[Mesa-dev] [PATCH 3/3] i965: Set ExecSize to 16 for loop instructions in SIMD16 shaders.

[Kenneth Graunke]

Previously, we explicitly set the execution size to BRW_EXECUTE_8 and
disabled compression for loop instructions.  I can't imagine how this
could be correct in SIMD16 mode.

Looking at the history, it appears that this code has used BRW_EXECUTE_8
since 2007, when we had a SIMD8 backend that supported control flow and
a separate SIMD16 backend that didn't.  Presumably, when we added SIMD16
support for shaders with control flow, we simply neglected to update it.

Note that Gen4-5 don't support SIMD16 on shaders with control flow.

This might be a candidate for stable, but would need to be rewritten
completely due to the brw_inst API changes in master.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_eu_emit.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

These patches were tested with Piglit on Haswell, Sandybridge, and Ironlake.
No regressions.

diff --git a/src/mesa/drivers/dri/i965/brw_eu_emit.c b/src/mesa/drivers/dri/i965/brw_eu_emit.c
index 3be4449..e894abd 100644
--- a/src/mesa/drivers/dri/i965/brw_eu_emit.c
+++ b/src/mesa/drivers/dri/i965/brw_eu_emit.c
@@ -1526,7 +1526,8 @@ brw_BREAK(struct brw_compile *p)
                                   p->if_depth_in_loop[p->loop_stack_depth]);
    }
    brw_inst_set_qtr_control(brw, insn, BRW_COMPRESSION_NONE);
-   brw_inst_set_exec_size(brw, insn, BRW_EXECUTE_8);
+   brw_inst_set_exec_size(brw, insn, p->compressed ? BRW_EXECUTE_16
+                                                   : BRW_EXECUTE_8);
 
    return insn;
 }
@@ -1546,9 +1547,9 @@ brw_CONT(struct brw_compile *p)
       brw_inst_set_gen4_pop_count(brw, insn,
                                   p->if_depth_in_loop[p->loop_stack_depth]);
    }
-
    brw_inst_set_qtr_control(brw, insn, BRW_COMPRESSION_NONE);
-   brw_inst_set_exec_size(brw, insn, BRW_EXECUTE_8);
+   brw_inst_set_exec_size(brw, insn, p->compressed ? BRW_EXECUTE_16
+                                                   : BRW_EXECUTE_8);
    return insn;
 }
 
@@ -1664,7 +1665,8 @@ brw_WHILE(struct brw_compile *p)
       brw_set_src1(p, insn, brw_imm_ud(0));
       brw_inst_set_jip(brw, insn, br * (do_insn - insn));
 
-      brw_inst_set_exec_size(brw, insn, BRW_EXECUTE_8);
+      brw_inst_set_exec_size(brw, insn, p->compressed ? BRW_EXECUTE_16
+                                                      : BRW_EXECUTE_8);
    } else if (brw->gen == 6) {
       insn = next_insn(p, BRW_OPCODE_WHILE);
       do_insn = get_inner_do_insn(p);
@@ -1674,7 +1676,8 @@ brw_WHILE(struct brw_compile *p)
       brw_set_src0(p, insn, retype(brw_null_reg(), BRW_REGISTER_TYPE_D));
       brw_set_src1(p, insn, retype(brw_null_reg(), BRW_REGISTER_TYPE_D));
 
-      brw_inst_set_exec_size(brw, insn, BRW_EXECUTE_8);
+      brw_inst_set_exec_size(brw, insn, p->compressed ? BRW_EXECUTE_16
+                                                      : BRW_EXECUTE_8);
    } else {
       if (p->single_program_flow) {
 	 insn = next_insn(p, BRW_OPCODE_ADD);
-- 
2.0.2