i965/fs: Refactor handling of constant tg4 offsets

Previously, we had an OFFSET_VALUE source for logical texture instructions
that was intended to mean exactly what it says, "offset".  In reality, we
only fully used it for tg4 offsets.  We used offset_value.file == IMM to
mean, "you have a constant offset, go look in instr->offset" and didn't
actually use the contents of the register at all in that case except for
in nir_emit_texture where we used it as a temporary before we copy it into
instr->offset.

This commit renames OFFSET_VALUE to TG4_OFFSET and restricts its usage to
indirect tg4 offsets only.  The nir_emit_texture code is refactored so that
we explicitly build a header_bits value which is placed in instr->offset
and the constant offset values (both for tg4 and regular texture
operations) are used to construct header_bits and don't go through the
offset source at all.  Finally, we stop passing offset_value in to
lower_sampler_logical_send_gen5 because we can't do indirect offsets until
gen7 anyway.

Reviewed-by: Kenneth Graunke <[email protected]>

3 files changed, 29 insertions, 34 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_defines.h b/src/mesa/drivers/dri/i965/brw_defines.h
index 84a51b48cc6..f22a52f7394 100644
--- a/src/mesa/drivers/dri/i965/brw_defines.h
+++ b/src/mesa/drivers/dri/i965/brw_defines.h
@@ -1420,7 +1420,7 @@ enum tex_logical_srcs {
    /** Texture sampler index */
    TEX_LOGICAL_SRC_SAMPLER,
    /** Texel offset for gathers */
-   TEX_LOGICAL_SRC_OFFSET_VALUE,
+   TEX_LOGICAL_SRC_TG4_OFFSET,
    /** REQUIRED: Number of coordinate components (as UD immediate) */
    TEX_LOGICAL_SRC_COORD_COMPONENTS,
    /** REQUIRED: Number of derivative components (as UD immediate) */
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 3cdf0bf39f7..c218f56684d 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -730,7 +730,7 @@ fs_inst::components_read(unsigned i) const
                opcode == SHADER_OPCODE_TXD_LOGICAL)
          return src[TEX_LOGICAL_SRC_GRAD_COMPONENTS].ud;
       /* Texture offset. */
-      else if (i == TEX_LOGICAL_SRC_OFFSET_VALUE)
+      else if (i == TEX_LOGICAL_SRC_TG4_OFFSET)
          return 2;
       /* MCS */
       else if (i == TEX_LOGICAL_SRC_MCS && opcode == SHADER_OPCODE_TXF_CMS_W_LOGICAL)
@@ -3877,7 +3877,6 @@ lower_sampler_logical_send_gen5(const fs_builder &bld, fs_inst *inst, opcode op,
                                 const fs_reg &sample_index,
                                 const fs_reg &surface,
                                 const fs_reg &sampler,
-                                const fs_reg &offset_value,
                                 unsigned coord_components,
                                 unsigned grad_components)
 {
@@ -3885,7 +3884,7 @@ lower_sampler_logical_send_gen5(const fs_builder &bld, fs_inst *inst, opcode op,
    fs_reg msg_coords = message;
    unsigned header_size = 0;
 
-   if (offset_value.file != BAD_FILE) {
+   if (inst->offset != 0) {
       /* The offsets set up by the visitor are in the m1 header, so we can't
        * go headerless.
        */
@@ -3985,7 +3984,7 @@ lower_sampler_logical_send_gen7(const fs_builder &bld, fs_inst *inst, opcode op,
                                 const fs_reg &mcs,
                                 const fs_reg &surface,
                                 const fs_reg &sampler,
-                                const fs_reg &offset_value,
+                                const fs_reg &tg4_offset,
                                 unsigned coord_components,
                                 unsigned grad_components)
 {
@@ -3997,7 +3996,7 @@ lower_sampler_logical_send_gen7(const fs_builder &bld, fs_inst *inst, opcode op,
       sources[i] = bld.vgrf(BRW_REGISTER_TYPE_F);
 
