Revert "Revert "Revert "[Flang][Driver] Add a flag to control zero initializa…" (#123330)

Reverts #123097

Reverting due to buildbot failure
https://lab.llvm.org/buildbot/#/builders/89/builds/14577.

Author: kiranchandramohan

clang/include/clang/Driver/Options.td

@@ -3505,11 +3505,6 @@ def fno_struct_path_tbaa : Flag<["-"], "fno-struct-path-tbaa">, Group<f_Group>;
 def fno_strict_enums : Flag<["-"], "fno-strict-enums">, Group<f_Group>;
 def fno_strict_overflow : Flag<["-"], "fno-strict-overflow">, Group<f_Group>,
   Visibility<[ClangOption, FlangOption]>;
-defm init_global_zero : BoolOptionWithoutMarshalling<"f", "init-global-zero",
-  PosFlag<SetTrue, [], [FlangOption, FC1Option],
-          "Zero initialize globals without default initialization (default)">,
-  NegFlag<SetFalse, [], [FlangOption, FC1Option],
-          "Do not zero initialize globals without default initialization">>;
 def fno_pointer_tbaa : Flag<["-"], "fno-pointer-tbaa">, Group<f_Group>;
 def fno_temp_file : Flag<["-"], "fno-temp-file">, Group<f_Group>,
   Visibility<[ClangOption, CC1Option, CLOption, DXCOption]>, HelpText<

clang/lib/Driver/ToolChains/Flang.cpp

@@ -155,10 +155,8 @@ void Flang::addCodegenOptions(const ArgList &Args,
                    options::OPT_flang_deprecated_no_hlfir,
                    options::OPT_fno_ppc_native_vec_elem_order,
                    options::OPT_fppc_native_vec_elem_order,
-                   options::OPT_finit_global_zero,
-                   options::OPT_fno_init_global_zero, options::OPT_ftime_report,
-                   options::OPT_ftime_report_EQ, options::OPT_funroll_loops,
-                   options::OPT_fno_unroll_loops});
+                   options::OPT_ftime_report, options::OPT_ftime_report_EQ,
+                   options::OPT_funroll_loops, options::OPT_fno_unroll_loops});
 }
 
 void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {

flang/include/flang/Lower/LoweringOptions.def

@@ -44,8 +44,5 @@ ENUM_LOWERINGOPT(IntegerWrapAround, unsigned, 1, 0)
 /// If false, assume that the shapes/types/allocation-status match.
 ENUM_LOWERINGOPT(ReallocateLHS, unsigned, 1, 1)
 
-/// If true, initialize globals without initialization to zero.
-/// On by default.
-ENUM_LOWERINGOPT(InitGlobalZero, unsigned, 1, 1)
 #undef LOWERINGOPT
 #undef ENUM_LOWERINGOPT

flang/lib/Frontend/CompilerInvocation.cpp

@@ -1377,14 +1377,6 @@ bool CompilerInvocation::createFromArgs(
     invoc.loweringOpts.setNoPPCNativeVecElemOrder(true);
   }
 
-  // -f[no-]init-global-zero
-  if (args.hasFlag(clang::driver::options::OPT_finit_global_zero,
-                   clang::driver::options::OPT_fno_init_global_zero,
-                   /*default=*/true))
-    invoc.loweringOpts.setInitGlobalZero(true);
-  else
-    invoc.loweringOpts.setInitGlobalZero(false);
-
   // Preserve all the remark options requested, i.e. -Rpass, -Rpass-missed or
   // -Rpass-analysis. This will be used later when processing and outputting the
   // remarks generated by LLVM in ExecuteCompilerInvocation.cpp.

flang/lib/Lower/ConvertVariable.cpp

@@ -635,11 +635,7 @@ static fir::GlobalOp defineGlobal(Fortran::lower::AbstractConverter &converter,
       global.setLinkName(builder.createCommonLinkage());
     Fortran::lower::createGlobalInitialization(
         builder, global, [&](fir::FirOpBuilder &builder) {
-          mlir::Value initValue;
-          if (converter.getLoweringOptions().getInitGlobalZero())
-            initValue = builder.create<fir::ZeroOp>(loc, symTy);
-          else
-            initValue = builder.create<fir::UndefOp>(loc, symTy);
+          mlir::Value initValue = builder.create<fir::ZeroOp>(loc, symTy);
           builder.create<fir::HasValueOp>(loc, initValue);
         });
   }

flang/test/Driver/fno-zero-init.f90

@@ -234,11 +234,6 @@ static llvm::cl::opt<bool> integerWrapAround(
     llvm::cl::desc("Treat signed integer overflow as two's complement"),
     llvm::cl::init(false));
 
-static llvm::cl::opt<bool> initGlobalZero(
-    "finit-global-zero",
-    llvm::cl::desc("Zero initialize globals without default initialization"),
-    llvm::cl::init(true));
-
 static llvm::cl::opt<bool>
     reallocateLHS("frealloc-lhs",
                   llvm::cl::desc("Follow Fortran 2003 rules for (re)allocating "
@@ -386,7 +381,6 @@ static llvm::LogicalResult convertFortranSourceToMLIR(
   loweringOptions.setNoPPCNativeVecElemOrder(enableNoPPCNativeVecElemOrder);
   loweringOptions.setLowerToHighLevelFIR(useHLFIR || emitHLFIR);
   loweringOptions.setIntegerWrapAround(integerWrapAround);
-  loweringOptions.setInitGlobalZero(initGlobalZero);
   loweringOptions.setReallocateLHS(reallocateLHS);
   std::vector<Fortran::lower::EnvironmentDefault> envDefaults = {};
   Fortran::frontend::TargetOptions targetOpts;