Reland "[Flang][Driver] Add a flag to control zero initialization" #123606

kiranchandramohan · 2025-01-20T12:44:30Z

Reverts #123330

… zero in…" This reverts commit 8a229f5.

llvmbot · 2025-01-20T12:45:04Z

@llvm/pr-subscribers-clang-driver

@llvm/pr-subscribers-clang

Author: Kiran Chandramohan (kiranchandramohan)

Changes

Reverts llvm/llvm-project#123330

Full diff: https://github.com/llvm/llvm-project/pull/123606.diff

9 Files Affected:

(modified) clang/include/clang/Driver/Options.td (+5)
(modified) clang/lib/Driver/ToolChains/Flang.cpp (+4-2)
(modified) flang/include/flang/Lower/LoweringOptions.def (+3)
(modified) flang/lib/Frontend/CompilerInvocation.cpp (+8)
(modified) flang/lib/Lower/ConvertVariable.cpp (+5-1)
(added) flang/test/Driver/fno-zero-init.f90 (+9)
(added) flang/test/Lower/zero_init.f90 (+20)
(added) flang/test/Lower/zero_init_default_init.f90 (+22)
(modified) flang/tools/bbc/bbc.cpp (+6)

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index d38dd2b4e3cf09..c4b9743597bb2e 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3505,6 +3505,11 @@ 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<
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 86ed25badfa2b7..9c1fd28a3a8a26 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -155,8 +155,10 @@ 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_ftime_report, options::OPT_ftime_report_EQ,
-                   options::OPT_funroll_loops, options::OPT_fno_unroll_loops});
+                   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});
 }
 
