[cfe-commits] r156723 - in /cfe/trunk: include/clang/Basic/Attr.td lib/CodeGen/CodeGenModule.cpp lib/Sema/SemaDeclAttr.cpp test/CodeGen/attr-coldhot.c test/Sema/attr-coldhot.c

Nico Weber thakis at chromium.org
Sat May 12 18:19:54 PDT 2012


Should other unimplemented optimization attributes (e.g. "flatten") be
silently ignored instead of issuing a warning too? How do you decide which
attributes to warn on and which to ignore silently?

Nico

On Sat, May 12, 2012 at 2:10 PM, Benjamin Kramer
<benny.kra at googlemail.com>wrote:

> Author: d0k
> Date: Sat May 12 16:10:52 2012
> New Revision: 156723
>
> URL: http://llvm.org/viewvc/llvm-project?rev=156723&view=rev
> Log:
> Add support for __attribute__((hot)) and __attribute__((cold)).
>
> Currently cold functions are marked with the "optsize" attribute in CodeGen
> so they are always optimized for size.  The hot attribute is just ignored,
> LLVM doesn't have a way to express hotness at the moment.
>
> Added:
>    cfe/trunk/test/CodeGen/attr-coldhot.c
>    cfe/trunk/test/Sema/attr-coldhot.c
> Modified:
>    cfe/trunk/include/clang/Basic/Attr.td
>    cfe/trunk/lib/CodeGen/CodeGenModule.cpp
>    cfe/trunk/lib/Sema/SemaDeclAttr.cpp
>
> Modified: cfe/trunk/include/clang/Basic/Attr.td
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Attr.td?rev=156723&r1=156722&r2=156723&view=diff
>
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/Attr.td (original)
> +++ cfe/trunk/include/clang/Basic/Attr.td Sat May 12 16:10:52 2012
> @@ -243,6 +243,10 @@
>   let Args = [FunctionArgument<"FunctionDecl">];
>  }
>
> +def Cold : InheritableAttr {
> +  let Spellings = ["cold"];
> +}
> +
>  def Common : InheritableAttr {
>   let Spellings = ["common"];
>  }
> @@ -348,6 +352,10 @@
>   let Spellings = ["gnu_inline"];
>  }
>
> +def Hot : InheritableAttr {
> +  let Spellings = ["hot"];
> +}
> +
>  def IBAction : InheritableAttr {
>   let Spellings = ["ibaction"];
>  }
>
> Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=156723&r1=156722&r2=156723&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Sat May 12 16:10:52 2012
> @@ -523,6 +523,10 @@
>       !F->hasFnAttr(llvm::Attribute::NoInline))
>     F->addFnAttr(llvm::Attribute::AlwaysInline);
>
> +  // FIXME: Communicate hot and cold attributes to LLVM more directly.
> +  if (D->hasAttr<ColdAttr>())
> +    F->addFnAttr(llvm::Attribute::OptimizeForSize);
> +
>   if (isa<CXXConstructorDecl>(D) || isa<CXXDestructorDecl>(D))
>     F->setUnnamedAddr(true);
>
>
> Modified: cfe/trunk/lib/Sema/SemaDeclAttr.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDeclAttr.cpp?rev=156723&r1=156722&r2=156723&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaDeclAttr.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaDeclAttr.cpp Sat May 12 16:10:52 2012
> @@ -1294,6 +1294,46 @@
>                                          Str->getString()));
>  }
>
> +static void handleColdAttr(Sema &S, Decl *D, const AttributeList &Attr) {
> +  // Check the attribute arguments.
> +  if (!checkAttributeNumArgs(S, Attr, 0))
> +    return;
> +
> +  if (!isa<FunctionDecl>(D)) {
> +    S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type)
> +      << Attr.getName() << ExpectedFunction;
> +    return;
> +  }
> +
> +  if (D->hasAttr<HotAttr>()) {
> +    S.Diag(Attr.getLoc(), diag::err_attributes_are_not_compatible)
> +      << Attr.getName() << "hot";
> +    return;
> +  }
> +
> +  D->addAttr(::new (S.Context) ColdAttr(Attr.getRange(), S.Context));
> +}
> +
> +static void handleHotAttr(Sema &S, Decl *D, const AttributeList &Attr) {
> +  // Check the attribute arguments.
> +  if (!checkAttributeNumArgs(S, Attr, 0))
> +    return;
> +
> +  if (!isa<FunctionDecl>(D)) {
> +    S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type)
> +      << Attr.getName() << ExpectedFunction;
> +    return;
> +  }
> +
> +  if (D->hasAttr<ColdAttr>()) {
> +    S.Diag(Attr.getLoc(), diag::err_attributes_are_not_compatible)
> +      << Attr.getName() << "cold";
> +    return;
> +  }
> +
> +  D->addAttr(::new (S.Context) HotAttr(Attr.getRange(), S.Context));
> +}
> +
>  static void handleNakedAttr(Sema &S, Decl *D, const AttributeList &Attr) {
>   // Check the attribute arguments.
>   if (!checkAttributeNumArgs(S, Attr, 0))
> @@ -3825,6 +3865,8 @@
>   case AttributeList::AT_ownership_takes:
>   case AttributeList::AT_ownership_holds:
>       handleOwnershipAttr     (S, D, Attr); break;
> +  case AttributeList::AT_cold:        handleColdAttr        (S, D, Attr);
> break;
> +  case AttributeList::AT_hot:         handleHotAttr         (S, D, Attr);
> break;
>   case AttributeList::AT_naked:       handleNakedAttr       (S, D, Attr);
> break;
>   case AttributeList::AT_noreturn:    handleNoReturnAttr    (S, D, Attr);
> break;
>   case AttributeList::AT_nothrow:     handleNothrowAttr     (S, D, Attr);
> break;
>
> Added: cfe/trunk/test/CodeGen/attr-coldhot.c
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/attr-coldhot.c?rev=156723&view=auto
>
> ==============================================================================
> --- cfe/trunk/test/CodeGen/attr-coldhot.c (added)
> +++ cfe/trunk/test/CodeGen/attr-coldhot.c Sat May 12 16:10:52 2012
> @@ -0,0 +1,9 @@
> +// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s
> +
> +int test1() __attribute__((__cold__)) {
> +  return 42;
> +
> +// Check that we set the optsize attribute on the function.
> +// CHECK: @test1{{.*}}optsize
> +// CHECK: ret
> +}
>
> Added: cfe/trunk/test/Sema/attr-coldhot.c
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/attr-coldhot.c?rev=156723&view=auto
>
> ==============================================================================
> --- cfe/trunk/test/Sema/attr-coldhot.c (added)
> +++ cfe/trunk/test/Sema/attr-coldhot.c Sat May 12 16:10:52 2012
> @@ -0,0 +1,10 @@
> +// RUN: %clang_cc1 -fsyntax-only -verify %s
> +
> +int foo() __attribute__((__hot__));
> +int bar() __attribute__((__cold__));
> +
> +int var1 __attribute__((__cold__)); // expected-warning{{'__cold__'
> attribute only applies to functions}}
> +int var2 __attribute__((__hot__)); // expected-warning{{'__hot__'
> attribute only applies to functions}}
> +
> +int qux() __attribute__((__hot__)) __attribute__((__cold__)); //
> expected-error{{'__hot__' and cold attributes are not compatible}}
> +int baz() __attribute__((__cold__)) __attribute__((__hot__)); //
> expected-error{{'__cold__' and hot attributes are not compatible}}
>
>
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