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[clang][X86] Support __attribute__((model("small"/"large")))
Following up #72078, on x86-64 this allows a global to be considered small or large regardless of the code model. For example, x86-64's medium code model by default classifies globals as small or large depending on their size relative to -mlarge-data-threshold.
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5 files changed

+61
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‎clang/docs/ReleaseNotes.rst‎

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@@ -657,6 +657,11 @@ Attribute Changes in Clang
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- Clang now disallows the use of attributes after the namespace name. (#GH121407)
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- Clang now allows ``__attribute__((model("small")))`` and
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``__attribute__((model("large")))`` on non-TLS globals in x86-64 compilations.
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This forces the global to be considered small or large in regards to the
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x86-64 code model, regardless of the code model specified for the compilation.
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Improvements to Clang's diagnostics
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-----------------------------------
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‎clang/include/clang/Basic/Attr.td‎

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@@ -462,6 +462,7 @@ def TargetMSP430 : TargetArch<["msp430"]>;
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def TargetM68k : TargetArch<["m68k"]>;
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def TargetRISCV : TargetArch<["riscv32", "riscv64"]>;
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def TargetX86 : TargetArch<["x86"]>;
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def TargetX86_64 : TargetArch<["x86_64"]>;
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def TargetAnyX86 : TargetArch<["x86", "x86_64"]>;
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def TargetWebAssembly : TargetArch<["wasm32", "wasm64"]>;
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def TargetNVPTX : TargetArch<["nvptx", "nvptx64"]>;
@@ -3117,11 +3118,15 @@ def PragmaClangTextSection : InheritableAttr {
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let Documentation = [InternalOnly];
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}
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def CodeModel : InheritableAttr, TargetSpecificAttr<TargetLoongArch> {
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def CodeModel : InheritableAttr,
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TargetSpecificAttr<TargetArch<!listconcat(
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TargetLoongArch.Arches, TargetX86_64.Arches)>> {
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let Spellings = [GCC<"model">];
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let Args = [EnumArgument<"Model", "llvm::CodeModel::Model", /*is_string=*/1,
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["normal", "medium", "extreme"], ["Small", "Medium", "Large"],
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/*opt=*/0, /*fake=*/0, /*isExternalType=*/1, /*isCovered=*/0>];
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let Args = [EnumArgument<
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"Model", "llvm::CodeModel::Model",
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/*is_string=*/1, ["small", "normal", "medium", "large", "extreme"],
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["Small", "Small", "Medium", "Large", "Large"],
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/*opt=*/0, /*fake=*/0, /*isExternalType=*/1, /*isCovered=*/0>];
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let Subjects = SubjectList<[NonTLSGlobalVar], ErrorDiag>;
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let Documentation = [CodeModelDocs];
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}

‎clang/lib/Sema/SemaDeclAttr.cpp‎

Lines changed: 10 additions & 1 deletion
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@@ -64,6 +64,7 @@
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/MC/MCSectionMachO.h"
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#include "llvm/Support/Error.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/TargetParser/Triple.h"
@@ -2949,6 +2950,13 @@ static void handleSectionAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
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}
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}
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static bool isValidCodeModelAttr(Sema &S, StringRef Str) {
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bool IsX8664Target =
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S.Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86_64;
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bool IsX8664Spelling = Str == "small" || Str == "large";
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return IsX8664Target == IsX8664Spelling;
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}
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static void handleCodeModelAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
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StringRef Str;
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SourceLocation LiteralLoc;
@@ -2957,7 +2965,8 @@ static void handleCodeModelAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
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return;
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llvm::CodeModel::Model CM;
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if (!CodeModelAttr::ConvertStrToModel(Str, CM)) {
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if (!CodeModelAttr::ConvertStrToModel(Str, CM) ||
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!isValidCodeModelAttr(S, Str)) {
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S.Diag(LiteralLoc, diag::err_attr_codemodel_arg) << Str;
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return;
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}

‎clang/test/CodeGen/X86/codemodel.cpp‎

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@@ -0,0 +1,27 @@
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// RUN: %clang_cc1 -emit-llvm -triple x86_64-unknown-unknown %s -o - | FileCheck %s
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// CHECK: @_ZL2v1 ={{.*}} global i32 0, code_model "small"
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static int v1 __attribute__((model("small")));
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void use1() {
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v1 = 1;
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}
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// CHECK: @v2 ={{.*}} global float 0.000000e+00, code_model "large"
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float v2 __attribute__((model("large")));
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// CHECK: @_ZL2v3IiE ={{.*}} global i32 0, code_model "small"
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template <typename T>
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static T v3 __attribute__((model("small")));
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void use2() {
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v3<int> = 1;
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}
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struct S {
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double d;
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};
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typedef void (*F)();
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// CHECK: @v4 ={{.*}} global ptr null, code_model "large"
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F v4 __attribute__((model("large")));