 void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
diff --git a/flang/include/flang/Lower/LoweringOptions.def b/flang/include/flang/Lower/LoweringOptions.def
index 5a6debfdffe030..396c91948be36b 100644
--- a/flang/include/flang/Lower/LoweringOptions.def
+++ b/flang/include/flang/Lower/LoweringOptions.def
@@ -44,5 +44,8 @@ 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
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 15b1e1e0a24881..3c6da4687f65d3 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -1377,6 +1377,14 @@ 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.
diff --git a/flang/lib/Lower/ConvertVariable.cpp b/flang/lib/Lower/ConvertVariable.cpp
index 9ee42d5cd88002..87236dc293ebbc 100644
--- a/flang/lib/Lower/ConvertVariable.cpp
+++ b/flang/lib/Lower/ConvertVariable.cpp
@@ -635,7 +635,11 @@ static fir::GlobalOp defineGlobal(Fortran::lower::AbstractConverter &converter,
       global.setLinkName(builder.createCommonLinkage());
     Fortran::lower::createGlobalInitialization(
         builder, global, [&](fir::FirOpBuilder &builder) {
-          mlir::Value initValue = builder.create<fir::ZeroOp>(loc, symTy);
+          mlir::Value initValue;
+          if (converter.getLoweringOptions().getInitGlobalZero())
+            initValue = builder.create<fir::ZeroOp>(loc, symTy);
+          else
+            initValue = builder.create<fir::UndefOp>(loc, symTy);
           builder.create<fir::HasValueOp>(loc, initValue);
         });
   }
diff --git a/flang/test/Driver/fno-zero-init.f90 b/flang/test/Driver/fno-zero-init.f90
new file mode 100644
index 00000000000000..2ffa10dd040d52
--- /dev/null
+++ b/flang/test/Driver/fno-zero-init.f90
@@ -0,0 +1,9 @@
+! Check that the driver passes through -f[no-]init-global-zero:
+! RUN: %flang -### -S -finit-global-zero %s -o - 2>&1 | FileCheck --check-prefix=CHECK-POS %s
+! RUN: %flang -### -S -fno-init-global-zero %s -o - 2>&1 | FileCheck --check-prefix=CHECK-NEG %s
+! Check that the compiler accepts -f[no-]init-global-zero:
+! RUN: %flang_fc1 -emit-hlfir -finit-global-zero %s -o -
+! RUN: %flang_fc1 -emit-hlfir -fno-init-global-zero %s -o -
+
+! CHECK-POS: "-fc1"{{.*}}"-finit-global-zero"
+! CHECK-NEG: "-fc1"{{.*}}"-fno-init-global-zero"
diff --git a/flang/test/Lower/zero_init.f90 b/flang/test/Lower/zero_init.f90
new file mode 100644
index 00000000000000..5ed6f2247de3b2
--- /dev/null
+++ b/flang/test/Lower/zero_init.f90
@@ -0,0 +1,20 @@
+! RUN: %flang_fc1 -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: %flang_fc1 -finit-global-zero -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: %flang_fc1 -fno-init-global-zero -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-NO-ZERO-INIT %s
+! RUN: bbc -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: bbc -finit-global-zero -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: bbc -finit-global-zero=false -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-NO-ZERO-INIT %s
+
+module m1
+  real :: x
+end module m1
+
+!CHECK-DEFAULT: fir.global @_QMm1Ex : f32 {
+!CHECK-DEFAULT:   %[[UNDEF:.*]] = fir.zero_bits f32
+!CHECK-DEFAULT:   fir.has_value %[[UNDEF]] : f32
+!CHECK-DEFAULT: }
+
+!CHECK-NO-ZERO-INIT: fir.global @_QMm1Ex : f32 {
+!CHECK-NO-ZERO-INIT:   %[[UNDEF:.*]] = fir.undefined f32
+!CHECK-NO-ZERO-INIT:   fir.has_value %[[UNDEF]] : f32
+!CHECK-NO-ZERO-INIT: }
diff --git a/flang/test/Lower/zero_init_default_init.f90 b/flang/test/Lower/zero_init_default_init.f90
new file mode 100644
index 00000000000000..e2d1f545e35a57
--- /dev/null
+++ b/flang/test/Lower/zero_init_default_init.f90
@@ -0,0 +1,22 @@
+! RUN: %flang_fc1 -emit-hlfir -o - %s | FileCheck %s
+! RUN: %flang_fc1 -finit-global-zero -emit-hlfir -o - %s | FileCheck %s
+! RUN: %flang_fc1 -fno-init-global-zero -emit-hlfir -o - %s | FileCheck %s
+! RUN: bbc -emit-hlfir -o - %s | FileCheck %s
+! RUN: bbc -finit-global-zero -emit-hlfir -o - %s | FileCheck %s
+! RUN: bbc -finit-global-zero=false -emit-hlfir -o - %s | FileCheck %s
+
+! Test that the flag does not affect globals with default init
+
+module m2
+  type val
+    integer :: my_val = 1
+  end type val
+  type(val) :: v1
+end module m2
+
+!CHECK:  fir.global @_QMm2Ev1 : !fir.type<_QMm2Tval{my_val:i32}> {
+!CHECK:    %[[V1:.*]] = fir.undefined !fir.type<_QMm2Tval{my_val:i32}>
+!CHECK:    %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK:    %[[V1_INIT:.*]] = fir.insert_value %[[V1]], %[[ONE]], ["my_val", !fir.type<_QMm2Tval{my_val:i32}>] : (!fir.type<_QMm2Tval{my_val:i32}>, i32) -> !fir.type<_QMm2Tval{my_val:i32}>
+!CHECK:    fir.has_value %[[V1_INIT]] : !fir.type<_QMm2Tval{my_val:i32}>
+!CHECK:  }
diff --git a/flang/tools/bbc/bbc.cpp b/flang/tools/bbc/bbc.cpp
index 7efc460be86795..dafbcd856389a8 100644
--- a/flang/tools/bbc/bbc.cpp
+++ b/flang/tools/bbc/bbc.cpp
@@ -234,6 +234,11 @@ 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 "
@@ -381,6 +386,7 @@ 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;

llvmbot · 2025-01-20T12:45:04Z

@llvm/pr-subscribers-flang-driver

Author: Kiran Chandramohan (kiranchandramohan)

