r292555 - P0426: Make the library implementation of constexpr char_traits a little easier
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Thu Jan 19 17:22:55 PST 2017
Hans, can we get this onto the Clang 4 release branch (along with the
documentation added in r292558 and fixed in r292559)? This will allow us to
avoid libc++ carrying a version test for Clang, and allow it to cleanly
finish off its implementation of P0426.
On 19 January 2017 at 16:45, Richard Smith via cfe-commits <
cfe-commits at lists.llvm.org> wrote:
> Author: rsmith
> Date: Thu Jan 19 18:45:35 2017
> New Revision: 292555
>
> URL: http://llvm.org/viewvc/llvm-project?rev=292555&view=rev
> Log:
> P0426: Make the library implementation of constexpr char_traits a little
> easier
> by providing a memchr builtin that returns char* instead of void*.
>
> Also add a __has_feature flag to indicate the presence of constexpr forms
> of
> the relevant <string> functions.
>
> Modified:
> cfe/trunk/include/clang/Basic/Builtins.def
> cfe/trunk/lib/AST/ExprConstant.cpp
> cfe/trunk/lib/CodeGen/CGBuiltin.cpp
> cfe/trunk/lib/Lex/PPMacroExpansion.cpp
> cfe/trunk/test/CodeGenCXX/builtins.cpp
> cfe/trunk/test/Lexer/has_feature_cxx0x.cpp
> cfe/trunk/test/SemaCXX/constexpr-string.cpp
>
> Modified: cfe/trunk/include/clang/Basic/Builtins.def
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/
> clang/Basic/Builtins.def?rev=292555&r1=292554&r2=292555&view=diff
> ============================================================
> ==================
> --- cfe/trunk/include/clang/Basic/Builtins.def (original)
> +++ cfe/trunk/include/clang/Basic/Builtins.def Thu Jan 19 18:45:35 2017
> @@ -1339,6 +1339,7 @@ BUILTIN(__builtin_smulll_overflow, "bSLL
> BUILTIN(__builtin_addressof, "v*v&", "nct")
> BUILTIN(__builtin_operator_new, "v*z", "c")
> BUILTIN(__builtin_operator_delete, "vv*", "n")
> +BUILTIN(__builtin_char_memchr, "c*cC*iz", "n")
>
> // Safestack builtins
> BUILTIN(__builtin___get_unsafe_stack_start, "v*", "Fn")
>
> Modified: cfe/trunk/lib/AST/ExprConstant.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/
> ExprConstant.cpp?rev=292555&r1=292554&r2=292555&view=diff
> ============================================================
> ==================
> --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
> +++ cfe/trunk/lib/AST/ExprConstant.cpp Thu Jan 19 18:45:35 2017
> @@ -5683,6 +5683,7 @@ bool PointerExprEvaluator::VisitBuiltinC
> case Builtin::BI__builtin_strchr:
> case Builtin::BI__builtin_wcschr:
> case Builtin::BI__builtin_memchr:
> + case Builtin::BI__builtin_char_memchr:
> case Builtin::BI__builtin_wmemchr: {
> if (!Visit(E->getArg(0)))
> return false;
> @@ -5720,6 +5721,7 @@ bool PointerExprEvaluator::VisitBuiltinC
> // Fall through.
> case Builtin::BImemchr:
> case Builtin::BI__builtin_memchr:
> + case Builtin::BI__builtin_char_memchr:
> // memchr compares by converting both sides to unsigned char.
> That's also
> // correct for strchr if we get this far (to cope with plain char
> being
> // unsigned in the strchr case).
>
> Modified: cfe/trunk/lib/CodeGen/CGBuiltin.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/
> CGBuiltin.cpp?rev=292555&r1=292554&r2=292555&view=diff
> ============================================================
> ==================
> --- cfe/trunk/lib/CodeGen/CGBuiltin.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGBuiltin.cpp Thu Jan 19 18:45:35 2017
> @@ -1189,6 +1189,10 @@ RValue CodeGenFunction::EmitBuiltinExpr(
> return RValue::get(Dest.getPointer());
> }
>
> + case Builtin::BI__builtin_char_memchr:
> + BuiltinID = Builtin::BI__builtin_memchr;
> + break;
> +
> case Builtin::BI__builtin___memcpy_chk: {
> // fold __builtin_memcpy_chk(x, y, cst1, cst2) to memcpy iff
> cst1<=cst2.
