FP math settings for static duration initialization - work in progress

[mibintc]

Summary

When compiling this C test case with -frounding-math there is an error diagnostic due to the rounding

float F3d = 0x1.000001p0;

This patch resets the FP settings around the initialization expression

[sepavloff]

Please look at D88498.

[mibintc]

refer to https://reviews.llvm.org/D88498

clang/lib/Parse/ParseDecl.cpp

InitializerScopeRAII(Parser &P, Declarator &D, Decl *ThisDecl)
       if (ThisDecl && P.getLangOpts().CPlusPlus) {
         Scope *S = nullptr;
         if (D.getCXXScopeSpec().isSet()) {
           P.EnterScope(0);
           S = P.getCurScope();
         }
         P.Actions.ActOnCXXEnterDeclInitializer(S, ThisDecl);
       }
+      auto ThisVarDecl = dyn_cast_or_null<VarDecl>(ThisDecl);
+      if (ThisVarDecl) {
+        FPOptionsOverride NewFPFeatures;
+        NewFPFeatures.setRoundingModeOverride(llvm::RoundingMode::NearestTiesToEven);
+        P.Actions.FpPragmaStack.Act(ThisDecl->getLocation(),
+                          Sema::PSK_Push_Set, StringRef(), NewFPFeatures);
+      }
+    }
+    ~InitializerScopeRAII() {
+      pop();
+      auto ThisVarDecl = dyn_cast_or_null<VarDecl>(ThisDecl);
+      if (ThisVarDecl) {
+        FPOptionsOverride NewFPFeatures;
+        P.Actions.FpPragmaStack.Act(SourceLocation(),
+                        Sema::PSK_Pop, StringRef(), NewFPFeatures);
+      }
     }
-    ~InitializerScopeRAII() { pop(); }
     void pop() {
       if (ThisDecl && P.getLangOpts().CPlusPlus) {
         Scope *S = nullptr;
         if (D.getCXXScopeSpec().isSet())
           S = P.getCurScope();
         P.Actions.ActOnCXXExitDeclInitializer(S, ThisDecl);
         if (S)
           P.ExitScope();