r359067 - [Builtins] Implement __builtin_is_constant_evaluated for use in C++2a
Eric Fiselier via cfe-commits
cfe-commits at lists.llvm.org
Wed Apr 24 19:28:16 PDT 2019
Do I just edit the HTML file directly?
Or is it generated by something?
On Wed, Apr 24, 2019 at 3:35 PM Richard Smith <richard at metafoo.co.uk> wrote:
> Thanks! Can you update cxx_status.html to mark P0595R2 as done?
>
> On Tue, 23 Apr 2019 at 19:21, Eric Fiselier via cfe-commits
> <cfe-commits at lists.llvm.org> wrote:
> >
> > Author: ericwf
> > Date: Tue Apr 23 19:23:30 2019
> > New Revision: 359067
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=359067&view=rev
> > Log:
> > [Builtins] Implement __builtin_is_constant_evaluated for use in C++2a
> >
> > Summary:
> > This patch implements `__builtin_is_constant_evaluated` as specifier by
> [P0595R2](https://wg21.link/p0595r2). It is built on the back of Bill
> Wendling's work for `__builtin_constant_p()`.
> >
> > More tests to come, but early feedback is appreciated.
> >
> > I plan to implement warnings for common mis-usages like those belowe in
> a following patch:
> > ```
> > void foo(int x) {
> > if constexpr (std::is_constant_evaluated())) { // condition is always
> `true`. Should use plain `if` instead.
> > foo_constexpr(x);
> > } else {
> > foo_runtime(x);
> > }
> > }
> > ```
> >
> >
> >
> > Reviewers: rsmith, MaskRay, bruno, void
> >
> > Reviewed By: rsmith
> >
> > Subscribers: dexonsmith, zoecarver, fdeazeve, kristina, cfe-commits
> >
> > Differential Revision: https://reviews.llvm.org/D55500
> >
> > Added:
> > cfe/trunk/test/CodeGenCXX/builtin-is-constant-evaluated.cpp
> > cfe/trunk/test/SemaCXX/builtin-is-constant-evaluated.cpp
> > Modified:
> > cfe/trunk/include/clang/Basic/Builtins.def
> > cfe/trunk/lib/AST/ExprConstant.cpp
> > cfe/trunk/lib/Basic/Builtins.cpp
> > cfe/trunk/lib/CodeGen/CGDecl.cpp
> > cfe/trunk/test/Sema/builtins.c
> >
> > Modified: cfe/trunk/include/clang/Basic/Builtins.def
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Builtins.def?rev=359067&r1=359066&r2=359067&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/include/clang/Basic/Builtins.def (original)
> > +++ cfe/trunk/include/clang/Basic/Builtins.def Tue Apr 23 19:23:30 2019
> > @@ -500,6 +500,7 @@ BUILTIN(__builtin_vsprintf, "ic*cC*a", "
> > BUILTIN(__builtin_vsnprintf, "ic*zcC*a", "nFP:2:")
> > BUILTIN(__builtin_thread_pointer, "v*", "nc")
> > BUILTIN(__builtin_launder, "v*v*", "nt")
> > +LANGBUILTIN(__builtin_is_constant_evaluated, "b", "n", CXX_LANG)
> >
> > // GCC exception builtins
> > BUILTIN(__builtin_eh_return, "vzv*", "r") // FIXME: Takes intptr_t, not
> size_t!