> llvm::APSInt Size, DstSize;
>
> Modified: cfe/trunk/lib/Lex/PPMacroExpansion.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Lex/
> PPMacroExpansion.cpp?rev=292555&r1=292554&r2=292555&view=diff
> ============================================================
> ==================
> --- cfe/trunk/lib/Lex/PPMacroExpansion.cpp (original)
> +++ cfe/trunk/lib/Lex/PPMacroExpansion.cpp Thu Jan 19 18:45:35 2017
> @@ -1183,6 +1183,7 @@ static bool HasFeature(const Preprocesso
> .Case("cxx_attributes", LangOpts.CPlusPlus11)
> .Case("cxx_auto_type", LangOpts.CPlusPlus11)
> .Case("cxx_constexpr", LangOpts.CPlusPlus11)
> + .Case("cxx_constexpr_string_builtins", LangOpts.CPlusPlus11)
> .Case("cxx_decltype", LangOpts.CPlusPlus11)
> .Case("cxx_decltype_incomplete_return_types", LangOpts.CPlusPlus11)
> .Case("cxx_default_function_template_args", LangOpts.CPlusPlus11)
>
> Modified: cfe/trunk/test/CodeGenCXX/builtins.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/
> CodeGenCXX/builtins.cpp?rev=292555&r1=292554&r2=292555&view=diff
> ============================================================
> ==================
> --- cfe/trunk/test/CodeGenCXX/builtins.cpp (original)
> +++ cfe/trunk/test/CodeGenCXX/builtins.cpp Thu Jan 19 18:45:35 2017
> @@ -26,3 +26,7 @@ int x = __builtin_abs(-2);
> long y = __builtin_abs(-2l);
> // CHECK: [[Y:%.+]] = call i64 @_Z13__builtin_absl(i64 -2)
> // CHECK: store i64 [[Y]], i64* @y, align 8
> +
> +extern const char char_memchr_arg[32];
> +char *memchr_result = __builtin_char_memchr(char_memchr_arg, 123, 32);
> +// CHECK: call i8* @memchr(i8* getelementptr inbounds ([32 x i8], [32 x
> i8]* @char_memchr_arg, i32 0, i32 0), i32 123, i64 32)
>
> Modified: cfe/trunk/test/Lexer/has_feature_cxx0x.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Lexer/
> has_feature_cxx0x.cpp?rev=292555&r1=292554&r2=292555&view=diff
> ============================================================
> ==================
> --- cfe/trunk/test/Lexer/has_feature_cxx0x.cpp (original)
> +++ cfe/trunk/test/Lexer/has_feature_cxx0x.cpp Thu Jan 19 18:45:35 2017
> @@ -301,6 +301,17 @@ int no_constexpr();
> // CHECK-11: has_constexpr
> // CHECK-NO-11: no_constexpr
>
> +#if __has_feature(cxx_constexpr_string_builtins)
> +int has_constexpr_string_builtins();
> +#else
> +int no_constexpr_string_builtins();
> +#endif
> +
> +// CHECK-1Z: has_constexpr_string_builtins
> +// CHECK-14: has_constexpr_string_builtins
> +// CHECK-11: has_constexpr_string_builtins
> +// CHECK-NO-11: no_constexpr_string_builtins
> +
> #if __has_feature(cxx_generalized_initializers)
> int has_generalized_initializers();
> #else
>
> Modified: cfe/trunk/test/SemaCXX/constexpr-string.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/
> SemaCXX/constexpr-string.cpp?rev=292555&r1=292554&r2=292555&view=diff
> ============================================================
> ==================
> --- cfe/trunk/test/SemaCXX/constexpr-string.cpp (original)
> +++ cfe/trunk/test/SemaCXX/constexpr-string.cpp Thu Jan 19 18:45:35 2017
> @@ -166,6 +166,27 @@ namespace StrchrEtc {
> static_assert(__builtin_memchr(nullptr, 'x', 3) == nullptr); //
> expected-error {{not an integral constant}} expected-note {{dereferenced
> null}}
> static_assert(__builtin_memchr(nullptr, 'x', 0) == nullptr); // FIXME:
> Should we reject this?
>
> + static_assert(__builtin_char_memchr(kStr, 'a', 0) == nullptr);
> + static_assert(__builtin_char_memchr(kStr, 'a', 1) == kStr);
> + static_assert(__builtin_char_memchr(kStr, '\0', 5) == nullptr);
> + static_assert(__builtin_char_memchr(kStr, '\0', 6) == kStr + 5);
> + static_assert(__builtin_char_memchr(kStr, '\xff', 8) == kStr + 4);
> + static_assert(__builtin_char_memchr(kStr, '\xff' + 256, 8) == kStr +
> 4);
> + static_assert(__builtin_char_memchr(kStr, '\xff' - 256, 8) == kStr +
> 4);
> + static_assert(__builtin_char_memchr(kFoo, 'x', 3) == nullptr);
> + static_assert(__builtin_char_memchr(kFoo, 'x', 4) == nullptr); //
> expected-error {{not an integral constant}} expected-note {{dereferenced
> one-past-the-end}}
> + static_assert(__builtin_char_memchr(nullptr, 'x', 3) == nullptr); //
> expected-error {{not an integral constant}} expected-note {{dereferenced
> null}}
> + static_assert(__builtin_char_memchr(nullptr, 'x', 0) == nullptr); //
> FIXME: Should we reject this?
> +
> + static_assert(*__builtin_char_memchr(kStr, '\xff', 8) == '\xff');
> + constexpr bool char_memchr_mutable() {
> + char buffer[] = "mutable";
> + *__builtin_char_memchr(buffer, 't', 8) = 'r';
> + *__builtin_char_memchr(buffer, 'm', 8) = 'd';
> + return __builtin_strcmp(buffer, "durable") == 0;
> + }
> + static_assert(char_memchr_mutable());
> +
> constexpr bool a = !strchr("hello", 'h'); // expected-error {{constant
> expression}} expected-note {{non-constexpr function 'strchr' cannot be used
> in a constant expression}}
> constexpr bool b = !memchr("hello", 'h', 3); // expected-error
> {{constant expression}} expected-note {{non-constexpr function 'memchr'
> cannot be used in a constant expression}}
> }
>
>
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