[PATCH] Recognize _alloca as an alias for the alloca builtin

[Reid Kleckner]

Er, that didn't actually work.  I thought I finished this, but apparently
not...


On Wed, Oct 30, 2013 at 3:38 PM, Reid Kleckner <rnk at google.com> wrote:

>     - Make it only active in -fms-extensions.
>
> http://llvm-reviews.chandlerc.com/D1989
>
> CHANGE SINCE LAST DIFF
>   http://llvm-reviews.chandlerc.com/D1989?vs=5067&id=5275#toc
>
> Files:
>   include/clang/Basic/Builtins.def
>   include/clang/Basic/Builtins.h
>   lib/CodeGen/CGBuiltin.cpp
>   test/CodeGen/builtins.c
>   test/SemaCXX/no-implicit-builtin-decls.cpp
>
> Index: include/clang/Basic/Builtins.def
> ===================================================================
> --- include/clang/Basic/Builtins.def
> +++ include/clang/Basic/Builtins.def
> @@ -670,11 +670,12 @@
>  BUILTIN(__builtin_index, "c*cC*i", "Fn")
>  BUILTIN(__builtin_rindex, "c*cC*i", "Fn")
>
> -// Microsoft builtins.
> -BUILTIN(__assume, "vb", "n")
> -BUILTIN(__noop, "v.", "n")
> -BUILTIN(__debugbreak, "v", "n")
> -
> +// Microsoft builtins.  These are only active with -fms-extensions.
> +// They are not library builtins despire our use of LIBBUILTIN.
> +LIBBUILTIN(_alloca,      "v*z", "n", 0, ALL_MS_LANGUAGES)
> +LIBBUILTIN(__assume,     "vb",  "n", 0, ALL_MS_LANGUAGES)
> +LIBBUILTIN(__noop,       "v.",  "n", 0, ALL_MS_LANGUAGES)
> +LIBBUILTIN(__debugbreak, "v",   "n", 0, ALL_MS_LANGUAGES)
>
>  // C99 library functions
>  // C99 stdlib.h
> Index: include/clang/Basic/Builtins.h
> ===================================================================
> --- include/clang/Basic/Builtins.h
> +++ include/clang/Basic/Builtins.h
> @@ -35,8 +35,10 @@
>      C_LANG = 0x2,    // builtin for c only.
>      CXX_LANG = 0x4,  // builtin for cplusplus only.
>      OBJC_LANG = 0x8, // builtin for objective-c and objective-c++
> +    MS_LANG = 0x10,  // builtin requires MS mode.
>      ALL_LANGUAGES = C_LANG | CXX_LANG | OBJC_LANG, // builtin for all
> languages.
> -    ALL_GNU_LANGUAGES = ALL_LANGUAGES | GNU_LANG   // builtin requires
> GNU mode.
> +    ALL_GNU_LANGUAGES = ALL_LANGUAGES | GNU_LANG,  // builtin requires
> GNU mode.
> +    ALL_MS_LANGUAGES = ALL_LANGUAGES | MS_LANG     // builtin requires MS
> mode.
>    };
>
>  namespace Builtin {
> Index: lib/CodeGen/CGBuiltin.cpp
> ===================================================================
> --- lib/CodeGen/CGBuiltin.cpp
> +++ lib/CodeGen/CGBuiltin.cpp
> @@ -604,6 +604,7 @@
>    }
>
>    case Builtin::BIalloca:
> +  case Builtin::BI_alloca:
>    case Builtin::BI__builtin_alloca: {
>      Value *Size = EmitScalarExpr(E->getArg(0));
>      return RValue::get(Builder.CreateAlloca(Builder.getInt8Ty(), Size));
> Index: test/CodeGen/builtins.c
> ===================================================================
> --- test/CodeGen/builtins.c
> +++ test/CodeGen/builtins.c
> @@ -210,3 +210,11 @@
>    // CHECK: call i64 @llvm.readcyclecounter()
>    return __builtin_readcyclecounter();
>  }
> +
> +// CHECK-LABEL: define void @test_alloca
> +void test_alloca(int n) {
> +  extern void capture(void *);
> +  capture(_alloca(n));
> +  // CHECK: alloca i8, i64 %
> +  // CHECK: call void @capture
> +}
> Index: test/SemaCXX/no-implicit-builtin-decls.cpp
> ===================================================================
> --- test/SemaCXX/no-implicit-builtin-decls.cpp
> +++ test/SemaCXX/no-implicit-builtin-decls.cpp
> @@ -1,6 +1,6 @@
>  // RUN: %clang_cc1 -fsyntax-only -verify %s
>
> -void f() {
> +void f() { // expected-note at +1 {{declared here}}
>    void *p = malloc(sizeof(int) * 10); // expected-error{{use of
> undeclared identifier 'malloc'}}
>  }
>
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