[Mesa-dev] [PATCH 12/21] etnaviv: compiler: generate instructions for log2

[Philipp Zabel]

From: Michael Tretter <m.tretter at pengutronix.de>

flog2 is implemented as 2 instructions in the Vivante machine code. The
log calculates x and y, which have to be multiplied to get the actual
log result.

We need to allocate a temporary register for this, which will fail if to
many flog2 instructions are used (e.g. in the glmark2 ideas benchmark).

TODO: move this up into NIR as a lowering step.

Signed-off-by: Michael Tretter <m.tretter at pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>
---
 src/gallium/drivers/etnaviv/etnaviv_compiler.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/gallium/drivers/etnaviv/etnaviv_compiler.c b/src/gallium/drivers/etnaviv/etnaviv_compiler.c
index 129c9115e783..66553199fe19 100644
--- a/src/gallium/drivers/etnaviv/etnaviv_compiler.c
+++ b/src/gallium/drivers/etnaviv/etnaviv_compiler.c
@@ -2101,6 +2101,24 @@ etna_emit_alu(struct etna_compile *c, nir_alu_instr *instr)
          .src[2] = src[0],
       });
       break;
+   case nir_op_flog2:
+      {
+      struct etna_native_reg temp = etna_compile_get_inner_temp(c); /* only using .xy */
+      emit_inst(c, &(struct etna_inst) {
+         .opcode = INST_OPCODE_LOG,
+         .sat = 0,
+         .dst = etna_native_to_dst(temp, INST_COMPS_X | INST_COMPS_Y),
+         .src[2] = src[0],
+         .tex = { .amode=1 }, /* Unknown bit needs to be set */
+      });
+      emit_inst(c, &(struct etna_inst) {
+         .opcode = INST_OPCODE_MUL,
+         .dst = dst,
+         .src[0] = etna_native_to_src(temp, SWIZZLE(X, X, X, X)),
+         .src[1] = etna_native_to_src(temp, SWIZZLE(Y, Y, Y, Y)),
+      });
+      }
+      break;
    case nir_op_fexp2:
       emit_inst(c, &(struct etna_inst) {
          .opcode = INST_OPCODE_EXP,
-- 
2.17.1