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Yassine Missoumsivadeilra
Yassine Missoum
authored and
sivadeilra
committed
Implementation of flag /cbstring
1 parent 3e8908c commit 12f7ba1

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8 files changed

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8 files changed

+153
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‎clang/include/clang/Basic/CodeGenOptions.def‎

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Original file line numberDiff line numberDiff line change
@@ -148,6 +148,7 @@ CODEGENOPT(HotPatch, 1, 0, Benign) ///< Supports the Microsoft /HOTPATCH flag an
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///< generates a 'patchable-function' attribute.
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150150
CODEGENOPT(TlsGuards , 1, 1, Benign) ///< Controls emission of tls guards via -fms-tls-guards
151+
CODEGENOPT(CBString, 1, 0, Benign) ///< Place string literals in .text section (Microsoft /cbstring flag)
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CODEGENOPT(JMCInstrument, 1, 0, Benign) ///< Set when -fjmc is enabled.
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CODEGENOPT(InstrumentForProfiling , 1, 0, Benign) ///< Set when -pg is enabled.
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CODEGENOPT(CallFEntry , 1, 0, Benign) ///< Set when -mfentry is enabled.

‎clang/include/clang/Driver/Options.td‎

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Original file line numberDiff line numberDiff line change
@@ -3878,6 +3878,10 @@ def fms_hotpatch : Flag<["-"], "fms-hotpatch">, Group<f_Group>,
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Visibility<[ClangOption, CC1Option, CLOption]>,
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HelpText<"Ensure that all functions can be hotpatched at runtime">,
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MarshallingInfoFlag<CodeGenOpts<"HotPatch">>;
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def fms_cbstring : Flag<["-"], "fms-cbstring">, Group<f_Group>,
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Visibility<[ClangOption, CC1Option, CLOption]>,
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HelpText<"Place string literals in .text section">,
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MarshallingInfoFlag<CodeGenOpts<"CBString">>;
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// See llvm/lib/CodeGen/WindowsSecureHotPatching.cpp
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def fms_secure_hotpatch_functions_file
@@ -9062,6 +9066,8 @@ def _SLASH_QIntel_jcc_erratum : CLFlag<"QIntel-jcc-erratum">,
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Alias<mbranches_within_32B_boundaries>;
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def _SLASH_arm64EC : CLFlag<"arm64EC">,
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HelpText<"Set build target to arm64ec">;
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def _SLASH_cbstring : CLFlag<"cbstring">, Alias<fms_cbstring>,
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HelpText<"Place string literals in .text section">;
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def : CLFlag<"Qgather-">, Alias<mno_gather>,
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HelpText<"Disable generation of gather instructions in auto-vectorization(x86 only)">;
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def : CLFlag<"Qscatter-">, Alias<mno_scatter>,

‎clang/lib/CodeGen/CGExpr.cpp‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3416,7 +3416,7 @@ LValue CodeGenFunction::EmitUnaryOpLValue(const UnaryOperator *E) {
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}
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LValue CodeGenFunction::EmitStringLiteralLValue(const StringLiteral *E) {
3419-
return MakeAddrLValue(CGM.GetAddrOfConstantStringFromLiteral(E),
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return MakeAddrLValue(CGM.GetAddrOfConstantStringFromLiteral(E, ".str", CurFn),
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E->getType(), AlignmentSource::Decl);
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}
34223422

@@ -3448,7 +3448,7 @@ LValue CodeGenFunction::EmitPredefinedLValue(const PredefinedExpr *E) {
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return MakeAddrLValue(C, E->getType(), AlignmentSource::Decl);
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}
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}
3451-
auto C = CGM.GetAddrOfConstantStringFromLiteral(SL, GVName);
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auto C = CGM.GetAddrOfConstantStringFromLiteral(SL, GVName, CurFn);
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return MakeAddrLValue(C, E->getType(), AlignmentSource::Decl);
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}
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‎clang/lib/CodeGen/CodeGenModule.cpp‎

Lines changed: 20 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -6819,7 +6819,7 @@ CodeGenModule::GetConstantArrayFromStringLiteral(const StringLiteral *E) {
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static llvm::GlobalVariable *
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GenerateStringLiteral(llvm::Constant *C, llvm::GlobalValue::LinkageTypes LT,
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CodeGenModule &CGM, StringRef GlobalName,
6822-
CharUnits Alignment) {
6822+
CharUnits Alignment, llvm::Function *CurrentFunc = nullptr) {
68236823
unsigned AddrSpace = CGM.getContext().getTargetAddressSpace(
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CGM.GetGlobalConstantAddressSpace());
68256825