Changes

Reverts llvm/llvm-project#123330

Full diff: https://github.com/llvm/llvm-project/pull/123606.diff

9 Files Affected:

(modified) clang/include/clang/Driver/Options.td (+5)
(modified) clang/lib/Driver/ToolChains/Flang.cpp (+4-2)
(modified) flang/include/flang/Lower/LoweringOptions.def (+3)
(modified) flang/lib/Frontend/CompilerInvocation.cpp (+8)
(modified) flang/lib/Lower/ConvertVariable.cpp (+5-1)
(added) flang/test/Driver/fno-zero-init.f90 (+9)
(added) flang/test/Lower/zero_init.f90 (+20)
(added) flang/test/Lower/zero_init_default_init.f90 (+22)
(modified) flang/tools/bbc/bbc.cpp (+6)

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index d38dd2b4e3cf09..c4b9743597bb2e 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3505,6 +3505,11 @@ 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<
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 86ed25badfa2b7..9c1fd28a3a8a26 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -155,8 +155,10 @@ 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_ftime_report, options::OPT_ftime_report_EQ,
-                   options::OPT_funroll_loops, options::OPT_fno_unroll_loops});
+                   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});
 }
 
 void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
diff --git a/flang/include/flang/Lower/LoweringOptions.def b/flang/include/flang/Lower/LoweringOptions.def
index 5a6debfdffe030..396c91948be36b 100644
--- a/flang/include/flang/Lower/LoweringOptions.def
+++ b/flang/include/flang/Lower/LoweringOptions.def
@@ -44,5 +44,8 @@ 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
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 15b1e1e0a24881..3c6da4687f65d3 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -1377,6 +1377,14 @@ 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.
diff --git a/flang/lib/Lower/ConvertVariable.cpp b/flang/lib/Lower/ConvertVariable.cpp
index 9ee42d5cd88002..87236dc293ebbc 100644
--- a/flang/lib/Lower/ConvertVariable.cpp
+++ b/flang/lib/Lower/ConvertVariable.cpp
@@ -635,7 +635,11 @@ static fir::GlobalOp defineGlobal(Fortran::lower::AbstractConverter &converter,
       global.setLinkName(builder.createCommonLinkage());
     Fortran::lower::createGlobalInitialization(
         builder, global, [&](fir::FirOpBuilder &builder) {
-          mlir::Value initValue = builder.create<fir::ZeroOp>(loc, symTy);
+          mlir::Value initValue;
+          if (converter.getLoweringOptions().getInitGlobalZero())
+            initValue = builder.create<fir::ZeroOp>(loc, symTy);
+          else
+            initValue = builder.create<fir::UndefOp>(loc, symTy);
           builder.create<fir::HasValueOp>(loc, initValue);
         });
   }
diff --git a/flang/test/Driver/fno-zero-init.f90 b/flang/test/Driver/fno-zero-init.f90
new file mode 100644
index 00000000000000..2ffa10dd040d52
--- /dev/null
+++ b/flang/test/Driver/fno-zero-init.f90
@@ -0,0 +1,9 @@
+! Check that the driver passes through -f[no-]init-global-zero:
+! RUN: %flang -### -S -finit-global-zero %s -o - 2>&1 | FileCheck --check-prefix=CHECK-POS %s
+! RUN: %flang -### -S -fno-init-global-zero %s -o - 2>&1 | FileCheck --check-prefix=CHECK-NEG %s