> >
> > Modified: cfe/trunk/lib/AST/ExprConstant.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=359067&r1=359066&r2=359067&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
> > +++ cfe/trunk/lib/AST/ExprConstant.cpp Tue Apr 23 19:23:30 2019
> > @@ -8279,6 +8279,9 @@ bool IntExprEvaluator::VisitBuiltinCallE
> > return Success(false, E);
> > }
> >
> > + case Builtin::BI__builtin_is_constant_evaluated:
> > + return Success(Info.InConstantContext, E);
> > +
> > case Builtin::BI__builtin_ctz:
> > case Builtin::BI__builtin_ctzl:
> > case Builtin::BI__builtin_ctzll:
> > @@ -11139,6 +11142,7 @@ bool Expr::EvaluateAsConstantExpr(EvalRe
> > EvalInfo::EvaluationMode EM = EvalInfo::EM_ConstantExpression;
> > EvalInfo Info(Ctx, Result, EM);
> > Info.InConstantContext = true;
> > +
> > if (!::Evaluate(Result.Val, Info, this))
> > return false;
> >
> >
> > Modified: cfe/trunk/lib/Basic/Builtins.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Basic/Builtins.cpp?rev=359067&r1=359066&r2=359067&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/lib/Basic/Builtins.cpp (original)
> > +++ cfe/trunk/lib/Basic/Builtins.cpp Tue Apr 23 19:23:30 2019
> > @@ -75,9 +75,12 @@ bool Builtin::Context::builtinIsSupporte
> > bool OclCUnsupported = !LangOpts.OpenCL &&
> > (BuiltinInfo.Langs & ALL_OCLC_LANGUAGES);
> > bool OpenMPUnsupported = !LangOpts.OpenMP && BuiltinInfo.Langs ==
> OMP_LANG;
> > + bool CPlusPlusUnsupported =
> > + !LangOpts.CPlusPlus && BuiltinInfo.Langs == CXX_LANG;
> > return !BuiltinsUnsupported && !MathBuiltinsUnsupported &&
> !OclCUnsupported &&
> > !OclC1Unsupported && !OclC2Unsupported && !OpenMPUnsupported &&
> > - !GnuModeUnsupported && !MSModeUnsupported && !ObjCUnsupported;
> > + !GnuModeUnsupported && !MSModeUnsupported && !ObjCUnsupported
> &&
> > + !CPlusPlusUnsupported;
> > }
> >
> > /// initializeBuiltins - Mark the identifiers for all the builtins with
> their
> >
> > Modified: cfe/trunk/lib/CodeGen/CGDecl.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDecl.cpp?rev=359067&r1=359066&r2=359067&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/lib/CodeGen/CGDecl.cpp (original)
> > +++ cfe/trunk/lib/CodeGen/CGDecl.cpp Tue Apr 23 19:23:30 2019
> > @@ -1783,7 +1783,8 @@ void CodeGenFunction::EmitAutoVarInit(co
> > }
> >
> > llvm::Constant *constant = nullptr;
> > - if (emission.IsConstantAggregate || D.isConstexpr()) {
> > + if (emission.IsConstantAggregate || D.isConstexpr() ||
> > + D.isUsableInConstantExpressions(getContext())) {
> > assert(!capturedByInit && "constant init contains a capturing
> block?");
> > constant = ConstantEmitter(*this).tryEmitAbstractForInitializer(D);
> > if (constant && trivialAutoVarInit !=
> >
> > Added: cfe/trunk/test/CodeGenCXX/builtin-is-constant-evaluated.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/builtin-is-constant-evaluated.cpp?rev=359067&view=auto
> >
> ==============================================================================
> > --- cfe/trunk/test/CodeGenCXX/builtin-is-constant-evaluated.cpp (added)
> > +++ cfe/trunk/test/CodeGenCXX/builtin-is-constant-evaluated.cpp Tue Apr
> 23 19:23:30 2019
> > @@ -0,0 +1,133 @@
> > +// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm %s
> -std=c++2a -o %t.ll
> > +// RUN: FileCheck -check-prefix=CHECK-FN-CG -input-file=%t.ll %s
> > +// RUN: FileCheck -check-prefix=CHECK-STATIC -input-file=%t.ll %s
> > +// RUN: FileCheck -check-prefix=CHECK-DYN -input-file=%t.ll %s
> > +// RUN: FileCheck -check-prefix=CHECK-ARR -input-file=%t.ll %s
> > +// RUN: FileCheck -check-prefix=CHECK-FOLD -input-file=%t.ll %s
> > +
> > +using size_t = decltype(sizeof(int));
> > +
