Merge commit fde5924dcc69 from llvm-project (by Serge Pavlov):

[clang] Reset FP options before template instantiation

  AST nodes that may depend on FP options keep them as a difference
  relative to the options outside the AST node. At the moment of
  instantiation the FP options may be different from the default values,
  defined by command-line option. In such case FP attributes would have
  unexpected values. For example, the code:

      template <class C> void func_01(int last, C) {
        func_01(last, int());
      }
      void func_02() { func_01(0, 1); }
      #pragma STDC FENV_ACCESS ON

  caused compiler crash, because template instantiation takes place at the
  end of translation unit, where pragma STDC FENV_ACCESS is in effect. As
  a result, code in the template instantiation would use constrained
  intrinsics while the function does not have StrictFP attribute.

  To solve this problem, FP attributes in Sema must be set to default
  values, defined by command line options.

  This change resolves https://github.com/llvm/llvm-project/issues/63542.

  Differential Revision: https://reviews.llvm.org/D154359

Requested by:	pkubaj
PR:		265755, 265758
MFC after:	1 month

contrib/llvm-project/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -5057,6 +5057,10 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
     // PushDeclContext because we don't have a scope.
     Sema::ContextRAII savedContext(*this, Function);
 
+    FPFeaturesStateRAII SavedFPFeatures(*this);
+    CurFPFeatures = FPOptions(getLangOpts());
+    FpPragmaStack.CurrentValue = FPOptionsOverride();
+
     if (addInstantiatedParametersToScope(Function, PatternDecl, Scope,
                                          TemplateArgs))
       return;