[llvm] [AMDGPU] Add disassembler diagnostics for invalid kernel descriptors (PR #87400)

[Matt Arsenault via llvm-commits]

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@@ -2051,33 +2051,30 @@ disassembleObject(ObjectFile &Obj, const ObjectFile &DbgObj,
       for (size_t SHI = 0; SHI < SymbolsHere.size(); ++SHI) {
         SymbolInfoTy Symbol = SymbolsHere[SHI];
 
-        Error Err = Error::success();
-        bool Responded = DT->DisAsm->onSymbolStart(
-            Symbol, Size, Bytes.slice(Start, End - Start), SectionAddr + Start,
-            Err);
+        Expected<bool> RespondedOrErr = DT->DisAsm->onSymbolStart(
+            Symbol, Size, Bytes.slice(Start, End - Start), SectionAddr + Start);
 
-        if (!Responded) {
+        if (RespondedOrErr && !*RespondedOrErr) {
           // This symbol didn't trigger any interesting handling. Try the other
-          // symbols defined at this address. Errors can only be returned if the
-          // disassembler responds.
-          cantFail(std::move(Err));
+          // symbols defined at this address.
           continue;
         }
 
-        // If onSymbolStart responded and set Err, that means it identified some
+        // If onSymbolStart returned an Error, that means it identified some
         // kind of special data at this address, but wasn't able to disassemble
         // it meaningfully. So we fall back to printing the error out and
         // disassembling the failed region as bytes, assuming that the target
         // detected the failure before printing anything.
         //
-        // Either way, 'Size' will have been set to the amount of data covered
-        // by whatever prologue the target identified. So we advance our own
-        // position to beyond that. Sometimes that will be the entire distance
-        // to the next symbol, and sometimes it will be just a prologue and we
-        // should start disassembling instructions from where it left off.
-
-        if (Err) {
-          std::string ErrMsgStr = toString(std::move(Err));
+        // Regardless of whether onSymbolStart returned an Error or true, 'Size'
+        // will have been set to the amount of data covered by whatever prologue
+        // the target identified. So we advance our own position to beyond that.
+        // Sometimes that will be the entire distance to the next symbol, and
+        // sometimes it will be just a prologue and we should start
+        // disassembling instructions from where it left off.
+
+        if (!RespondedOrErr) {
+          std::string ErrMsgStr = toString(RespondedOrErr.takeError());
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arsenm wrote:

Defer the toString until printing. Can the << directly consume the error without it?

https://github.com/llvm/llvm-project/pull/87400