> > +#define CONSTINIT __attribute__((require_constant_initialization))
> > +
> > +extern "C" [[noreturn]] void BOOM();
> > +extern "C" void OK();
> > +extern "C" size_t RANDU();
> > +
> > +namespace std {
> > +inline constexpr bool is_constant_evaluated() noexcept {
> > + return __builtin_is_constant_evaluated();
> > +}
> > +} // namespace std
> > +
> > +// CHECK-FN-CG-LABEL: define zeroext i1 @_Z3foov()
> > +// CHECK-FN-CG: ret i1 false
> > +bool foo() {
> > + return __builtin_is_constant_evaluated();
> > +}
> > +
> > +// CHECK-FN-CG-LABEL: define linkonce_odr i32 @_Z1fv()
> > +constexpr int f() {
> > + // CHECK-FN-CG: store i32 13, i32* %n, align 4
> > + // CHECK-FN-CG: store i32 17, i32* %m, align 4
> > + // CHECK-FN-CG: %1 = load i32, i32* %m, align 4
> > + // CHECK-FN-CG: %add = add nsw i32 %1, 13
> > + // CHECK-FN-CG: ret i32 %add
> > + const int n = __builtin_is_constant_evaluated() &&
> std::is_constant_evaluated() ? 13 : 17; // n == 13
> > + int m = __builtin_is_constant_evaluated() ? 13 : 17; // m might
> be 13 or 17 (see below)
> > + char arr[n] = {}; // char[13]
> > + return m + int(sizeof(arr));
> > +}
> > +
> > +// CHECK-STATIC-DAG: @p = global i32 26,
> > +CONSTINIT int p = f(); // f().m == 13; initialized to 26
> > +// CHECK-STATIC-DAG: @p2 = global i32 26,
> > +int p2 = f(); // same result without CONSTINIT
> > +
> > +// CHECK-DYN-LABEL: define internal void @__cxx_global_var_init()
> > +// CHECK-DYN: %0 = load i32, i32* @p, align 4
> > +// CHECK-DYN-NEXT: %call = call i32 @_Z1fv()
> > +// CHECK-DYN-NEXT: %add = add nsw i32 %0, %call
> > +// CHECK-DYN-NEXT: store i32 %add, i32* @q, align 4
> > +// CHECK-DYN-NEXT: ret void
> > +int q = p + f(); // m == 17 for this call; initialized to 56
> > +
> > +int y;
> > +
> > +// CHECK-STATIC-DAG: @b = global i32 2,
> > +CONSTINIT int b = __builtin_is_constant_evaluated() ? 2 : y; // static
> initialization to 2
> > +
> > +// CHECK-DYN-LABEL: define internal void @__cxx_global_var_init.1()
> > +// CHECK-DYN: %0 = load i32, i32* @y, align 4
> > +// CHECK-DYN: %1 = load i32, i32* @y, align 4
> > +// CHECK-DYN-NEXT: %add = add
> > +// CHECK-DYN-NEXT: store i32 %add, i32* @c,
> > +int c = y + (__builtin_is_constant_evaluated() ? 2 : y); // dynamic
> initialization to y+y
> > +
> > +// CHECK-DYN-LABEL: define internal void @__cxx_global_var_init.2()
> > +// CHECK-DYN: store i32 1, i32* @_ZL1a, align 4
> > +// CHECK-DYN-NEXT: ret void
> > +const int a = __builtin_is_constant_evaluated() ? y : 1; // dynamic
> initialization to 1
> > +const int *a_sink = &a;
> > +
> > +// CHECK-ARR-LABEL: define void @_Z13test_arr_exprv
> > +void test_arr_expr() {
> > + // CHECK-ARR: %x1 = alloca [101 x i8],
> > + char x1[std::is_constant_evaluated() &&
> __builtin_is_constant_evaluated() ? 101 : 1];
> > +
> > + // CHECK-ARR: %x2 = alloca [42 x i8],
> > + char x2[std::is_constant_evaluated() &&
> __builtin_is_constant_evaluated() ? 42 : RANDU()];
> > +
> > + // CHECK-ARR: call i8* @llvm.stacksave()
> > + // CHECK-ARR: %vla = alloca i8, i64 13,
> > + char x3[std::is_constant_evaluated() ||
> __builtin_is_constant_evaluated() ? RANDU() : 13];
> > +}
> > +
> > +// CHECK-ARR-LABEL: define void @_Z17test_new_arr_exprv
> > +void test_new_arr_expr() {
> > + // CHECK-ARR: call i8* @_Znam(i64 17)
> > + new char[std::is_constant_evaluated() ||
> __builtin_is_constant_evaluated() ? 1 : 17];
> > +}
> > +
> > +// CHECK-FOLD-LABEL: @_Z31test_constant_initialized_locali(
> > +bool test_constant_initialized_local(int k) {
> > + // CHECK-FOLD: store i8 1, i8* %n,
> > + // CHECK-FOLD: store volatile i8* %n, i8** %p,
> > + const bool n = __builtin_is_constant_evaluated() &&
> std::is_constant_evaluated();
