yaxunl added inline comments.
================
Comment at: lib/AST/ASTContext.cpp:9547-9555
+unsigned ASTContext::getTargetAddressSpace(unsigned AS) const {
+ // For OpenCL, the address space qualifier is 0 in AST.
+ if (AS == 0 && LangOpts.OpenCL)
+ return getTargetInfo().getDataLayout().getAllocaAddrSpace();
+ if (AS < LangAS::Offset || AS >= LangAS::Offset + LangAS::Count)
+ return AS;
+ else
----------------
t-tye wrote:
> Presumably this will not work if the user put an address space attribute on a
> variable with an address space of 0, since it is not possible to distinguish
> between a variable that never had an attribute and was function local, and
> one that has an explicit address space attribute specifying 0.
>
> It would seem better if LangAS did not map the 0..LangAS::Offset to be target
> address spaces. Instead LangAS could use 0..LangAS::Count to be the CLANG
> explicitly specified values (reserving 0 to mean the default when none was
> specified), and values above LangAS::Count would map to the explicitly
> specified target address spaces. For example:
>
> ```
> namespace clang {
>
> namespace LangAS {
>
> /// \brief Defines the set of possible language-specific address spaces.
> ///
> /// This uses values above the language-specific address spaces to denote
> /// the target-specific address spaces biased by target_first.
> enum ID {
> default = 0,
>
> opencl_global,
> opencl_local,
> opencl_constant,
> opencl_generic,
>
> cuda_device,
> cuda_constant,
> cuda_shared,
>
> Count,
>
> target_first = Count
> };
>
> /// The type of a lookup table which maps from language-specific address
> spaces
> /// to target-specific ones.
> typedef unsigned Map[Count];
>
> }
> ```
>
> Then this function would be:
>
> ```
> unsigned ASTContext::getTargetAddressSpace(unsigned AS) const {
> if (AS == LangAS::default && LangOpts.OpenCL)
> // For OpenCL, only function local variables are not explicitly marked
> with an
> // address space in the AST, and these need to be the address space of
> alloca.
> return getTargetInfo().getDataLayout().getAllocaAddrSpace();
> if (AS >= LangAS::target_first)
> return AS - LangAS::target_first;
> else
> return (*AddrSpaceMap)[AS];
> }
> ```
>
> Each target AddrSpaceMap would map LangAS::default to that target's default
> generic address space since that matches most other languages.
>
> The address space attribute would need a corresponding "+
> LangAS::target_first" to the value it stored in the AST.
>
> Then it is possible to definitively tell when an AST node has not had any
> address space specified as it will be the LangAS::default value.
There is a lit test like this:
```
// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only
#define OPENCL_CONSTANT 8388354
int __attribute__((address_space(OPENCL_CONSTANT))) c[3] = {0};
void foo() {
c[0] = 1; //expected-error{{read-only variable is not assignable}}
}
```
It tries to set address space of opencl_constant through
`__attribute__((address_space(n)))`. If we "+ LangAS::target_first" to the
value before it is tored in the AST, we are not able to use
`__attribute__((address_space(n)))` to represent opencl_constant.
https://reviews.llvm.org/D31404
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