[clang][modules] Fix CodeGen options that can affect the AST. (#78816)

`OptimizationLevel` and `OptimizeSize` can affect the generated AST. They indirectly affect the `Optimize` and `OptimizeSize` frontend options, which in turn set predefined macro definitions.

This fixes rdar://121228252.

clang/include/clang/Basic/CodeGenOptions.def

@@ -12,6 +12,9 @@
 // that have enumeration type and VALUE_CODEGENOPT is a code
 // generation option that describes a value rather than a flag.
 //
+// AFFECTING_VALUE_CODEGENOPT is used for code generation options that can
+// affect the AST.
+//
 //===----------------------------------------------------------------------===//
 #ifndef CODEGENOPT
 #  error Define the CODEGENOPT macro to handle language options
@@ -27,6 +30,11 @@ CODEGENOPT(Name, Bits, Default)
 CODEGENOPT(Name, Bits, Default)
 #endif
 
+#ifndef AFFECTING_VALUE_CODEGENOPT
+#  define AFFECTING_VALUE_CODEGENOPT(Name, Bits, Default) \
+VALUE_CODEGENOPT(Name, Bits, Default)
+#endif
+
 CODEGENOPT(DisableIntegratedAS, 1, 0) ///< -no-integrated-as
 CODEGENOPT(RelaxELFRelocations, 1, 1) ///< -Wa,-mrelax-relocations={yes,no}
 CODEGENOPT(AsmVerbose        , 1, 0) ///< -dA, -fverbose-asm.
@@ -193,8 +201,10 @@ ENUM_CODEGENOPT(ObjCDispatchMethod, ObjCDispatchMethodKind, 2, Legacy)
 CODEGENOPT(ObjCConvertMessagesToRuntimeCalls , 1, 1)
 CODEGENOPT(ObjCAvoidHeapifyLocalBlocks, 1, 0)
 
-VALUE_CODEGENOPT(OptimizationLevel, 2, 0) ///< The -O[0-3] option specified.
-VALUE_CODEGENOPT(OptimizeSize, 2, 0) ///< If -Os (==1) or -Oz (==2) is specified.
+
+// The optimization options affect frontend options, whicn in turn do affect the AST.
+AFFECTING_VALUE_CODEGENOPT(OptimizationLevel, 2, 0) ///< The -O[0-3] option specified.
+AFFECTING_VALUE_CODEGENOPT(OptimizeSize, 2, 0) ///< If -Os (==1) or -Oz (==2) is specified.
 
 CODEGENOPT(AtomicProfileUpdate , 1, 0) ///< Set -fprofile-update=atomic
 /// Choose profile instrumenation kind or no instrumentation.
@@ -437,3 +447,4 @@ CODEGENOPT(CtorDtorReturnThis, 1, 0)
 #undef CODEGENOPT
 #undef ENUM_CODEGENOPT
 #undef VALUE_CODEGENOPT
+#undef AFFECTING_VALUE_CODEGENOPT

clang/lib/Basic/CodeGenOptions.cpp

@@ -27,6 +27,8 @@ void CodeGenOptions::resetNonModularOptions(StringRef ModuleFormat) {
 #define ENUM_DEBUGOPT(Name, Type, Bits, Default)
 #define CODEGENOPT(Name, Bits, Default) Name = Default;
 #define ENUM_CODEGENOPT(Name, Type, Bits, Default) set##Name(Default);
+// Do not reset AST affecting code generation options.
+#define AFFECTING_VALUE_CODEGENOPT(Name, Bits, Default)
 #include "clang/Basic/CodeGenOptions.def"
 
   // Next reset all debug options that can always be reset, because they never

clang/test/ClangScanDeps/strip-codegen-args.m

@@ -5,11 +5,14 @@
 // RUN: clang-scan-deps -compilation-database %t/cdb1.json -format experimental-full > %t/result1.txt
 // RUN: FileCheck %s -input-file %t/result1.txt
 
-// This tests that codegen option that do not affect the AST or generation of a module are removed. 
+// This tests that codegen option that do not affect the AST or generation of a
+// module are removed. It also tests that the optimization options that affect
+// the AST are not reset to -O0.
 
 // CHECK:        "modules": [
 // CHECK-NEXT:     {
 // CHECK:            "command-line": [
+// CHECK-NOT:          "-O0"
 // CHECK-NOT:          "-flto"
 // CHECK-NOT:          "-fno-autolink"
 // CHECK-NOT:          "-mrelax-relocations=no"
@@ -23,17 +26,17 @@
 [
   {
     "directory": "DIR",
-    "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -flto -fno-autolink -Xclang -mrelax-relocations=no -fsyntax-only DIR/t1.m",
+    "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -O2 -flto -fno-autolink -Xclang -mrelax-relocations=no -fsyntax-only DIR/t1.m",
     "file": "DIR/t1.m"
   },
   {
     "directory": "DIR",
-    "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -flto=thin -fautolink -fsyntax-only DIR/t2.m",
+    "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -O2 -flto=thin -fautolink -fsyntax-only DIR/t2.m",
     "file": "DIR/t2.m"
   },
   {
     "directory": "DIR",
-    "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -flto=full -fsyntax-only DIR/t3.m",
+    "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -O2 -flto=full -fsyntax-only DIR/t3.m",
     "file": "DIR/t2.m"
   }
 ]