> > + const bool *volatile p = &n;
> > + return *p;
> > +}
> > +
> > +// CHECK-FOLD-LABEL: define void @_Z21test_ir_constant_foldv()
> > +void test_ir_constant_fold() {
> > + // CHECK-FOLD-NEXT: entry:
> > + // CHECK-FOLD-NEXT: call void @OK()
> > + // CHECK-FOLD-NEXT: call void @OK()
> > + // CHECK-FOLD-NEXT: ret void
> > + if (std::is_constant_evaluated()) {
> > + BOOM();
> > + } else {
> > + OK();
> > + }
> > + std::is_constant_evaluated() ? BOOM() : OK();
> > +}
> > +
> > +// CHECK-STATIC-DAG: @ir = constant i32* @i_constant,
> > +int i_constant;
> > +int i_not_constant;
> > +int &ir = __builtin_is_constant_evaluated() ? i_constant :
> i_not_constant;
> > +
> > +// CHECK-FOLD-LABEL: @_Z35test_ref_initialization_local_scopev()
> > +void test_ref_initialization_local_scope() {
> > + const int i_constant = 42;
> > + const int i_non_constant = 101;
> > + // CHECK-FOLD: store i32* %i_non_constant, i32** %r,
> > + const int &r = __builtin_is_constant_evaluated() ? i_constant :
> i_non_constant;
> > +}
> > +
> > +// CHECK-FOLD-LABEL: @_Z22test_ref_to_static_varv()
> > +void test_ref_to_static_var() {
> > + static int i_constant = 42;
> > + static int i_non_constant = 101;
> > + // CHECK-FOLD: store i32* @_ZZ22test_ref_to_static_varvE10i_constant,
> i32** %r,
> > + int &r = __builtin_is_constant_evaluated() ? i_constant :
> i_non_constant;
> > +}
> > \ No newline at end of file
> >
> > Modified: cfe/trunk/test/Sema/builtins.c
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/builtins.c?rev=359067&r1=359066&r2=359067&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/test/Sema/builtins.c (original)
> > +++ cfe/trunk/test/Sema/builtins.c Tue Apr 23 19:23:30 2019
> > @@ -314,3 +314,9 @@ void test23() {
> > memcpy(buf, src, 11); // expected-warning{{'memcpy' will always
> overflow; destination buffer has size 10, but size argument is 11}}
> > my_memcpy(buf, src, 11); // expected-warning{{'memcpy' will always
> overflow; destination buffer has size 10, but size argument is 11}}
> > }
> > +
> > +// Test that __builtin_is_constant_evaluated() is not allowed in C
> > +int test_cxx_builtin() {
> > + // expected-error at +1 {{use of unknown builtin
> '__builtin_is_constant_evaluated'}}
> > + return __builtin_is_constant_evaluated();
> > +}
> >
> > Added: cfe/trunk/test/SemaCXX/builtin-is-constant-evaluated.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/builtin-is-constant-evaluated.cpp?rev=359067&view=auto
> >
> ==============================================================================
> > --- cfe/trunk/test/SemaCXX/builtin-is-constant-evaluated.cpp (added)
> > +++ cfe/trunk/test/SemaCXX/builtin-is-constant-evaluated.cpp Tue Apr 23
> 19:23:30 2019
> > @@ -0,0 +1,121 @@
> > +// RUN: %clang_cc1 -std=c++2a -verify %s -fcxx-exceptions
> -triple=x86_64-linux-gnu
> > +
> > +using size_t = decltype(sizeof(int));
> > +
> > +namespace std {
> > +inline constexpr bool is_constant_evaluated() noexcept {
> > + return __builtin_is_constant_evaluated();
> > +}
> > +} // namespace std
> > +
> > +extern int dummy; // expected-note 1+ {{declared here}}
> > +
> > +static_assert(__builtin_is_constant_evaluated());
> > +static_assert(noexcept(__builtin_is_constant_evaluated()));
> > +
> > +constexpr bool b = __builtin_is_constant_evaluated();
> > +static_assert(b);
> > +
> > +const int n = __builtin_is_constant_evaluated() ? 4 : dummy;
> > +static_assert(n == 4);
> > +constexpr int cn = __builtin_is_constant_evaluated() ? 11 : dummy;
> > +static_assert(cn == 11);
> > +// expected-error at +1 {{'bn' must be initialized by a constant
> expression}}
> > +constexpr int bn = __builtin_is_constant_evaluated() ? dummy : 42; //