+! Check that the compiler accepts -f[no-]init-global-zero:
+! RUN: %flang_fc1 -emit-hlfir -finit-global-zero %s -o -
+! RUN: %flang_fc1 -emit-hlfir -fno-init-global-zero %s -o -
+
+! CHECK-POS: "-fc1"{{.*}}"-finit-global-zero"
+! CHECK-NEG: "-fc1"{{.*}}"-fno-init-global-zero"
diff --git a/flang/test/Lower/zero_init.f90 b/flang/test/Lower/zero_init.f90
new file mode 100644
index 00000000000000..5ed6f2247de3b2
--- /dev/null
+++ b/flang/test/Lower/zero_init.f90
@@ -0,0 +1,20 @@
+! RUN: %flang_fc1 -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: %flang_fc1 -finit-global-zero -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: %flang_fc1 -fno-init-global-zero -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-NO-ZERO-INIT %s
+! RUN: bbc -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: bbc -finit-global-zero -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: bbc -finit-global-zero=false -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-NO-ZERO-INIT %s
+
+module m1
+  real :: x
+end module m1
+
+!CHECK-DEFAULT: fir.global @_QMm1Ex : f32 {
+!CHECK-DEFAULT:   %[[UNDEF:.*]] = fir.zero_bits f32
+!CHECK-DEFAULT:   fir.has_value %[[UNDEF]] : f32
+!CHECK-DEFAULT: }
+
+!CHECK-NO-ZERO-INIT: fir.global @_QMm1Ex : f32 {
+!CHECK-NO-ZERO-INIT:   %[[UNDEF:.*]] = fir.undefined f32
+!CHECK-NO-ZERO-INIT:   fir.has_value %[[UNDEF]] : f32
+!CHECK-NO-ZERO-INIT: }
diff --git a/flang/test/Lower/zero_init_default_init.f90 b/flang/test/Lower/zero_init_default_init.f90
new file mode 100644
index 00000000000000..e2d1f545e35a57
--- /dev/null
+++ b/flang/test/Lower/zero_init_default_init.f90
@@ -0,0 +1,22 @@
+! RUN: %flang_fc1 -emit-hlfir -o - %s | FileCheck %s
+! RUN: %flang_fc1 -finit-global-zero -emit-hlfir -o - %s | FileCheck %s
+! RUN: %flang_fc1 -fno-init-global-zero -emit-hlfir -o - %s | FileCheck %s
+! RUN: bbc -emit-hlfir -o - %s | FileCheck %s
+! RUN: bbc -finit-global-zero -emit-hlfir -o - %s | FileCheck %s
+! RUN: bbc -finit-global-zero=false -emit-hlfir -o - %s | FileCheck %s
+
+! Test that the flag does not affect globals with default init
+
+module m2
+  type val
+    integer :: my_val = 1
+  end type val
+  type(val) :: v1
+end module m2
+
+!CHECK:  fir.global @_QMm2Ev1 : !fir.type<_QMm2Tval{my_val:i32}> {
+!CHECK:    %[[V1:.*]] = fir.undefined !fir.type<_QMm2Tval{my_val:i32}>
+!CHECK:    %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK:    %[[V1_INIT:.*]] = fir.insert_value %[[V1]], %[[ONE]], ["my_val", !fir.type<_QMm2Tval{my_val:i32}>] : (!fir.type<_QMm2Tval{my_val:i32}>, i32) -> !fir.type<_QMm2Tval{my_val:i32}>
+!CHECK:    fir.has_value %[[V1_INIT]] : !fir.type<_QMm2Tval{my_val:i32}>
+!CHECK:  }
diff --git a/flang/tools/bbc/bbc.cpp b/flang/tools/bbc/bbc.cpp
index 7efc460be86795..dafbcd856389a8 100644
--- a/flang/tools/bbc/bbc.cpp
+++ b/flang/tools/bbc/bbc.cpp
@@ -234,6 +234,11 @@ 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 "
@@ -381,6 +386,7 @@ 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;

llvmbot · 2025-01-20T12:45:05Z

@llvm/pr-subscribers-flang-fir-hlfir

Author: Kiran Chandramohan (kiranchandramohan)