‎clang/test/Sema/attr-model.cpp‎

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@@ -5,7 +5,7 @@
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// RUN: %clang_cc1 -triple riscv64 -verify=expected,riscv64 -fsyntax-only %s
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// RUN: %clang_cc1 -triple x86_64 -verify=expected,x86_64 -fsyntax-only %s
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#if defined(__loongarch__) && !__has_attribute(model)
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#if (defined(__loongarch__) || defined(__x86_64__)) && !__has_attribute(model)
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#error "Should support model attribute"
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#endif
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@@ -14,51 +14,49 @@ int a __attribute((model("tiny"))); // aarch64-warning {{unknown attribute 'm
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// mips64-warning {{unknown attribute 'model' ignored}} \
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// powerpc64-warning {{unknown attribute 'model' ignored}} \
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// riscv64-warning {{unknown attribute 'model' ignored}} \
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// x86_64-warning {{unknown attribute 'model' ignored}}
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// x86_64-error {{code model 'tiny' is not supported on this target}}
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int b __attribute((model("small"))); // aarch64-warning {{unknown attribute 'model' ignored}} \
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// loongarch64-error {{code model 'small' is not supported on this target}} \
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// mips64-warning {{unknown attribute 'model' ignored}} \
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// powerpc64-warning {{unknown attribute 'model' ignored}} \
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// riscv64-warning {{unknown attribute 'model' ignored}} \
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// x86_64-warning {{unknown attribute 'model' ignored}}
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// riscv64-warning {{unknown attribute 'model' ignored}}
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int c __attribute((model("normal"))); // aarch64-warning {{unknown attribute 'model' ignored}} \
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// mips64-warning {{unknown attribute 'model' ignored}} \
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// powerpc64-warning {{unknown attribute 'model' ignored}} \
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// riscv64-warning {{unknown attribute 'model' ignored}} \
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// x86_64-warning {{unknown attribute 'model' ignored}}
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// x86_64-error {{code model 'normal' is not supported on this target}}
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int d __attribute((model("kernel"))); // aarch64-warning {{unknown attribute 'model' ignored}} \
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// loongarch64-error {{code model 'kernel' is not supported on this target}} \
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// mips64-warning {{unknown attribute 'model' ignored}} \
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// powerpc64-warning {{unknown attribute 'model' ignored}} \
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// riscv64-warning {{unknown attribute 'model' ignored}} \
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// x86_64-warning {{unknown attribute 'model' ignored}}
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// x86_64-error {{code model 'kernel' is not supported on this target}}
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int e __attribute((model("medium"))); // aarch64-warning {{unknown attribute 'model' ignored}} \
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// mips64-warning {{unknown attribute 'model' ignored}} \
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// powerpc64-warning {{unknown attribute 'model' ignored}} \
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// riscv64-warning {{unknown attribute 'model' ignored}} \
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// x86_64-warning {{unknown attribute 'model' ignored}}
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// x86_64-error {{code model 'medium' is not supported on this target}}
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int f __attribute((model("large"))); // aarch64-warning {{unknown attribute 'model' ignored}} \
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// loongarch64-error {{code model 'large' is not supported on this target}} \
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// mips64-warning {{unknown attribute 'model' ignored}} \
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// powerpc64-warning {{unknown attribute 'model' ignored}} \
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// riscv64-warning {{unknown attribute 'model' ignored}} \
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// x86_64-warning {{unknown attribute 'model' ignored}}
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// riscv64-warning {{unknown attribute 'model' ignored}}
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int g __attribute((model("extreme"))); // aarch64-warning {{unknown attribute 'model' ignored}} \
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// mips64-warning {{unknown attribute 'model' ignored}} \
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// powerpc64-warning {{unknown attribute 'model' ignored}} \
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// riscv64-warning {{unknown attribute 'model' ignored}} \
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// x86_64-warning {{unknown attribute 'model' ignored}}
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// x86_64-error {{code model 'extreme' is not supported on this target}}
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void __attribute((model("extreme"))) h() {} // aarch64-warning {{unknown attribute 'model' ignored}} \
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// loongarch64-error {{'model' attribute only applies to non-TLS global variables}} \
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// mips64-warning {{unknown attribute 'model' ignored}} \
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// powerpc64-warning {{unknown attribute 'model' ignored}} \
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// riscv64-warning {{unknown attribute 'model' ignored}} \
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// x86_64-warning {{unknown attribute 'model' ignored}}
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// x86_64-error {{'model' attribute only applies to non-TLS global variables}}
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thread_local int i __attribute((model("extreme"))); // aarch64-warning {{unknown attribute 'model' ignored}} \
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// loongarch64-error {{'model' attribute only applies to non-TLS global variables}} \
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// mips64-warning {{unknown attribute 'model' ignored}} \
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// powerpc64-warning {{unknown attribute 'model' ignored}} \
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// riscv64-warning {{unknown attribute 'model' ignored}} \
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// x86_64-warning {{unknown attribute 'model' ignored}}
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// x86_64-error {{'model' attribute only applies to non-TLS global variables}}

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