@@ -6836,14 +6836,31 @@ GenerateStringLiteral(llvm::Constant *C, llvm::GlobalValue::LinkageTypes LT,
68366836
}
68376837
CGM.setDSOLocal(GV);
68386838

6839+
// If /cbstring flag is enabled, place function-local string literals in code
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// sections following MSVC behavior:
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// - Function strings without custom section → .text$s
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// - Function strings with custom section → <section>$s
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// - Global strings → default section (like MSVC's CONST)
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if (CGM.getCodeGenOpts().CBString && CurrentFunc) {
6845+
if (CurrentFunc->hasSection()) {
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// Function has a custom section, append $s to it
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GV->setSection((Twine(CurrentFunc->getSection()) + "$s").str());
6848+
} else {
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// Function has no custom section, use .text$s
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GV->setSection(".text$s");
6851+
}
6852+
}
6853+
// Note: Global strings (CurrentFunc == nullptr) keep default section behavior
6854+
68396855
return GV;
68406856
}
68416857

68426858
/// GetAddrOfConstantStringFromLiteral - Return a pointer to a
68436859
/// constant array for the given string literal.
68446860
ConstantAddress
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CodeGenModule::GetAddrOfConstantStringFromLiteral(const StringLiteral *S,
6846-
StringRef Name) {
6862+
StringRef Name,
6863+
llvm::Function *CurrentFunc) {
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CharUnits Alignment =
68486865
getContext().getAlignOfGlobalVarInChars(S->getType(), /*VD=*/nullptr);
68496866

@@ -6877,7 +6894,7 @@ CodeGenModule::GetAddrOfConstantStringFromLiteral(const StringLiteral *S,
68776894
GlobalVariableName = Name;
68786895
}
68796896

6880-
auto GV = GenerateStringLiteral(C, LT, *this, GlobalVariableName, Alignment);
6897+
auto GV = GenerateStringLiteral(C, LT, *this, GlobalVariableName, Alignment, CurrentFunc);
68816898

68826899
CGDebugInfo *DI = getModuleDebugInfo();
68836900
if (DI && getCodeGenOpts().hasReducedDebugInfo())

‎clang/lib/CodeGen/CodeGenModule.h‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1174,7 +1174,8 @@ class CodeGenModule : public CodeGenTypeCache {
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/// Return a pointer to a constant array for the given string literal.
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ConstantAddress
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GetAddrOfConstantStringFromLiteral(const StringLiteral *S,
1177-
StringRef Name = ".str");
1177+
StringRef Name = ".str",
1178+
llvm::Function *CurrentFunc = nullptr);
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/// Return a pointer to a constant array for the given ObjCEncodeExpr node.
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ConstantAddress

‎clang/lib/Driver/ToolChains/Clang.cpp‎

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Original file line numberDiff line numberDiff line change
@@ -6782,6 +6782,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
67826782
}
67836783

67846784
Args.AddLastArg(CmdArgs, options::OPT_fms_hotpatch);
6785+
Args.AddLastArg(CmdArgs, options::OPT_fms_cbstring);
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67866787
if (Args.hasArg(options::OPT_fms_secure_hotpatch_functions_file))
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Args.AddLastArg(CmdArgs, options::OPT_fms_secure_hotpatch_functions_file);

