[Mesa-dev] [RFC mesa] nouveau: Add support for OpenCL global memory buffers

[Hans de Goede]

This little "hack" fixes the use of OpenCL global memory buffers with
nouveau, but clearly the #if 0 is not a solution as it breaks buffers
with GLSL.

The reason I'm posting this as an RFC patch is to discuss how to solve
this properly, 2 solutions come to mind:

1) Use separate nv50_ir::FILE_MEMORY_xxx values for buffers versus
   TGSI_FILE_MEMORY with TGSI_MEMORY_TYPE_GLOBAL, looking at translateFile()
   we currently have:

   case TGSI_FILE_BUFFER:          return nv50_ir::FILE_MEMORY_GLOBAL;
   case TGSI_FILE_MEMORY:          return nv50_ir::FILE_MEMORY_GLOBAL;

   So doing a s/nv50_ir::FILE_MEMORY_GLOBAL/nv50_ir::FILE_MEMORY_BUFFER/
   everywhere and then adding a new FILE_MEMORY_GLOBAL seems like an
   obvious fix.

   But I'm afraid that we will have similar issues with OpenCL using
   flat addresses where as GLSL will have some implied base-address /
   offset in other places too, which brings me to solution 2:

2) Add a flag to Program to indicate that it is an OpenCL compute kernel;
   or possible use a different Program::TYPE_* for OpenCL ?

   I've a feeling that this is what we want since the addressing models
   are just different and we likely will need to implement different behavior
   in various places based on this.

   This will also allow us to use INPUT and CONST in tgsi code build from
   OpenCL programs and use that flag to do the right thing, rather then
   introducing new MEMORY[x], INPUT resp. MEMORY[x], CONST declarations
   for this.

   I'm esp. worried that once GLSL gets global support it will want
   different behavior for TGSI_FILE_MEMORY with TGSI_MEMORY_TYPE_GLOBAL
   then OpenCL, just like things are now with buffers, rendering solution
   1. a non solution

So I'm seeking input on how to move forward with this ...  ?

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
 src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp     | 4 ++++
 src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
index de0c72b..15012ac 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
@@ -1525,6 +1525,10 @@ Converter::makeSym(uint tgsiFile, int fileIdx, int idx, int c, uint32_t address)
 
    if (tgsiFile == TGSI_FILE_MEMORY) {
       switch (code->memoryFiles[fileIdx].mem_type) {
+      case TGSI_MEMORY_TYPE_GLOBAL:
+         /* No-op this is the default for TGSI_FILE_MEMORY */
+         sym->setFile(FILE_MEMORY_GLOBAL);
+         break;
       case TGSI_MEMORY_TYPE_SHARED:
          sym->setFile(FILE_MEMORY_SHARED);
          break;
diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
index 6cb4dd4..bcc96de 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
@@ -2106,6 +2106,7 @@ NVC0LoweringPass::visit(Instruction *i)
       } else if (i->src(0).getFile() == FILE_SHADER_OUTPUT) {
          assert(prog->getType() == Program::TYPE_TESSELLATION_CONTROL);
          i->op = OP_VFETCH;
+#if 0
       } else if (i->src(0).getFile() == FILE_MEMORY_GLOBAL) {
          Value *ind = i->getIndirect(0, 1);
          Value *ptr = loadResInfo64(ind, i->getSrc(0)->reg.fileIndex * 16);
@@ -2126,6 +2127,7 @@ NVC0LoweringPass::visit(Instruction *i)
          if (i->defExists(0)) {
             bld.mkMov(i->getDef(0), bld.mkImm(0));
          }
+#endif
       }
       break;
    case OP_ATOM:
-- 
2.7.2