[RuntimeDyld] Improve error diagnostic in RuntimeDyldChecker.

The compiler often emits assembler-local labels (beginning with 'L') for use in
relocation expressions, however these aren't included in the object files.
Teach RuntimeDyldChecker to warn the user if they try to use one of these in an
expression, since it will never work.

llvm-svn: 212777

1 files changed, 15 insertions, 4 deletions

diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp
index 190bbbf93ff..b10ec360aa5 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp
@@ -199,7 +199,7 @@ namespace llvm {
       StringRef Symbol;
       std::tie(Symbol, RemainingExpr) = parseSymbol(RemainingExpr);
 
-      if (!Checker.checkSymbolIsValidForLoad(Symbol))
+      if (!Checker.isSymbolValid(Symbol))
         return std::make_pair(EvalResult(("Cannot decode unknown symbol '" +
                                           Symbol + "'").str()),
                               "");
@@ -268,7 +268,7 @@ namespace llvm {
       StringRef Symbol;
       std::tie(Symbol, RemainingExpr) = parseSymbol(RemainingExpr);
 
-      if (!Checker.checkSymbolIsValidForLoad(Symbol))
+      if (!Checker.isSymbolValid(Symbol))
         return std::make_pair(EvalResult(("Cannot decode unknown symbol '"
                                           + Symbol + "'").str()),
                               "");
@@ -304,6 +304,17 @@ namespace llvm {
       else if (Symbol == "next_pc")
         return evalNextPC(RemainingExpr);
 
+      if (!Checker.isSymbolValid(Symbol)) {
+        std::string ErrMsg("No known address for symbol '");
+        ErrMsg += Symbol;
+        ErrMsg += "'";
+        if (Symbol.startswith("L"))
+          ErrMsg += " (this appears to be an assembler local label - "
+                    " perhaps drop the 'L'?)";
+
+        return std::make_pair(EvalResult(ErrMsg), "");
+      }
+
       // Looks like a plain symbol reference.
       return std::make_pair(EvalResult(Checker.getSymbolAddress(Symbol)),
                             RemainingExpr);
@@ -397,7 +408,7 @@ namespace llvm {
       StringRef Symbol;
       std::tie(Symbol, RemainingExpr) = parseSymbol(RemainingExpr);
 
-      if (!Checker.checkSymbolIsValidForLoad(Symbol))
+      if (!Checker.isSymbolValid(Symbol))
         return std::make_pair(EvalResult(("Cannot dereference unknown symbol '"
                                           + Symbol + "'").str()),
                               "");
@@ -612,7 +623,7 @@ bool RuntimeDyldChecker::checkAllRulesInBuffer(StringRef RulePrefix,
   return DidAllTestsPass && (NumRules != 0);
 }
 
-bool RuntimeDyldChecker::checkSymbolIsValidForLoad(StringRef Symbol) const {
+bool RuntimeDyldChecker::isSymbolValid(StringRef Symbol) const {
   return RTDyld.getSymbolAddress(Symbol) != nullptr;
 }