Changes

Reverts llvm/llvm-project#123330

Full diff: https://github.com/llvm/llvm-project/pull/123606.diff

9 Files Affected:

(modified) clang/include/clang/Driver/Options.td (+5)
(modified) clang/lib/Driver/ToolChains/Flang.cpp (+4-2)
(modified) flang/include/flang/Lower/LoweringOptions.def (+3)
(modified) flang/lib/Frontend/CompilerInvocation.cpp (+8)
(modified) flang/lib/Lower/ConvertVariable.cpp (+5-1)
(added) flang/test/Driver/fno-zero-init.f90 (+9)
(added) flang/test/Lower/zero_init.f90 (+20)
(added) flang/test/Lower/zero_init_default_init.f90 (+22)
(modified) flang/tools/bbc/bbc.cpp (+6)

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index d38dd2b4e3cf09..c4b9743597bb2e 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3505,6 +3505,11 @@ 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<
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 86ed25badfa2b7..9c1fd28a3a8a26 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -155,8 +155,10 @@ 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_ftime_report, options::OPT_ftime_report_EQ,
-                   options::OPT_funroll_loops, options::OPT_fno_unroll_loops});
+                   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});
 }
 
 void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
diff --git a/flang/include/flang/Lower/LoweringOptions.def b/flang/include/flang/Lower/LoweringOptions.def
index 5a6debfdffe030..396c91948be36b 100644
--- a/flang/include/flang/Lower/LoweringOptions.def
+++ b/flang/include/flang/Lower/LoweringOptions.def
@@ -44,5 +44,8 @@ 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
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 15b1e1e0a24881..3c6da4687f65d3 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -1377,6 +1377,14 @@ 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.
diff --git a/flang/lib/Lower/ConvertVariable.cpp b/flang/lib/Lower/ConvertVariable.cpp
index 9ee42d5cd88002..87236dc293ebbc 100644
--- a/flang/lib/Lower/ConvertVariable.cpp
+++ b/flang/lib/Lower/ConvertVariable.cpp
@@ -635,7 +635,11 @@ static fir::GlobalOp defineGlobal(Fortran::lower::AbstractConverter &converter,
       global.setLinkName(builder.createCommonLinkage());
     Fortran::lower::createGlobalInitialization(
         builder, global, [&](fir::FirOpBuilder &builder) {
-          mlir::Value initValue = builder.create<fir::ZeroOp>(loc, symTy);
+          mlir::Value initValue;
+          if (converter.getLoweringOptions().getInitGlobalZero())
+            initValue = builder.create<fir::ZeroOp>(loc, symTy);
+          else
+            initValue = builder.create<fir::UndefOp>(loc, symTy);
           builder.create<fir::HasValueOp>(loc, initValue);
         });
   }
diff --git a/flang/test/Driver/fno-zero-init.f90 b/flang/test/Driver/fno-zero-init.f90
new file mode 100644
index 00000000000000..2ffa10dd040d52
--- /dev/null
+++ b/flang/test/Driver/fno-zero-init.f90
@@ -0,0 +1,9 @@
+! Check that the driver passes through -f[no-]init-global-zero:
+! RUN: %flang -### -S -finit-global-zero %s -o - 2>&1 | FileCheck --check-prefix=CHECK-POS %s
+! RUN: %flang -### -S -fno-init-global-zero %s -o - 2>&1 | FileCheck --check-prefix=CHECK-NEG %s
+! Check that the compiler accepts -f[no-]init-global-zero:
+! RUN: %flang_fc1 -emit-hlfir -finit-global-zero %s -o -
+! RUN: %flang_fc1 -emit-hlfir -fno-init-global-zero %s -o -
+
+! CHECK-POS: "-fc1"{{.*}}"-finit-global-zero"
+! CHECK-NEG: "-fc1"{{.*}}"-fno-init-global-zero"
diff --git a/flang/test/Lower/zero_init.f90 b/flang/test/Lower/zero_init.f90
new file mode 100644
index 00000000000000..5ed6f2247de3b2