    if (op == SHADER_OPCODE_TG4 || op == SHADER_OPCODE_TG4_OFFSET ||
-       offset_value.file != BAD_FILE || inst->eot ||
+       inst->offset != 0 || inst->eot ||
        op == SHADER_OPCODE_SAMPLEINFO ||
        is_high_sampler(devinfo, sampler)) {
       /* For general texture offsets (no txf workaround), we need a header to
@@ -4142,7 +4141,7 @@ lower_sampler_logical_send_gen7(const fs_builder &bld, fs_inst *inst, opcode op,
 
       for (unsigned i = 0; i < 2; i++) /* offu, offv */
          bld.MOV(retype(sources[length++], BRW_REGISTER_TYPE_D),
-                 offset(offset_value, bld, i));
+                 offset(tg4_offset, bld, i));
 
       if (coord_components == 3) /* r if present */
          bld.MOV(sources[length++], offset(coordinate, bld, 2));
@@ -4194,7 +4193,7 @@ lower_sampler_logical_send(const fs_builder &bld, fs_inst *inst, opcode op)
    const fs_reg &mcs = inst->src[TEX_LOGICAL_SRC_MCS];
    const fs_reg &surface = inst->src[TEX_LOGICAL_SRC_SURFACE];
    const fs_reg &sampler = inst->src[TEX_LOGICAL_SRC_SAMPLER];
-   const fs_reg &offset_value = inst->src[TEX_LOGICAL_SRC_OFFSET_VALUE];
+   const fs_reg &tg4_offset = inst->src[TEX_LOGICAL_SRC_TG4_OFFSET];
    assert(inst->src[TEX_LOGICAL_SRC_COORD_COMPONENTS].file == IMM);
    const unsigned coord_components = inst->src[TEX_LOGICAL_SRC_COORD_COMPONENTS].ud;
    assert(inst->src[TEX_LOGICAL_SRC_GRAD_COMPONENTS].file == IMM);
@@ -4203,12 +4202,12 @@ lower_sampler_logical_send(const fs_builder &bld, fs_inst *inst, opcode op)
    if (devinfo->gen >= 7) {
       lower_sampler_logical_send_gen7(bld, inst, op, coordinate,
                                       shadow_c, lod, lod2, sample_index,
-                                      mcs, surface, sampler, offset_value,
+                                      mcs, surface, sampler, tg4_offset,
                                       coord_components, grad_components);
    } else if (devinfo->gen >= 5) {
       lower_sampler_logical_send_gen5(bld, inst, op, coordinate,
                                       shadow_c, lod, lod2, sample_index,
-                                      surface, sampler, offset_value,
+                                      surface, sampler,
                                       coord_components, grad_components);
    } else {
       lower_sampler_logical_send_gen4(bld, inst, op, coordinate,
@@ -4677,7 +4676,7 @@ get_sampler_lowered_simd_width(const struct gen_device_info *devinfo,
       inst->components_read(TEX_LOGICAL_SRC_LOD2) +
       inst->components_read(TEX_LOGICAL_SRC_SAMPLE_INDEX) +
       (inst->opcode == SHADER_OPCODE_TG4_OFFSET_LOGICAL ?
-       inst->components_read(TEX_LOGICAL_SRC_OFFSET_VALUE) : 0) +
+       inst->components_read(TEX_LOGICAL_SRC_TG4_OFFSET) : 0) +
       inst->components_read(TEX_LOGICAL_SRC_MCS);
 
    /* SIMD16 messages with more than five arguments exceed the maximum message
diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index c88fa77472c..baa973c31a0 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -4431,6 +4431,7 @@ fs_visitor::nir_emit_texture(const fs_builder &bld, nir_tex_instr *instr)
    if (instr->sampler_dim == GLSL_SAMPLER_DIM_BUF)
       srcs[TEX_LOGICAL_SRC_LOD] = brw_imm_d(0);
 
