)
-//     emscripten_longjmp(%__THREW__.val, threwValue);
-//   setTempRet0(threwValue);
+//     emscripten_longjmp(%__THREW__.val, %__threwValue.val);
+//   setTempRet0(%__threwValue.val);
 // } else {
 //   %label = -1;
 // }
 // %longjmp_result = getTempRet0();
 //
 // As output parameters. returns %label, %longjmp_result, and the BB the last
 // instruction (%longjmp_result = ...) is in.
 void WebAssemblyLowerEmscriptenEHSjLj::wrapTestSetjmp(
     BasicBlock *BB, DebugLoc DL, Value *Threw, Value *SetjmpTable,
     Value *SetjmpTableSize, Value *&Label, Value *&LongjmpResult,
     BasicBlock *&EndBB) {
   Function *F = BB->getParent();
   Module *M = F->getParent();
   LLVMContext &C = M->getContext();
   IRBuilder<> IRB(C);
   IRB.SetCurrentDebugLocation(DL);
 
-  // if (%__THREW__.val != 0 & threwValue != 0)
+  // if (%__THREW__.val != 0 & %__threwValue.val != 0)
   IRB.SetInsertPoint(BB);
   BasicBlock *ThenBB1 = BasicBlock::Create(C, "if.then1", F);
   BasicBlock *ElseBB1 = BasicBlock::Create(C, "if.else1", F);
   BasicBlock *EndBB1 = BasicBlock::Create(C, "if.end", F);
   Value *ThrewCmp = IRB.CreateICmpNE(Threw, getAddrSizeInt(M, 0));
   Value *ThrewValue = IRB.CreateLoad(IRB.getInt32Ty(), ThrewValueGV,
                                      ThrewValueGV->getName() + ".val");
   Value *ThrewValueCmp = IRB.CreateICmpNE(ThrewValue, IRB.getInt32(0));
Value *ThrewPtr =
       IRB.CreateIntToPtr(Threw, getAddrPtrType(M), Threw->getName() + ".p");
   Value *LoadedThrew = IRB.CreateLoad(getAddrIntType(M), ThrewPtr,
                                       ThrewPtr->getName() + ".loaded");
   Value *ThenLabel = IRB.CreateCall(
       TestSetjmpF, {LoadedThrew, SetjmpTable, SetjmpTableSize}, "label");
   Value *Cmp2 = IRB.CreateICmpEQ(ThenLabel, IRB.getInt32(0));
   IRB.CreateCondBr(Cmp2, ThenBB2, EndBB2);
 
-  // emscripten_longjmp(%__THREW__.val, threwValue);
+  // emscripten_longjmp(%__THREW__.val, %__threwValue.val);
   IRB.SetInsertPoint(ThenBB2);
   IRB.CreateCall(EmLongjmpF, {Threw, ThrewValue});
   IRB.CreateUnreachable();
 
-  // setTempRet0(threwValue);
+  // setTempRet0(%__threwValue.val);
   IRB.SetInsertPoint(EndBB2);
   IRB.CreateCall(SetTempRet0Func, ThrewValue);
   IRB.CreateBr(EndBB1);
 
   IRB.SetInsertPoint(ElseBB1);
   IRB.CreateBr(EndBB1);
 
   // longjmp_result = getTempRet0();