[flang-commits] [clang] [flang] [Flang][Driver] Add a flag to control zero initialization of global v… (PR #122144)
Kiran Chandramohan via flang-commits
flang-commits at lists.llvm.org
Wed Jan 8 10:09:02 PST 2025
https://github.com/kiranchandramohan updated https://github.com/llvm/llvm-project/pull/122144
>From 483501549b910d1e91dab05cce65793c44aaa6f6 Mon Sep 17 00:00:00 2001
From: Kiran Chandramohan <kiran.chandramohan at arm.com>
Date: Wed, 8 Jan 2025 17:26:24 +0000
Subject: [PATCH] [Flang][Driver] Add a flag to control zero initialization of
global variables
Patch adds a flag to control zero initialization of global variables
without default initialization. The default is to zero initialize.
---
clang/include/clang/Driver/Options.td | 3 +++
clang/lib/Driver/ToolChains/Flang.cpp | 1 +
flang/include/flang/Lower/LoweringOptions.def | 3 +++
flang/lib/Frontend/CompilerInvocation.cpp | 6 ++++++
flang/lib/Lower/ConvertVariable.cpp | 6 +++++-
flang/test/Driver/fno-zero-init.f90 | 5 +++++
flang/test/Lower/zero_init.f90 | 16 ++++++++++++++++
flang/test/Lower/zero_init_default_init.f90 | 18 ++++++++++++++++++
8 files changed, 57 insertions(+), 1 deletion(-)
create mode 100644 flang/test/Driver/fno-zero-init.f90
create mode 100644 flang/test/Lower/zero_init.f90
create mode 100644 flang/test/Lower/zero_init_default_init.f90
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 52823430919de4..e8d18cf78e985a 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3494,6 +3494,9 @@ 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]>;
+def fno_zero_init_global_without_init : Flag<["-"], "fno-zero-init-global-without-init">, Group<f_Group>,
+ Visibility<[FlangOption, FC1Option]>,
+ HelpText<"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 75b10e88371ae7..609f5315426977 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -153,6 +153,7 @@ void Flang::addCodegenOptions(const ArgList &Args,
Args.addAllArgs(CmdArgs, {options::OPT_flang_experimental_hlfir,
options::OPT_flang_deprecated_no_hlfir,
options::OPT_fno_ppc_native_vec_elem_order,
+ options::OPT_fno_zero_init_global_without_init,
options::OPT_fppc_native_vec_elem_order});
}
diff --git a/flang/include/flang/Lower/LoweringOptions.def b/flang/include/flang/Lower/LoweringOptions.def
index 5a6debfdffe030..acce21f5faab8b 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(ZeroInitGlobalsWithoutInit, unsigned, 1, 1)
#undef LOWERINGOPT
#undef ENUM_LOWERINGOPT
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 340efb1c63a5e5..fa91a0e2642bc8 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -1373,6 +1373,12 @@ bool CompilerInvocation::createFromArgs(
invoc.loweringOpts.setNoPPCNativeVecElemOrder(true);
}
+ // -fno-zero-init-global-without-init
+ if (args.hasArg(
+ clang::driver::options::OPT_fno_zero_init_global_without_init)) {
+ invoc.loweringOpts.setZeroInitGlobalsWithoutInit(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..db8a57d416274c 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().getZeroInitGlobalsWithoutInit())
+ 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..faa757b32a8dab
--- /dev/null
+++ b/flang/test/Driver/fno-zero-init.f90
@@ -0,0 +1,5 @@
+! Check that the driver passes through -fno-zero-init-global-without-init:
+! RUN: %flang -### -S -fno-zero-init-global-without-init %s -o - 2>&1 | FileCheck %s
+! Check that the compiler accepts -fno-zero-init-global-without-init:
+! RUN: %flang_fc1 -emit-hlfir -fno-zero-init-global-without-init %s -o -
+! CHECK: "-fc1"{{.*}}"-fno-zero-init-global-without-init"
diff --git a/flang/test/Lower/zero_init.f90 b/flang/test/Lower/zero_init.f90
new file mode 100644
index 00000000000000..76201eb0f0cbd0
--- /dev/null
+++ b/flang/test/Lower/zero_init.f90
@@ -0,0 +1,16 @@
+! RUN: %flang_fc1 -emit-hlfir -o - %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+! RUN: %flang_fc1 -fno-zero-init-global-without-init -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..ac6faf37e8d1bf
--- /dev/null
+++ b/flang/test/Lower/zero_init_default_init.f90
@@ -0,0 +1,18 @@
+! RUN: %flang_fc1 -emit-hlfir -o - %s | FileCheck %s
+! RUN: %flang_fc1 -fno-zero-init-global-without-init -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: }
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