[cfe-dev] Address space extensions (adding type modifier keywords)

[Phil Tomson via cfe-dev]

Our architecture has a somewhat different memory model with three different
address spaces: local, block, global.

Some time ago (prior to my involvement in our project) our address space
extensions were added to the frontend so that we can write:

volatile   int v_i;
xstglocal  int l_i;
xstgblock  int b_i;
xstgglobal int g_i;

volatile   int* p_vi;       // Regular pointer to volatile integer
xstglocal  int* p_li;       // Regular pointer to local integer
xstgblock  int* b_pi;       // Regular pointer to block integer
xstgglobal int* g_pi;       // Regular pointer to global integer

int* volatile   vp_i;       // Volatile pointer to regular integer

These address space modifiers (xstglocal, xstgblock, xstgglobal) are used
to determine which address space data is stored in. The above will compile
just fine.

However, originally this work was done for clang/llvm 3.2. After we moved
to 3.6 we found that the following (which used to work in 3.2) no longer
works in 3.6:

int* xstglocal  lp_i;       // Local pointer to any integer
int* xstgblock  b_pi;       // Block pointer to any integer
int* xstgglobal g_pi;       // Global pointer to any integer

xstgglobal int* xstglocal  vp_li;   // Local pointer to global integer
xstglocal  int* xstgblock  vp_bi;   // Block pointer to local integer
xstgblock  int* xstgglobal vp_gi;   // Global pointer to block integer

These result in front end errors:

issue.c:13:7: error: expected identifier or '('
int * xstglocal  lp_i;       // Local pointer to any integer
      ^
issue.c:14:7: error: expected identifier or '('
int * xstgblock  b_pi;       // Block pointer to any integer
      ^
issue.c:15:7: error: expected identifier or '('
int * xstgglobal g_pi;       // Global pointer to any integer
      ^
issue.c:20:18: error: expected identifier or '('
xstgglobal int * xstglocal  vp_li;   // Local pointer to global integer
                 ^
issue.c:21:18: error: expected identifier or '('
xstglocal  int * xstgblock  vp_bi;   // Block pointer to local integer
                 ^
issue.c:22:18: error: expected identifier or '('
xstgblock  int * xstgglobal vp_gi;   // Global pointer to block integer
                 ^
6 errors generated.

It looks as though these address space extension keywords were added in
TokenKinds.def:
// XSTG address space qualifiers
KEYWORD(xstgglobal                  , KEYXSTG)
KEYWORD(xstgblock                   , KEYXSTG)
KEYWORD(xstglocal                   , KEYXSTG)

As well as in Attr.td:

def XSTGLocalAddressSpace : TypeAttr {
  let Spellings = [Keyword<"xstglocal">];
  let Documentation = [Undocumented];
}

def XSTGBlockAddressSpace : TypeAttr {
  let Spellings = [Keyword<"xstgblock">];
  let Documentation = [Undocumented];
}

def XSTGGlobalAddressSpace : TypeAttr {
  let Spellings = [Keyword<"xstgglobal">];
  let Documentation = [Undocumented];
}

with some support in ParseDecl.cpp.

Was there an API change between clang 3.2 and 3.6 that might have broken
this? Any pointers on how I might fix these errors?

Thanks.

Phil
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