[Mesa-dev] [PATCH] nvc0/ir: be careful about propagating very large offsets into const load

[Ilia Mirkin]

Indirect constbuf indexing works by using very large offsets. However if
an indirect constbuf index load is const-propagated, it becomes a very
large const offset. Take that into account when legalizing the SSA by
moving the high parts of that offset into the file index. Also disallow
very large (or small) indices on most other instructions.

This fixes regressions in ubo_array_indexing/*-two-arrays piglit tests.

Fixes: abd326e81b (nv50/ir: propagate indirect loads into instructions)
Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---
 src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp |  6 ++++++
 src/gallium/drivers/nouveau/codegen/nv50_ir_target.h          |  2 +-
 src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.cpp   | 10 ++++++++++
 src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.h     |  2 ++
 4 files changed, 19 insertions(+), 1 deletion(-)

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 64edffa..3806213 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
@@ -540,6 +540,12 @@ NVC0LegalizePostRA::visit(BasicBlock *bb)
          // It seems like barriers are never required for tessellation since
          // the warp size is 32, and there are always at most 32 tcs threads.
          bb->remove(i);
+      } else
+      if (i->op == OP_LOAD && i->subOp == NV50_IR_SUBOP_LDC_IS) {
+         int offset = i->src(0).get()->reg.data.offset;
+         if (abs(offset) > 0x10000)
+            i->src(0).get()->reg.fileIndex += offset >> 16;
+         i->src(0).get()->reg.data.offset = (int)(short)offset;
       } else {
          // TODO: Move this to before register allocation for operations that
          // need the $c register !
diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_target.h b/src/gallium/drivers/nouveau/codegen/nv50_ir_target.h
index 673f881..e6e1912 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_target.h
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_target.h
@@ -192,7 +192,7 @@ public:
    virtual bool insnCanLoad(const Instruction *insn, int s,
                             const Instruction *ld) const = 0;
    virtual bool insnCanLoadOffset(const Instruction *insn, int s,
-                                  int offset) const { return true; }
+                                  int offset) const = 0;
    virtual bool isOpSupported(operation, DataType) const = 0;
    virtual bool isAccessSupported(DataFile, DataType) const = 0;
    virtual bool isModSupported(const Instruction *,
diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.cpp
index 014c652..e40547c 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.cpp
@@ -384,6 +384,16 @@ TargetNVC0::insnCanLoad(const Instruction *i, int s,
 }
 
 bool
+TargetNVC0::insnCanLoadOffset(const Instruction *insn, int s, int offset) const
+{
+   const ValueRef& ref = insn->src(s);
+   if (ref.getFile() == FILE_MEMORY_CONST &&
+       (insn->op != OP_LOAD || insn->subOp != NV50_IR_SUBOP_LDC_IS))
+      return offset > -0x7fff && offset < 0x8000;
+   return true;
+}
+
+bool
 TargetNVC0::isAccessSupported(DataFile file, DataType ty) const
 {
    if (ty == TYPE_NONE)
diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.h b/src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.h
index 3c5c748..7d11cd9 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.h
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_target_nvc0.h
@@ -48,6 +48,8 @@ public:
 
    virtual bool insnCanLoad(const Instruction *insn, int s,
                             const Instruction *ld) const;
+   virtual bool insnCanLoadOffset(const Instruction *insn, int s,
+                                  int offset) const;
    virtual bool isOpSupported(operation, DataType) const;
    virtual bool isAccessSupported(DataFile, DataType) const;
    virtual bool isModSupported(const Instruction *, int s, Modifier) const;
-- 
2.4.10