i965/vec4: Add support for non-const sampler indices in generator

Signed-off-by: Chris Forbes <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>

1 files changed, 51 insertions, 1 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp b/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
index 2bf72c17862..1b1e64773e6 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
@@ -383,7 +383,57 @@ vec4_generator::generate_tex(vec4_instruction *inst,
 
       brw_mark_surface_used(&prog_data->base, sampler + base_binding_table_index);
    } else {
-      /* XXX: Non-constant sampler index. */
+      /* Non-constant sampler index. */
+      /* Note: this clobbers `dst` as a temporary before emitting the send */
+
+      struct brw_reg addr = vec1(retype(brw_address_reg(0), BRW_REGISTER_TYPE_UD));
+      struct brw_reg temp = vec1(retype(dst, BRW_REGISTER_TYPE_UD));
+
+      struct brw_reg sampler_reg = vec1(retype(sampler_index, BRW_REGISTER_TYPE_UD));
+
+      brw_push_insn_state(p);
+      brw_set_default_mask_control(p, BRW_MASK_DISABLE);
+      brw_set_default_access_mode(p, BRW_ALIGN_1);
+
+      /* Some care required: `sampler` and `temp` may alias:
+       *    addr = sampler & 0xff
+       *    temp = (sampler << 8) & 0xf00
+       *    addr = addr | temp
+       */
+      brw_ADD(p, addr, sampler_reg, brw_imm_ud(base_binding_table_index));
+      brw_SHL(p, temp, sampler_reg, brw_imm_ud(8u));
+      brw_AND(p, temp, temp, brw_imm_ud(0x0f00));
+      brw_AND(p, addr, addr, brw_imm_ud(0x0ff));
+      brw_OR(p, addr, addr, temp);
+
+      /* a0.0 |= <descriptor> */
+      brw_inst *insn_or = brw_next_insn(p, BRW_OPCODE_OR);
+      brw_set_sampler_message(p, insn_or,
+                              0 /* surface */,
+                              0 /* sampler */,
+                              msg_type,
+                              1 /* rlen */,
+                              inst->mlen /* mlen */,
+                              inst->header_present /* header */,
+                              BRW_SAMPLER_SIMD_MODE_SIMD4X2,
+                              return_format);
+      brw_inst_set_exec_size(p->brw, insn_or, BRW_EXECUTE_1);
+      brw_inst_set_src1_reg_type(p->brw, insn_or, BRW_REGISTER_TYPE_UD);
+      brw_set_src0(p, insn_or, addr);
+      brw_set_dest(p, insn_or, addr);
+
+
+      /* dst = send(offset, a0.0) */
+      brw_inst *insn_send = brw_next_insn(p, BRW_OPCODE_SEND);
+      brw_set_dest(p, insn_send, dst);
+      brw_set_src0(p, insn_send, src);
+      brw_set_indirect_send_descriptor(p, insn_send, BRW_SFID_SAMPLER, addr);
+
+      brw_pop_insn_state(p);
+
+      /* visitor knows more than we do about the surface limit required,
+       * so has already done marking.
+       */
    }
 }