From a50d2fdb4654984061bffb9293abb4178cbe435f Mon Sep 17 00:00:00 2001 From: Lionel Landwerlin Date: Mon, 23 Jan 2023 11:58:50 +0200 Subject: [PATCH] intel/fs: avoid cmod optimization on instruction with different write_mask MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit I've been running into failures with tests like : dEQP-VK.robustness.robustness2.bind.notemplate.rgba32i.unroll.nonvolatile.uniform_buffer_dynamic.no_fmt_qual.len_4.samples_1.1d.frag With the load_global_const_block_intel NIR intrinsic, you can load a vec8/vec16 with a predicate. The predicate is correctly uniformized to feed into the SEND instruction's flag register. The problem is that a series of optimization first remove the find_live_channel and then changes the broadcast into a simple MOV instruction, on the assumption that the first channel is always active if there is not control flow. This is correct. But after that the cmod optimzation will remove this instruction : mov.nz.f0.0(16) null:D, vgrf16+0.0<0>:D NoMask because it seems to be equivalent to : cmp.g.f0.0(16) vgrf16:D, vgrf12:D, 63d In this case vgrf16 is the predicate to the load block SEND instruction. Since the execution mask is different between both, some of the channels of the SEND instruction end up not being loaded or loaded with the wrong predication and we end up with incorrect UBO data. Signed-off-by: Lionel Landwerlin Cc: mesa-stable Reviewed-by: Marcin Ślusarz Reviewed-by: Ian Romanick Part-of: --- src/intel/compiler/brw_fs_cmod_propagation.cpp | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/intel/compiler/brw_fs_cmod_propagation.cpp b/src/intel/compiler/brw_fs_cmod_propagation.cpp index a439b2596ef..0fadb402172 100644 --- a/src/intel/compiler/brw_fs_cmod_propagation.cpp +++ b/src/intel/compiler/brw_fs_cmod_propagation.cpp @@ -303,6 +303,10 @@ opt_cmod_propagation_local(const intel_device_info *devinfo, bblock_t *block) scan_inst->exec_size != inst->exec_size) break; + /* If the write mask is different we can't propagate. */ + if (scan_inst->force_writemask_all != inst->force_writemask_all) + break; + /* CMP's result is the same regardless of dest type. */ if (inst->conditional_mod == BRW_CONDITIONAL_NZ && scan_inst->opcode == BRW_OPCODE_CMP &&