+   uint32_t header_bits = 0;
    for (unsigned i = 0; i < instr->num_srcs; i++) {
       fs_reg src = get_nir_src(instr->src[i].src);
       switch (instr->src[i].src_type) {
@@ -4485,11 +4486,9 @@ fs_visitor::nir_emit_texture(const fs_builder &bld, nir_tex_instr *instr)
          nir_const_value *const_offset =
             nir_src_as_const_value(instr->src[i].src);
          if (const_offset) {
-            unsigned header_bits = brw_texture_offset(const_offset->i32, 3);
-            if (header_bits != 0)
-               srcs[TEX_LOGICAL_SRC_OFFSET_VALUE] = brw_imm_ud(header_bits);
+            header_bits |= brw_texture_offset(const_offset->i32, 3);
          } else {
-            srcs[TEX_LOGICAL_SRC_OFFSET_VALUE] =
+            srcs[TEX_LOGICAL_SRC_TG4_OFFSET] =
                retype(src, BRW_REGISTER_TYPE_D);
          }
          break;
@@ -4607,8 +4606,7 @@ fs_visitor::nir_emit_texture(const fs_builder &bld, nir_tex_instr *instr)
       opcode = SHADER_OPCODE_LOD_LOGICAL;
       break;
    case nir_texop_tg4:
-      if (srcs[TEX_LOGICAL_SRC_OFFSET_VALUE].file != BAD_FILE &&
-          srcs[TEX_LOGICAL_SRC_OFFSET_VALUE].file != IMM)
+      if (srcs[TEX_LOGICAL_SRC_TG4_OFFSET].file != BAD_FILE)
          opcode = SHADER_OPCODE_TG4_OFFSET_LOGICAL;
       else
          opcode = SHADER_OPCODE_TG4_LOGICAL;
@@ -4639,8 +4637,21 @@ fs_visitor::nir_emit_texture(const fs_builder &bld, nir_tex_instr *instr)
       unreachable("unknown texture opcode");
    }
 
+   if (instr->op == nir_texop_tg4) {
+      if (instr->component == 1 &&
+          key_tex->gather_channel_quirk_mask & (1 << texture)) {
+         /* gather4 sampler is broken for green channel on RG32F --
+          * we must ask for blue instead.
+          */
+         header_bits |= 2 << 16;
+      } else {
+         header_bits |= instr->component << 16;
+      }
+   }
+
    fs_reg dst = bld.vgrf(brw_type_for_nir_type(instr->dest_type), 4);
    fs_inst *inst = bld.emit(opcode, dst, srcs, ARRAY_SIZE(srcs));
+   inst->offset = header_bits;
 
    const unsigned dest_size = nir_tex_instr_dest_size(instr);
    if (devinfo->gen >= 9 &&
@@ -4658,23 +4669,8 @@ fs_visitor::nir_emit_texture(const fs_builder &bld, nir_tex_instr *instr)
    if (srcs[TEX_LOGICAL_SRC_SHADOW_C].file != BAD_FILE)
       inst->shadow_compare = true;
 
-   if (srcs[TEX_LOGICAL_SRC_OFFSET_VALUE].file == IMM)
-      inst->offset = srcs[TEX_LOGICAL_SRC_OFFSET_VALUE].ud;
-
-   if (instr->op == nir_texop_tg4) {
-      if (instr->component == 1 &&
-          key_tex->gather_channel_quirk_mask & (1 << texture)) {
-         /* gather4 sampler is broken for green channel on RG32F --
-          * we must ask for blue instead.
-          */
-         inst->offset |= 2 << 16;
-      } else {
-         inst->offset |= instr->component << 16;
-      }
-
-      if (devinfo->gen == 6)
-         emit_gen6_gather_wa(key_tex->gen6_gather_wa[texture], dst);
-   }
+   if (instr->op == nir_texop_tg4 && devinfo->gen == 6)
+      emit_gen6_gather_wa(key_tex->gen6_gather_wa[texture], dst);
 
    fs_reg nir_dest[4];
    for (unsigned i = 0; i < dest_size; i++)