[oslog] Fix bug where OSLog was not invalidating any state that it was changing.

This is important both for correctness reasons and for triaging reasons. The
correctness is obvious, but for those unaware there are many triaging utilities
that only verify or print pass output if the pass makes a change as indicated by
invalidating state.

lib/SILOptimizer/Mandatory/OSLogOptimization.cpp

@@ -1063,7 +1063,7 @@ static bool checkOSLogMessageIsConstant(SingleValueInstruction *osLogMessage,
 
 /// Constant evaluate instructions starting from 'start' and fold the uses
 /// of the value 'oslogMessage'. Stop when oslogMessageValue is released.
-static void constantFold(SILInstruction *start,
+static bool constantFold(SILInstruction *start,
                          SingleValueInstruction *oslogMessage,
                          unsigned assertConfig) {
   SILFunction *fun = start->getFunction();
@@ -1077,7 +1077,7 @@ static void constantFold(SILInstruction *start,
 
   auto errorInfo = collectConstants(state);
   if (errorInfo) // Evaluation failed with diagnostics.
-    return;
+    return false;
 
   // At this point, the `OSLogMessage` instance should be mapped to a constant
   // value in the interpreter state. If this is not the case, it means the
@@ -1085,9 +1085,10 @@ static void constantFold(SILInstruction *start,
   // incorrect. Detect and diagnose this scenario.
   bool errorDetected = checkOSLogMessageIsConstant(oslogMessage, state);
   if (errorDetected)
-    return;
+    return false;
 
   substituteConstants(state);
+  return true;
 }
 
 /// Given a call to the initializer of OSLogMessage, which conforms to
@@ -1283,13 +1284,20 @@ class OSLogOptimization : public SILFunctionTransform {
       }
     }
 
+    bool madeChange = false;
+
     // Constant fold the uses of properties of OSLogMessage instance. Note that
     // the function body will change due to constant folding, after each
     // iteration.
     for (auto *oslogInit : oslogMessageInits) {
       SILInstruction *interpolationStart = beginOfInterpolation(oslogInit);
       assert(interpolationStart);
-      constantFold(interpolationStart, oslogInit, assertConfig);
+      madeChange |= constantFold(interpolationStart, oslogInit, assertConfig);
+    }
+
+    // TODO: Can we be more conservative here with our invalidation?
+    if (madeChange) {
+      invalidateAnalysis(SILAnalysis::InvalidationKind::FunctionBody);
     }
   }
 };