--- /dev/null
+++ b/flang/test/Lower/zero_init.f90
@@ -0,0 +1,20 @@
+! RUN: %flang_fc1 -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: %flang_fc1 -finit-global-zero -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: %flang_fc1 -fno-init-global-zero -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-NO-ZERO-INIT %s
+! RUN: bbc -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: bbc -finit-global-zero -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: bbc -finit-global-zero=false -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-NO-ZERO-INIT %s
+
+module m1
+  real :: x
+end module m1
+
+!CHECK-DEFAULT: fir.global @_QMm1Ex : f32 {
+!CHECK-DEFAULT:   %[[UNDEF:.*]] = fir.zero_bits f32
+!CHECK-DEFAULT:   fir.has_value %[[UNDEF]] : f32
+!CHECK-DEFAULT: }
+
+!CHECK-NO-ZERO-INIT: fir.global @_QMm1Ex : f32 {
+!CHECK-NO-ZERO-INIT:   %[[UNDEF:.*]] = fir.undefined f32
+!CHECK-NO-ZERO-INIT:   fir.has_value %[[UNDEF]] : f32
+!CHECK-NO-ZERO-INIT: }
diff --git a/flang/test/Lower/zero_init_default_init.f90 b/flang/test/Lower/zero_init_default_init.f90
new file mode 100644
index 00000000000000..e2d1f545e35a57
--- /dev/null
+++ b/flang/test/Lower/zero_init_default_init.f90
@@ -0,0 +1,22 @@
+! RUN: %flang_fc1 -emit-hlfir -o - %s | FileCheck %s
+! RUN: %flang_fc1 -finit-global-zero -emit-hlfir -o - %s | FileCheck %s
+! RUN: %flang_fc1 -fno-init-global-zero -emit-hlfir -o - %s | FileCheck %s
+! RUN: bbc -emit-hlfir -o - %s | FileCheck %s
+! RUN: bbc -finit-global-zero -emit-hlfir -o - %s | FileCheck %s
+! RUN: bbc -finit-global-zero=false -emit-hlfir -o - %s | FileCheck %s
+
+! Test that the flag does not affect globals with default init
+
+module m2
+  type val
+    integer :: my_val = 1
+  end type val
+  type(val) :: v1
+end module m2
+
+!CHECK:  fir.global @_QMm2Ev1 : !fir.type<_QMm2Tval{my_val:i32}> {
+!CHECK:    %[[V1:.*]] = fir.undefined !fir.type<_QMm2Tval{my_val:i32}>
+!CHECK:    %[[ONE:.*]] = arith.constant 1 : i32
+!CHECK:    %[[V1_INIT:.*]] = fir.insert_value %[[V1]], %[[ONE]], ["my_val", !fir.type<_QMm2Tval{my_val:i32}>] : (!fir.type<_QMm2Tval{my_val:i32}>, i32) -> !fir.type<_QMm2Tval{my_val:i32}>
+!CHECK:    fir.has_value %[[V1_INIT]] : !fir.type<_QMm2Tval{my_val:i32}>
+!CHECK:  }
diff --git a/flang/tools/bbc/bbc.cpp b/flang/tools/bbc/bbc.cpp
index 7efc460be86795..dafbcd856389a8 100644
--- a/flang/tools/bbc/bbc.cpp
+++ b/flang/tools/bbc/bbc.cpp
@@ -234,6 +234,11 @@ 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 "
@@ -381,6 +386,7 @@ 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;

Revert "Revert "Revert "Revert "[Flang][Driver] Add a flag to control…

ddb9cc5

… zero in…" This reverts commit 8a229f5.

llvmbot added clang Clang issues not falling into any other category clang:driver 'clang' and 'clang++' user-facing binaries. Not 'clang-cl' flang:driver flang Flang issues not falling into any other category flang:fir-hlfir labels Jan 20, 2025

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Reland "[Flang][Driver] Add a flag to control zero initialization" #123606

Reland "[Flang][Driver] Add a flag to control zero initialization" #123606

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llvmbot commented Jan 20, 2025 •

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llvmbot commented Jan 20, 2025

llvmbot commented Jan 20, 2025

Reland "[Flang][Driver] Add a flag to control zero initialization" #123606

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Reland "[Flang][Driver] Add a flag to control zero initialization" #123606

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