eandrews updated this revision to Diff 161307.
eandrews edited the summary of this revision.
eandrews added a comment.
This patch fell through the cracks earlier. I apologize. Based on Reid's and
Erich's feedback, I am now adding the variable to @llvm.used. Additionally I
modified the if statements to ensure only static variables are considered.
I also compared the IR when using the option -fkeep-static-consts while
compiling the program, vs adding __attribute__((used)) to individual variables
inside the program. The generated IR had no difference. I assume this means all
required information to prevent the variable from being removed in later stages
are now being emitted?
https://reviews.llvm.org/D40925
Files:
include/clang/Basic/LangOptions.def
include/clang/Driver/Options.td
lib/AST/ASTContext.cpp
lib/CodeGen/CodeGenModule.cpp
lib/Driver/ToolChains/Clang.cpp
lib/Frontend/CompilerInvocation.cpp
test/CodeGen/keep-static-consts.cpp
Index: test/CodeGen/keep-static-consts.cpp
===================================================================
--- /dev/null
+++ test/CodeGen/keep-static-consts.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fkeep-static-consts -emit-llvm %s -o -
-triple=x86_64-unknown-linux-gnu | FileCheck %s
+
+// CHECK: @_ZL7srcvers = internal constant [4 x i8] c"xyz\00", align 1
+// CHECK: @llvm.used = appending global [1 x i8*] [i8* getelementptr inbounds
([4 x i8], [4 x i8]* @_ZL7srcvers, i32 0, i32 0)], section "llvm.metadata"
+static const char srcvers[] = "xyz";
+extern const int b = 1;
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -2485,6 +2485,7 @@
Opts.HalfArgsAndReturns = Args.hasArg(OPT_fallow_half_arguments_and_returns)
| Opts.NativeHalfArgsAndReturns;
Opts.GNUAsm = !Args.hasArg(OPT_fno_gnu_inline_asm);
+ Opts.KeepStaticConsts = Args.hasArg(OPT_fkeep_static_consts);
// __declspec is enabled by default for the PS4 by the driver, and also
// enabled for Microsoft Extensions or Borland Extensions, here.
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -3996,6 +3996,7 @@
Args.AddLastArg(CmdArgs, options::OPT_fno_operator_names);
Args.AddLastArg(CmdArgs, options::OPT_femulated_tls,
options::OPT_fno_emulated_tls);
+ Args.AddLastArg(CmdArgs, options::OPT_fkeep_static_consts);
// AltiVec-like language extensions aren't relevant for assembling.
if (!isa<PreprocessJobAction>(JA) || Output.getType() != types::TY_PP_Asm)
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -1350,6 +1350,12 @@
if (D && D->hasAttr<UsedAttr>())
addUsedGlobal(GV);
+
+ if (LangOpts.KeepStaticConsts && D && isa<VarDecl>(D)) {
+ const auto *VD = cast<VarDecl>(D);
+ if (VD->getType().isConstQualified() && VD->getStorageClass() == SC_Static)
+ addUsedGlobal(GV);
+ }
}
bool CodeGenModule::GetCPUAndFeaturesAttributes(const Decl *D,
Index: lib/AST/ASTContext.cpp
===================================================================
--- lib/AST/ASTContext.cpp
+++ lib/AST/ASTContext.cpp
@@ -9741,6 +9741,14 @@
if (D->hasAttr<AliasAttr>() || D->hasAttr<UsedAttr>())
return true;
+ // Emit static constants even if they are not used if KeepStaticConsts is
set.
+ if (LangOpts.KeepStaticConsts) {
+ const auto *VD = dyn_cast<VarDecl>(D);
+ if (VD && VD->getType().isConstQualified() &&
+ VD->getStorageClass() == SC_Static)
+ return true;
+ }
+
if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
// Forward declarations aren't required.
