[Flang] Fix usage of uninitialized resolution variable

Recent Flang PowerPC intrinsics patch used resolution variable without checking if it exists first, causing segmentation faults in some scenarios. This patch checks that the resolution variable exists first before usage.

Reviewed By: DanielCChen

Differential Revision: https://reviews.llvm.org/D147616

diff --git a/flang/lib/Semantics/expression.cpp b/flang/lib/Semantics/expression.cpp
index 06226f2..cec936c 100644 (file)
--- a/flang/lib/Semantics/expression.cpp
+++ b/flang/lib/Semantics/expression.cpp
@@ -2518,12 +2518,12 @@ auto ExpressionAnalyzer::GetCalleeAndArguments(const parser::Name &name,
         mightBeStructureConstructor)};
     resolution = pair.first;
     dueToAmbiguity = pair.second;
-    if (context_.GetPPCBuiltinsScope() &&
-        resolution->name().ToString().rfind("__ppc_", 0) == 0) {
-      semantics::CheckPPCIntrinsic(
-          *symbol, *resolution, arguments, GetFoldingContext());
-    }
     if (resolution) {
+      if (context_.GetPPCBuiltinsScope() &&
+          resolution->name().ToString().rfind("__ppc_", 0) == 0) {
+        semantics::CheckPPCIntrinsic(
+            *symbol, *resolution, arguments, GetFoldingContext());
+      }
       // re-resolve name to the specific procedure
       name.symbol = const_cast<Symbol *>(resolution);
     }