[AMDGPU] Temporarily change constant address space from 4 to 2

[yaxunl]

Summary

Our final address space mapping is to let constant address space to be 4 to match nvptx. However for now we will make it 2 to avoid unnecessary work in FE/BE/devlib about intrinsics returning constant pointers.

[arsenm]

LGTM

[t-tye]

LGTM

lib/Target/AMDGPU/AMDGPU.h

 struct AMDGPUAS {
   // The following address space values depend on the triple environment.
   unsigned PRIVATE_ADDRESS;  ///< Address space for private memory.
-  unsigned CONSTANT_ADDRESS; ///< Address space for constant memory (VTX2)
   unsigned FLAT_ADDRESS;     ///< Address space for flat memory.
   unsigned REGION_ADDRESS;   ///< Address space for region memory.
 

   const static unsigned MAX_COMMON_ADDRESS = 5;
 
   const static unsigned GLOBAL_ADDRESS   = 1;  ///< Address space for global memory (RAT0, VTX0).
+  const static unsigned CONSTANT_ADDRESS = 2;  ///< Address space for constant memory (VTX2)
   const static unsigned LOCAL_ADDRESS    = 3;  ///< Address space for local memory.
   const static unsigned PARAM_D_ADDRESS  = 6;  ///< Address space for direct addressible parameter memory (CONST0)
   const static unsigned PARAM_I_ADDRESS  = 7;  ///< Address space for indirect addressible parameter memory (VTX1)

lib/Target/AMDGPU/AMDGPUAliasAnalysis.cpp

   /* Region   */ {NoAlias , NoAlias , NoAlias , NoAlias , MayAlias, MayAlias}
   };
   static const AliasResult ASAliasRulesGenIsZero[6][6] = {
-  /*             Flat       Global    Region    Group     Constant  Private */
+  /*             Flat       Global    Constant  Group     Region    Private */
   /* Flat     */ {MayAlias, MayAlias, MayAlias, MayAlias, MayAlias, MayAlias},
   /* Global   */ {MayAlias, MayAlias, NoAlias , NoAlias , NoAlias , NoAlias},
-  /* Region   */ {NoAlias , NoAlias , MayAlias, NoAlias,  NoAlias , MayAlias},
+  /* Constant */ {MayAlias, NoAlias , MayAlias, NoAlias , NoAlias,  NoAlias},
   /* Group    */ {MayAlias, NoAlias , NoAlias , MayAlias, NoAlias , NoAlias},
-  /* Constant */ {MayAlias, NoAlias , NoAlias , NoAlias , MayAlias, NoAlias},
+  /* Region   */ {MayAlias, NoAlias , NoAlias , NoAlias,  MayAlias, NoAlias},
   /* Private  */ {MayAlias, NoAlias , NoAlias , NoAlias , NoAlias , MayAlias}
   };
   assert(AS.MAX_COMMON_ADDRESS <= 5);
   if (AS.FLAT_ADDRESS == 0) {
     assert(AS.GLOBAL_ADDRESS   == 1 &&
-           AS.REGION_ADDRESS   == 2 &&
+           AS.REGION_ADDRESS   == 4 &&
            AS.LOCAL_ADDRESS    == 3 &&
-           AS.CONSTANT_ADDRESS == 4 &&
+           AS.CONSTANT_ADDRESS == 2 &&
            AS.PRIVATE_ADDRESS  == 5);
     ASAliasRules = &ASAliasRulesGenIsZero;
   } else {

lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

   // flat.
   if (TT.getEnvironmentName() == "amdgiz" ||
       TT.getEnvironmentName() == "amdgizcl")
-    return "e-p:64:64-p1:64:64-p2:64:64-p3:32:32-p4:64:64-p5:32:32"
+    return "e-p:64:64-p1:64:64-p2:64:64-p3:32:32-p4:32:32-p5:32:32"
          "-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128"
          "-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-A5";
   return "e-p:32:32-p1:64:64-p2:64:64-p3:32:32-p4:64:64-p5:32:32"

lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp

   AMDGPUAS AS;
   if (Env == "amdgiz" || Env == "amdgizcl") {
     AS.FLAT_ADDRESS     = 0;
-    AS.CONSTANT_ADDRESS = 4;
     AS.PRIVATE_ADDRESS  = 5;
-    AS.REGION_ADDRESS   = 2;
+    AS.REGION_ADDRESS   = 4;
   }
   else {
     AS.FLAT_ADDRESS     = 4;
-    AS.CONSTANT_ADDRESS = 2;
     AS.PRIVATE_ADDRESS  = 0;
     AS.REGION_ADDRESS   = 5;
    }