‎clang/test/CodeGen/ms-cbstring.c‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,117 @@
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// Comprehensive test for -fms-cbstring flag functionality
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// RUN: %clang_cc1 -emit-llvm -fms-cbstring -fms-extensions %s -o - | FileCheck --check-prefixes=CBSTRING,CHECK %s
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// RUN: %clang_cc1 -emit-llvm -fms-extensions %s -o - | FileCheck --check-prefixes=NORMAL,CHECK %s
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// Function declarations to avoid needing system headers
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int printf(const char* format, ...);
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// Helper function declaration
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int uses_string(const char*);
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// Global scope strings
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const char *global_str = "global_test";
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static const char *static_global_str = "static_global_test";
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// String arrays
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const char *array[] = {"array_element1", "array_element2"};
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18+
// Function in default text section
19+
void test_function() {
20+
const char *local_str = "local_test";
21+
static const char *static_local_str = "static_local_test";
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23+
// Concatenated strings
24+
const char *concat = "concat_" "string_test";
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26+
// Use strings to prevent optimization
27+
printf("%s %s %s\n", local_str, static_local_str, concat);
28+
}
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30+
// Function with custom code segment
31+
void __declspec(code_seg("other_seg")) in_other_seg(void)
32+
{
33+
uses_string("test_in_other_seg");
34+
}
35+
36+
int main() {
37+
const char *main_str = "main_function_test";
38+
static const char *static_main_str = "static_main_test";
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40+
// Use all strings to ensure they appear in IR
41+
printf("%s %s %s %s %s\n", global_str, static_global_str, array[0], array[1], main_str);
42+
printf("%s\n", static_main_str);
43+
test_function();
44+
in_other_seg();
45+
46+
return 0;
47+
}
48+
49+
// Check string constants in order they appear in IR:
50+
// Note: With -fms-cbstring, function strings get section attributes but remain comdats for proper deduplication
51+
// Note: Global strings keep default section behavior (like MSVC's CONST segment)
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53+
// Global strings - should keep default section behavior (not go to .text$s)
54+
// NORMAL: constant {{.*}} c"global_test\00"{{.*}}comdat
55+
// CBSTRING: constant {{.*}} c"global_test\00"
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// CBSTRING-NOT: section
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// CBSTRING-SAME: comdat
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59+
// Array elements (global scope) - should keep default section behavior
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// NORMAL: constant {{.*}} c"array_element1\00"{{.*}}comdat
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// CBSTRING: constant {{.*}} c"array_element1\00"
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// CBSTRING-NOT: section
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// CBSTRING-SAME: comdat
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// NORMAL: constant {{.*}} c"array_element2\00"{{.*}}comdat
65+
// CBSTRING: constant {{.*}} c"array_element2\00"
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// CBSTRING-NOT: section
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// CBSTRING-SAME: comdat
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69+
// Function local strings go to .text$s
70+
// CHECK: constant {{.*}} c"local_test\00"
71+
// CBSTRING-SAME: section ".text$s"
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// NORMAL-NOT: section
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// CHECK-SAME: comdat
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75+
// Static local strings keep default section behavior (like MSVC)
76+
// CHECK: constant {{.*}} c"static_local_test\00"
77+
// CBSTRING-NOT: section
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// NORMAL-NOT: section
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// CHECK-SAME: comdat
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81+
// Concatenated strings in functions go to .text$s
82+
// CHECK: constant {{.*}} c"concat_string_test\00"
83+
// CBSTRING-SAME: section ".text$s"
84+
// NORMAL-NOT: section
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// CHECK-SAME: comdat
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87+
// Printf format strings also go to .text$s when used in functions
88+
// CBSTRING: section ".text$s"{{.*}}comdat
89+
90+
// Strings in function with custom code segment go to other_seg$s
91+
// CHECK: constant {{.*}} c"test_in_other_seg\00"
92+
// CBSTRING-SAME: section "other_seg$s"
93+
// NORMAL-NOT: section
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// CHECK-SAME: comdat
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96+
// Main function strings go to .text$s
97+
// CHECK: constant {{.*}} c"main_function_test\00"
98+
// CBSTRING-SAME: section ".text$s"
99+
// NORMAL-NOT: section
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// CHECK-SAME: comdat
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102+
// Static main function strings keep default section behavior
103+
// NORMAL: constant {{.*}} c"static_main_test\00"{{.*}}comdat
104+
// CBSTRING: constant {{.*}} c"static_main_test\00"
105+
// CBSTRING-NOT: section
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// CBSTRING-SAME: comdat
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108+
// Static global strings keep default section behavior
109+
// NORMAL: constant {{.*}} c"static_global_test\00"{{.*}}comdat
110+
// CBSTRING: constant {{.*}} c"static_global_test\00"
111+
// CBSTRING-NOT: section
112+
// CBSTRING-SAME: comdat
113+
114+
// Check that functions are defined
115+
// CHECK: define dso_local void @test_function()
116+
// CHECK: define dso_local void @in_other_seg()
117+
// CHECK: define dso_local i32 @main()

‎clang/test/Driver/cl-options.c‎

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Original file line numberDiff line numberDiff line change
@@ -198,6 +198,10 @@
198198
// Ox: -O3
199199
// Ox: -mframe-pointer=none
200200

201+
// RUN: %clang_cl /cbstring --target=i686-pc-windows-msvc -### -- %s 2>&1 | FileCheck -check-prefix=cbstring %s
202+
// RUN: %clang_cl /cbstring --target=x86_64-pc-windows-msvc -### -- %s 2>&1 | FileCheck -check-prefix=cbstring %s
203+
// cbstring: -fms-cbstring
204+
201205
// RUN: %clang_cl --target=i686-pc-win32 /O2sy- -### -- %s 2>&1 | FileCheck -check-prefix=PR24003 %s
202206
// PR24003: -Os
203207
// PR24003: -mframe-pointer=all

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