if (!FD->doesThisDeclarationHaveABody())
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -893,7 +893,8 @@
def fno_force_enable_int128 : Flag<["-"], "fno-force-enable-int128">,
Group<f_Group>, Flags<[CC1Option]>,
HelpText<"Disable support for int128_t type">;
-
+def fkeep_static_consts : Flag<["-"], "fkeep-static-consts">, Group<f_Group>,
Flags<[CC1Option]>,
+ HelpText<"Keep static const variables even if unused">;
def ffixed_point : Flag<["-"], "ffixed-point">, Group<f_Group>,
Flags<[CC1Option]>, HelpText<"Enable fixed point types">;
def fno_fixed_point : Flag<["-"], "fno-fixed-point">, Group<f_Group>,
Index: include/clang/Basic/LangOptions.def
===================================================================
--- include/clang/Basic/LangOptions.def
+++ include/clang/Basic/LangOptions.def
@@ -308,6 +308,8 @@
LANGOPT(PaddingOnUnsignedFixedPoint, 1, 0,
"unsigned fixed point types having one extra padding bit")
+BENIGN_LANGOPT(KeepStaticConsts , 1, 0, "keep static const variables even
if unused")
+
#undef LANGOPT
#undef COMPATIBLE_LANGOPT
#undef BENIGN_LANGOPT
Index: test/CodeGen/keep-static-consts.cpp
===================================================================
--- /dev/null
+++ test/CodeGen/keep-static-consts.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fkeep-static-consts -emit-llvm %s -o - -triple=x86_64-unknown-linux-gnu | FileCheck %s
+
+// CHECK: @_ZL7srcvers = internal constant [4 x i8] c"xyz\00", align 1
+// CHECK: @llvm.used = appending global [1 x i8*] [i8* getelementptr inbounds ([4 x i8], [4 x i8]* @_ZL7srcvers, i32 0, i32 0)], section "llvm.metadata"
+static const char srcvers[] = "xyz";
+extern const int b = 1;
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -2485,6 +2485,7 @@
Opts.HalfArgsAndReturns = Args.hasArg(OPT_fallow_half_arguments_and_returns)
| Opts.NativeHalfArgsAndReturns;
Opts.GNUAsm = !Args.hasArg(OPT_fno_gnu_inline_asm);
+ Opts.KeepStaticConsts = Args.hasArg(OPT_fkeep_static_consts);
// __declspec is enabled by default for the PS4 by the driver, and also
// enabled for Microsoft Extensions or Borland Extensions, here.
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -3996,6 +3996,7 @@
Args.AddLastArg(CmdArgs, options::OPT_fno_operator_names);
Args.AddLastArg(CmdArgs, options::OPT_femulated_tls,
options::OPT_fno_emulated_tls);
+ Args.AddLastArg(CmdArgs, options::OPT_fkeep_static_consts);
// AltiVec-like language extensions aren't relevant for assembling.
if (!isa<PreprocessJobAction>(JA) || Output.getType() != types::TY_PP_Asm)
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -1350,6 +1350,12 @@
if (D && D->hasAttr<UsedAttr>())
addUsedGlobal(GV);
+
+ if (LangOpts.KeepStaticConsts && D && isa<VarDecl>(D)) {
+ const auto *VD = cast<VarDecl>(D);
+ if (VD->getType().isConstQualified() && VD->getStorageClass() == SC_Static)
+ addUsedGlobal(GV);
+ }
}
bool CodeGenModule::GetCPUAndFeaturesAttributes(const Decl *D,
Index: lib/AST/ASTContext.cpp
===================================================================
--- lib/AST/ASTContext.cpp
+++ lib/AST/ASTContext.cpp
@@ -9741,6 +9741,14 @@
if (D->hasAttr<AliasAttr>() || D->hasAttr<UsedAttr>())
return true;
+ // Emit static constants even if they are not used if KeepStaticConsts is set.
+ if (LangOpts.KeepStaticConsts) {
+ const auto *VD = dyn_cast<VarDecl>(D);
+ if (VD && VD->getType().isConstQualified() &&
+ VD->getStorageClass() == SC_Static)
+ return true;
+ }
+
if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
// Forward declarations aren't required.
if (!FD->doesThisDeclarationHaveABody())
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -893,7 +893,8 @@
def fno_force_enable_int128 : Flag<["-"], "fno-force-enable-int128">,
Group<f_Group>, Flags<[CC1Option]>,
HelpText<"Disable support for int128_t type">;
-
+def fkeep_static_consts : Flag<["-"], "fkeep-static-consts">, Group<f_Group>, Flags<[CC1Option]>,
+ HelpText<"Keep static const variables even if unused">;
def ffixed_point : Flag<["-"], "ffixed-point">, Group<f_Group>,
Flags<[CC1Option]>, HelpText<"Enable fixed point types">;
def fno_fixed_point : Flag<["-"], "fno-fixed-point">, Group<f_Group>,
Index: include/clang/Basic/LangOptions.def
===================================================================
--- include/clang/Basic/LangOptions.def
+++ include/clang/Basic/LangOptions.def
@@ -308,6 +308,8 @@
LANGOPT(PaddingOnUnsignedFixedPoint, 1, 0,
"unsigned fixed point types having one extra padding bit")
+BENIGN_LANGOPT(KeepStaticConsts , 1, 0, "keep static const variables even if unused")
+
#undef LANGOPT
#undef COMPATIBLE_LANGOPT
#undef BENIGN_LANGOPT
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
