[WebAssembly] Improve EH/SjLj error messages

[aheejin]

Summary

This includes a function name and a relevant instruction in error
messages when possible, making them more helpful.

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

bool WebAssemblyLowerEmscriptenEHSjLj::runSjLjOnFunction(Function &F) {
   // Setjmp transformation
   SmallVector<PHINode *, 4> SetjmpRetPHIs;
   Function *SetjmpF = M.getFunction("setjmp");
   for (auto *U : make_early_inc_range(SetjmpF->users())) {
     auto *CB = cast<CallBase>(U);
     BasicBlock *BB = CB->getParent();
     if (BB->getParent() != &F) // in other function
       continue;
-    if (CB->getOperandBundle(LLVMContext::OB_funclet))
-      report_fatal_error(
-          "setjmp within a catch clause is not supported in Wasm EH");
+    if (CB->getOperandBundle(LLVMContext::OB_funclet)) {
+      std::string S;
+      raw_string_ostream SS(S);
+      SS << "In function " + F.getName() +
+                ": setjmp within a catch clause is not supported in Wasm EH:\n";
+      SS << *CB;
+      report_fatal_error(StringRef(SS.str()));
+    }
 
     CallInst *CI = nullptr;
     // setjmp cannot throw. So if it is an invoke, lower it to a call
     if (auto *II = dyn_cast<InvokeInst>(CB))
       CI = llvm::changeToCall(II);
     else
       CI = cast<CallInst>(CB);
 
void WebAssemblyLowerEmscriptenEHSjLj::handleLongjmpableCallsForEmscriptenSjLj(
   std::vector<BasicBlock *> BBs;
   for (BasicBlock &BB : F)
     BBs.push_back(&BB);
 
   // BBs.size() will change within the loop, so we query it every time
   for (unsigned I = 0; I < BBs.size(); I++) {
     BasicBlock *BB = BBs[I];
     for (Instruction &I : *BB) {
-      if (isa<InvokeInst>(&I))
-        report_fatal_error("When using Wasm EH with Emscripten SjLj, there is "
-                           "a restriction that `setjmp` function call and "
-                           "exception cannot be used within the same function");
+      if (isa<InvokeInst>(&I)) {
+        std::string S;
+        raw_string_ostream SS(S);
+        SS << "In function " << F.getName()
+           << ": When using Wasm EH with Emscripten SjLj, there is a "
+              "restriction that `setjmp` function call and exception cannot be "
+              "used within the same function:\n";
+        SS << I;
+        report_fatal_error(StringRef(SS.str()));
+      }
       auto *CI = dyn_cast<CallInst>(&I);
       if (!CI)
         continue;
 
       const Value *Callee = CI->getCalledOperand();
       if (!canLongjmp(Callee))
         continue;
       if (isEmAsmCall(Callee))

llvm/test/CodeGen/WebAssembly/wasm-eh-em-sjlj-error.ll

 declare void @longjmp(%struct.__jmp_buf_tag*, i32) #1
 declare i8* @malloc(i32)
 declare void @free(i8*)
 
 attributes #0 = { returns_twice }
 attributes #1 = { noreturn }
 attributes #2 = { nounwind }
 
-; CHECK: LLVM ERROR: When using Wasm EH with Emscripten SjLj, there is a restriction that `setjmp` function call and exception cannot be used within the same function
+; CHECK: LLVM ERROR: In function wasm_eh_emscripten_sjlj_error: When using Wasm EH with Emscripten SjLj, there is a restriction that `setjmp` function call and exception cannot be used within the same function
+; CHECK-NEXT: invoke void @foo()
+; CHECK-NEXT:         to label %try.cont unwind label %catch.dispatch

llvm/test/CodeGen/WebAssembly/wasm-eh-sjlj-setjmp-within-catch.ll

catch.start:                                      ; preds = %catch.dispatch
   %matches = icmp eq i32 %3, %4
   br i1 %matches, label %catch, label %rethrow
 
 catch:                                            ; preds = %catch.start
   %5 = call i8* @__cxa_begin_catch(i8* %2) #0 [ "funclet"(token %1) ]
   %6 = bitcast i8* %5 to i32*
   %7 = load i32, i32* %6, align 4
   %arraydecay = getelementptr inbounds [1 x %struct.__jmp_buf_tag], [1 x %struct.__jmp_buf_tag]* %buf, i32 0, i32 0
-; CHECK: LLVM ERROR: setjmp within a catch clause is not supported in Wasm EH
+; CHECK: LLVM ERROR: In function setjmp_within_catch: setjmp within a catch clause is not supported in Wasm EH
+; CHECK-NEXT: %call = invoke i32 @setjmp
   %call = invoke i32 @setjmp(%struct.__jmp_buf_tag* noundef %arraydecay) #2 [ "funclet"(token %1) ]
           to label %invoke.cont1 unwind label %ehcleanup
 
 invoke.cont1:                                     ; preds = %catch
   call void @__cxa_end_catch() #0 [ "funclet"(token %1) ]
   catchret from %1 to label %try.cont
 
 rethrow:                                          ; preds = %catch.start
   call void @llvm.wasm.rethrow() #1 [ "funclet"(token %1) ]
   unreachable
 
 try.cont:                                         ; preds = %entry, %invoke.cont1
   ret void
 
 ehcleanup:                                        ; preds = %catch
   %8 = cleanuppad within %1 []
   call void @__cxa_end_catch() #0 [ "funclet"(token %8) ]
   cleanupret from %8 unwind to caller
 }
 
-
 declare void @foo()
 declare i32 @__gxx_wasm_personality_v0(...)
 ; Function Attrs: nounwind
 declare i8* @llvm.wasm.get.exception(token) #0
 ; Function Attrs: nounwind
 declare i32 @llvm.wasm.get.ehselector(token) #0
 ; Function Attrs: nounwind
 declare i32 @llvm.eh.typeid.for(i8*) #0