> expected-note {{non-const variable 'dummy' is not allowed}}
> > +
> > +const int n2 = __builtin_is_constant_evaluated() ? dummy : 42; //
> expected-note {{declared here}}
> > +static_assert(n2 == 42); //
> expected-error {{static_assert expression is not an integral constant}}
> > +// expected-note at -1 {{initializer of 'n2' is not a constant
> expression}}
> > +
> > +template <bool V, bool Default = std::is_constant_evaluated()>
> > +struct Templ { static_assert(V); static_assert(Default); };
> > +Templ<__builtin_is_constant_evaluated()> x; // type X<true>
> > +
> > +template <class T>
> > +void test_if_constexpr() {
> > + if constexpr (__builtin_is_constant_evaluated()) {
> > + static_assert(__is_same(T, int));
> > + } else {
> > + using Test = typename T::DOES_NOT_EXIST;
> > + }
> > +}
> > +template void test_if_constexpr<int>();
> > +
> > +void test_array_decl() {
> > + char x[__builtin_is_constant_evaluated() +
> std::is_constant_evaluated()];
> > + static_assert(sizeof(x) == 2, "");
> > +}
> > +
> > +void test_case_stmt(int x) {
> > + switch (x) {
> > + case 0:
> // OK
> > + case __builtin_is_constant_evaluated():
> // expected-note {{previous case}}
> > + case std::is_constant_evaluated() +
> __builtin_is_constant_evaluated(): // expected-note {{previous case}}
> > + case 1:
> // expected-error {{duplicate case value '1'}}
> > + case 2:
> // expected-error {{duplicate case value '2'}}
> > + break;
> > + }
> > +}
> > +
> > +constexpr size_t good_array_size() {
> > + return std::is_constant_evaluated() ? 42 : static_cast<size_t>(-1);
> > +}
> > +
> > +constexpr size_t bad_array_size() {
> > + return std::is_constant_evaluated() ? static_cast<size_t>(-1) : 13;
> > +}
> > +
> > +template <class T>
> > +constexpr T require_constexpr(T v) {
> > + if (!std::is_constant_evaluated())
> > + throw "BOOM";
> > + return v;
> > +}
> > +
> > +void test_new_expr() {
> > + constexpr size_t TooLarge = -1;
> > + auto *x = new int[std::is_constant_evaluated() ? 1 : TooLarge];
> // expected-error {{array is too large}}
> > + auto *x2 = new int[std::is_constant_evaluated() ? TooLarge : 1];
> // OK
> > + auto *y = new int[1][std::is_constant_evaluated() ? TooLarge : 1]{};
> // expected-error {{array is too large}}
> > + auto *y2 = new int[1][require_constexpr(42)];
> > +}
> > +
> > +void test_alignas_operand() {
> > + alignas(std::is_constant_evaluated() ? 8 : 2) char dummy;
> > + static_assert(__alignof(dummy) == 8);
> > +}
> > +
> > +void test_static_assert_operand() {
> > + static_assert(std::is_constant_evaluated(), "");
> > +}
> > +
> > +void test_enumerator() {
> > + enum MyEnum {
> > + ZERO = 0,
> > + ONE = std::is_constant_evaluated()
> > + };
> > + static_assert(ONE == 1, "");
> > +}
> > +
> > +struct TestBitfieldWidth {
> > + unsigned Bits : std::is_constant_evaluated();
> > +};
> > +
> > +void test_operand_of_noexcept_fn()
> noexcept(std::is_constant_evaluated());
> > +static_assert(noexcept(test_operand_of_noexcept_fn()), "");
> > +
> > +
> > +namespace test_ref_initialization {
> > +int x;
> > +int y;
> > +int &r = __builtin_is_constant_evaluated() ? x : y;
> > +static_assert(&r == &x);
> > +
> > +} // namespace test_ref_initialization
> > +
> > +#if defined(__cpp_conditional_explicit)
> > +struct TestConditionalExplicit {
> > + explicit(__builtin_is_constant_evaluated())
> TestConditionalExplicit(int) {}
> > +};
> > +TestConditionalExplicit e = 42;
> > +#endif
> >
> >
> > _______________________________________________
> > cfe-commits mailing list
> > cfe-commits at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20190424/d0547edf/attachment-0001.html>
More information about the cfe-commits
mailing list