commit fde5924dcc69fe814085482df259b8cfee236f2c
Author: Serge Pavlov <sepavloff@gmail.com>
Date:   Thu Jul 13 11:49:00 2023 +0700

    [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

diff --git clang/lib/Sema/SemaTemplateInstantiateDecl.cpp clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 492fe8ba1b14..9e5f85b0f916 100644
--- clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -5087,6 +5087,10 @@ 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;