Add support for other typeinfo encodings in the ExceptionDemo.

The old jit always uses DW_EH_PE_absptr, but MCJIT can use other encodings.
This is in preparation for adding EH support to MCJIT, but not directly
related, so I am committing it first.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180883 91177308-0d34-0410-b5e6-96231b3b80d8

examples/ExceptionDemo/ExceptionDemo.cpp

@@ -418,6 +418,30 @@ static uintptr_t readSLEB128(const uint8_t **data) {
   return result;
 }
 
+unsigned getEncodingSize(uint8_t Encoding) {
+  if (Encoding == llvm::dwarf::DW_EH_PE_omit)
+    return 0;
+
+  switch (Encoding & 0x0F) {
+  case llvm::dwarf::DW_EH_PE_absptr:
+    return sizeof(uintptr_t);
+  case llvm::dwarf::DW_EH_PE_udata2:
+    return sizeof(uint16_t);
+  case llvm::dwarf::DW_EH_PE_udata4:
+    return sizeof(uint32_t);
+  case llvm::dwarf::DW_EH_PE_udata8:
+    return sizeof(uint64_t);
+  case llvm::dwarf::DW_EH_PE_sdata2:
+    return sizeof(int16_t);
+  case llvm::dwarf::DW_EH_PE_sdata4:
+    return sizeof(int32_t);
+  case llvm::dwarf::DW_EH_PE_sdata8:
+    return sizeof(int64_t);
+  default:
+    // not supported
+    abort();
+  }
+}
 
 /// Read a pointer encoded value and advance pointer
 /// See Variable Length Data in:
@@ -523,7 +547,8 @@ static uintptr_t readEncodedPointer(const uint8_t **data, uint8_t encoding) {
 /// @returns whether or not a type info was found. False is returned if only
 ///          a cleanup was found
 static bool handleActionValue(int64_t *resultAction,
-                              struct OurExceptionType_t **classInfo,
+                              uint8_t TTypeEncoding,
+                              const uint8_t *ClassInfo,
                               uintptr_t actionEntry,
                               uint64_t exceptionClass,
                               struct _Unwind_Exception *exceptionObject) {
@@ -572,16 +597,22 @@ static bool handleActionValue(int64_t *resultAction,
 
     // Note: A typeOffset == 0 implies that a cleanup llvm.eh.selector
     //       argument has been matched.
-    if ((typeOffset > 0) &&
-        (type == (classInfo[-typeOffset])->type)) {
+    if (typeOffset > 0) {
 #ifdef DEBUG
       fprintf(stderr,
               "handleActionValue(...):actionValue <%d> found.\n",
               i);
 #endif
-      *resultAction = i + 1;
-      ret = true;
-      break;
+      unsigned EncSize = getEncodingSize(TTypeEncoding);
+      const uint8_t *EntryP = ClassInfo - typeOffset * EncSize;
+      uintptr_t P = readEncodedPointer(&EntryP, TTypeEncoding);
+      struct OurExceptionType_t *ThisClassInfo =
+        reinterpret_cast<struct OurExceptionType_t *>(P);
+      if (ThisClassInfo->type == type) {
+        *resultAction = i + 1;
+        ret = true;
+        break;
+      }
     }
 
 #ifdef DEBUG
@@ -633,7 +664,7 @@ static _Unwind_Reason_Code handleLsda(int version,
   // emitted dwarf code)
   uintptr_t funcStart = _Unwind_GetRegionStart(context);
   uintptr_t pcOffset = pc - funcStart;
-  struct OurExceptionType_t **classInfo = NULL;
+  const uint8_t *ClassInfo = NULL;
 
   // Note: See JITDwarfEmitter::EmitExceptionTable(...) for corresponding
   //       dwarf emission
@@ -653,7 +684,7 @@ static _Unwind_Reason_Code handleLsda(int version,
     // were flagged by type info arguments to llvm.eh.selector
     // intrinsic
     classInfoOffset = readULEB128(&lsda);
-    classInfo = (struct OurExceptionType_t**) (lsda + classInfoOffset);
+    ClassInfo = lsda + classInfoOffset;
   }
 
   // Walk call-site table looking for range that
@@ -714,7 +745,8 @@ static _Unwind_Reason_Code handleLsda(int version,
 
       if (actionEntry) {
         exceptionMatched = handleActionValue(&actionValue,
-                                             classInfo,
+                                             ttypeEncoding,
+                                             ClassInfo,
                                              actionEntry,
                                              exceptionClass,
                                              exceptionObject);