[PATCH] [OpenCL] Add string literals to the constant address space.

[Eli Friedman]

On Wed, Jun 5, 2013 at 1:09 PM, Tanya Lattner <lattner at apple.com> wrote:

> Regarding the change to SemaType. My one concern is that the type is now
> "const", which I think is confusing to the user when they see the error
> message and also I think it emits warnings if someone does const __constant
> in their source. What I did was change the IsModifiable() function in
> lib/AST/ExprClassification.cpp to treat anything in constaddr space as
> ConstQualified in . What do you think about this approach instead?
>

Also worth noting: technically, I think the OpenCL standard requires us to
reject this program:

int f(__constant int*);
int f(const __constant int* x) {
  return *x;
}

In practice, I'm not sure anyone would notice.

-Eli


>
> Otherwise, the patch looks ok to me.
>
> -Tanya
>
>
> On May 31, 2013, at 6:35 AM, Joey Gouly <joey.gouly at arm.com> wrote:
>
> >  I forgot to add the CodeGen parts of this patch to the review, here it
> is.
> >
> > http://llvm-reviews.chandlerc.com/D894
> >
> > CHANGE SINCE LAST DIFF
> >  http://llvm-reviews.chandlerc.com/D894?vs=2205&id=2209#toc
> >
> > Files:
> >  lib/CodeGen/CodeGenModule.cpp
> >  lib/Frontend/CompilerInvocation.cpp
> >  lib/Sema/SemaExpr.cpp
> >  lib/Sema/SemaType.cpp
> >  test/CodeGenOpenCL/opencl_types.cl
> >  test/CodeGenOpenCL/str_literals.cl
> >  test/SemaOpenCL/address-spaces.cl
> >  test/SemaOpenCL/str_literals.cl
> >
> > Index: lib/CodeGen/CodeGenModule.cpp
> > ===================================================================
> > --- lib/CodeGen/CodeGenModule.cpp
> > +++ lib/CodeGen/CodeGenModule.cpp
> > @@ -2668,11 +2668,16 @@
> >   llvm::Constant *C =
> >       llvm::ConstantDataArray::getString(CGM.getLLVMContext(), str,
> false);
> >
> > +  // OpenCL v1.1 s6.5.3: a string literal is in the constant address
> space.
> > +  unsigned AddrSpace = 0;
> > +  if (CGM.getLangOpts().OpenCL)
> > +    AddrSpace =
> CGM.getContext().getTargetAddressSpace(LangAS::opencl_constant);
> > +
> >   // Create a global variable for this string
> > -  llvm::GlobalVariable *GV =
> > -    new llvm::GlobalVariable(CGM.getModule(), C->getType(), constant,
> > -                             llvm::GlobalValue::PrivateLinkage,
> > -                             C, GlobalName);
> > +  llvm::GlobalVariable *GV = new llvm::GlobalVariable(
> > +      CGM.getModule(), C->getType(), constant,
> > +      llvm::GlobalValue::PrivateLinkage, C, GlobalName, 0,
> > +      llvm::GlobalVariable::NotThreadLocal, AddrSpace);
> >   GV->setAlignment(Alignment);
> >   GV->setUnnamedAddr(true);
> >   return GV;
> > Index: lib/Frontend/CompilerInvocation.cpp
> > ===================================================================
> > --- lib/Frontend/CompilerInvocation.cpp
> > +++ lib/Frontend/CompilerInvocation.cpp
> > @@ -1014,6 +1014,7 @@
> >     Opts.LaxVectorConversions = 0;
> >     Opts.DefaultFPContract = 1;
> >     Opts.NativeHalfType = 1;
> > +    Opts.ConstStrings = 1;
> >   }
> >
> >   if (LangStd == LangStandard::lang_cuda)
> > Index: lib/Sema/SemaExpr.cpp
> > ===================================================================
> > --- lib/Sema/SemaExpr.cpp
> > +++ lib/Sema/SemaExpr.cpp
> > @@ -1467,6 +1467,11 @@
> >   if (getLangOpts().CPlusPlus || getLangOpts().ConstStrings)
> >     StrTy.addConst();
> >
> > +  // OpenCL v1.1 s6.5.3: a string literal is in the constant address
> space.
> > +  if (getLangOpts().OpenCL) {
> > +    StrTy = Context.getAddrSpaceQualType(StrTy,
> LangAS::opencl_constant);
> > +  }
> > +
> >   // Get an array type for the string, according to C99 6.4.5.  This
> includes
> >   // the nul terminator character as well as the string length for pascal
> >   // strings.
> > Index: lib/Sema/SemaType.cpp
> > ===================================================================
> > --- lib/Sema/SemaType.cpp
> > +++ lib/Sema/SemaType.cpp
> > @@ -3829,6 +3829,10 @@
> >
> >   unsigned ASIdx = static_cast<unsigned>(addrSpace.getZExtValue());
> >   Type = S.Context.getAddrSpaceQualType(Type, ASIdx);
> > +
> > +  // Constant address space implies const qualifier
> > +  if(S.getLangOpts().OpenCL && ASIdx == LangAS::opencl_constant)
> > +    Type = S.Context.getConstType(Type);
> > }
> >
> > /// Does this type have a "direct" ownership qualifier?  That is,
> > Index: test/CodeGenOpenCL/opencl_types.cl
> > ===================================================================
> > --- test/CodeGenOpenCL/opencl_types.cl
> > +++ test/CodeGenOpenCL/opencl_types.cl
> > @@ -1,7 +1,7 @@
> > // RUN: %clang_cc1 %s -emit-llvm -o - -O0 | FileCheck %s
> >
> > constant sampler_t glb_smp = 7;
> > -// CHECK: global i32 7
> > +// CHECK: constant i32 7
> >
> > void fnc1(image1d_t img) {}
> > // CHECK: @fnc1(%opencl.image1d_t*
> > Index: test/CodeGenOpenCL/str_literals.cl
> > ===================================================================
> > --- /dev/null
> > +++ test/CodeGenOpenCL/str_literals.cl
> > @@ -0,0 +1,6 @@
> > +// RUN: %clang_cc1 %s -emit-llvm -o - -ffake-address-space-map |
> FileCheck %s
> > +
> > +__constant char * __constant x = "hello world";
> > +
> > +// CHECK: addrspace(3) unnamed_addr constant
> > +// CHECK: @x = addrspace(3) constant i8 addrspace(3)*
> > Index: test/SemaOpenCL/address-spaces.cl
> > ===================================================================
> > --- test/SemaOpenCL/address-spaces.cl
> > +++ test/SemaOpenCL/address-spaces.cl
> > @@ -9,5 +9,5 @@
> >   int *ip;
> >   ip = gip; // expected-error {{assigning '__global int *' to 'int *'
> changes address space of pointer}}
> >   ip = &li; // expected-error {{assigning '__local int *' to 'int *'
> changes address space of pointer}}
> > -  ip = &ci; // expected-error {{assigning '__constant int *' to 'int *'
> changes address space of pointer}}
> > +  ip = &ci; // expected-error {{assigning 'const __constant int *' to
> 'int *' changes address space of pointer}}
> > }
> > Index: test/SemaOpenCL/str_literals.cl
> > ===================================================================
> > --- /dev/null
> > +++ test/SemaOpenCL/str_literals.cl
> > @@ -0,0 +1,12 @@
> > +// RUN: %clang_cc1 %s -verify
> > +// expected-no-diagnostics
> > +
> > +__constant char * __constant x = "hello world";
> > +
> > +void foo(__constant char * a) {
> > +
> > +}
> > +
> > +void bar() {
> > +  foo("hello world");
> > +}
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