intel/fs: add 64 bit integer multiplication lowering

While NIR's lower_imul64() solves the case of 64 bit integer multiplications
generated early, we don't have a way to lower such instructions when they are
generated by our own backend, such as the scan/reduce intrinsics. We'll need
this soon, so implement it now.

An easy way to test this is to simply disable nir_lower_imul64 to let
those operations reach the backend.

v2:
  - Fix Q/UQ copy/paste errors (Caio).
  - Transform an 'if' into 'else if' (Caio).
  - Add an extra comment to clarify the need for 64b = 32b * 32b
    (Caio).
  - Make private functions private (Caio).
v3:
  - Remove ambiguity with 'b' and 'd' variables (Caio).
  - Allocate potentially less regs for the dwords (Caio).

Cc: Jason Ekstrand <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Caio Marcelo de Oliveira Filho <[email protected]>
Reviewed-by: Matt Turner <[email protected]>
Reviewed-by: Caio Marcelo de Oliveira Filho <[email protected]>
Signed-off-by: Paulo Zanoni <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/intel/compiler/brw_fs.h b/src/intel/compiler/brw_fs.h
index fb78fa829a0..a3604aef509 100644
--- a/src/intel/compiler/brw_fs.h
+++ b/src/intel/compiler/brw_fs.h
@@ -407,6 +407,7 @@ private:
    void resolve_inot_sources(const brw::fs_builder &bld, nir_alu_instr *instr,
                              fs_reg *op);
    void lower_mul_dword_inst(fs_inst *inst, bblock_t *block);
+   void lower_mul_qword_inst(fs_inst *inst, bblock_t *block);
    void lower_mulh_inst(fs_inst *inst, bblock_t *block);
 };