[mips] Improve diagnostics for instruction mapping

This patch improves diagnostic for case when mapped instruction 
does not contain a field listed under RowFields.

Differential Revision: https://reviews.llvm.org/D41778

llvm-svn: 322004

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/utils/TableGen/CodeGenMapTable.cpp b/llvm/utils/TableGen/CodeGenMapTable.cpp
index 43348b622a7..e5b0426cdcc 100644
--- a/llvm/utils/TableGen/CodeGenMapTable.cpp
+++ b/llvm/utils/TableGen/CodeGenMapTable.cpp
@@ -243,7 +243,12 @@ void MapTableEmitter::buildRowInstrMap() {
     std::vector<Init*> KeyValue;
     ListInit *RowFields = InstrMapDesc.getRowFields();
     for (Init *RowField : RowFields->getValues()) {
-      Init *CurInstrVal = CurInstr->getValue(RowField)->getValue();
+      RecordVal *RecVal = CurInstr->getValue(RowField);
+      if (RecVal == nullptr)
+        PrintFatalError(CurInstr->getLoc(), "No value " +
+                        RowField->getAsString() + " found in \"" +
+                        CurInstr->getName() + "\" instruction description.");
+      Init *CurInstrVal = RecVal->getValue();
       KeyValue.push_back(CurInstrVal);
     }