[Mesa-dev] [PATCH] i965/emit: Do the sampler index adjustment directly in header.0.3

[Jason Ekstrand]

Prior to this commit, the adjust_sampler_state_pointer function took an
extra register that it could use as scratch space.  The usual candidate was
the destination of the sampler instruction.  However, if that register ever
aliased anything important such as the sampler index, this would scratch
all over important data.  Fortunately, the calculation is such that we can
just do it in place and we don't need the scratch space at all.

Cc: Chris Forbes <chrisf at ijw.co.nz>
---
 src/mesa/drivers/dri/i965/brw_eu.h               | 3 +--
 src/mesa/drivers/dri/i965/brw_eu_emit.c          | 5 ++---
 src/mesa/drivers/dri/i965/brw_fs_generator.cpp   | 2 +-
 src/mesa/drivers/dri/i965/brw_vec4_generator.cpp | 2 +-
 4 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_eu.h b/src/mesa/drivers/dri/i965/brw_eu.h
index 22d5a0a..a94ea42 100644
--- a/src/mesa/drivers/dri/i965/brw_eu.h
+++ b/src/mesa/drivers/dri/i965/brw_eu.h
@@ -283,8 +283,7 @@ void brw_SAMPLE(struct brw_compile *p,
 
 void brw_adjust_sampler_state_pointer(struct brw_compile *p,
                                       struct brw_reg header,
-                                      struct brw_reg sampler_index,
-                                      struct brw_reg scratch);
+                                      struct brw_reg sampler_index);
 
 void gen4_math(struct brw_compile *p,
 	       struct brw_reg dest,
diff --git a/src/mesa/drivers/dri/i965/brw_eu_emit.c b/src/mesa/drivers/dri/i965/brw_eu_emit.c
index c26bed2..39b2022 100644
--- a/src/mesa/drivers/dri/i965/brw_eu_emit.c
+++ b/src/mesa/drivers/dri/i965/brw_eu_emit.c
@@ -2383,8 +2383,7 @@ void brw_SAMPLE(struct brw_compile *p,
  */
 void brw_adjust_sampler_state_pointer(struct brw_compile *p,
                                       struct brw_reg header,
-                                      struct brw_reg sampler_index,
-                                      struct brw_reg scratch)
+                                      struct brw_reg sampler_index)
 {
    /* The "Sampler Index" field can only store values between 0 and 15.
     * However, we can add an offset to the "Sampler State Pointer"
@@ -2414,7 +2413,7 @@ void brw_adjust_sampler_state_pointer(struct brw_compile *p,
          return;
       }
 
-      struct brw_reg temp = vec1(retype(scratch, BRW_REGISTER_TYPE_UD));
+      struct brw_reg temp = get_element_ud(header, 3);
 
       brw_AND(p, temp, get_element_ud(sampler_index, 0), brw_imm_ud(0x0f0));
       brw_SHL(p, temp, temp, brw_imm_ud(4));
diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
index d473739..4474902 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
@@ -697,7 +697,7 @@ fs_generator::generate_tex(fs_inst *inst, struct brw_reg dst, struct brw_reg src
                        brw_imm_ud(inst->offset));
          }
 
-         brw_adjust_sampler_state_pointer(p, header_reg, sampler_index, dst);
+         brw_adjust_sampler_state_pointer(p, header_reg, sampler_index);
          brw_pop_insn_state(p);
       }
    }
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp b/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
index fd37a05..cb9ad6f 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
@@ -354,7 +354,7 @@ vec4_generator::generate_tex(vec4_instruction *inst,
          if (dw2)
             brw_MOV(p, get_element_ud(header, 2), brw_imm_ud(dw2));
 
-         brw_adjust_sampler_state_pointer(p, header, sampler_index, dst);
+         brw_adjust_sampler_state_pointer(p, header, sampler_index);
          brw_pop_insn_state(p);
       }
    }
-- 
2.2.1