From: Matt Turner Date: Tue, 3 May 2016 06:32:13 +0000 (-0700) Subject: i965/fs: Don't follow pow with an instruction with two dest regs. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=f01d92f4734a7ca62926dceda1d004c0cb10548c;p=mesa.git i965/fs: Don't follow pow with an instruction with two dest regs. Beginning with commit 7b208a73, Unigine Valley began hanging the GPU on Gen >= 8 platforms. Evidently that commit allowed the scheduler to make different choices that somehow finally ran afoul of a hardware bug in which POW and FDIV instructions may not be followed by an instruction with two destination registers (including compressed instructions). I presume the conditions are more complex than that, but the internal hardware bug report (BDWGFX bug_de 1696294) does not contain much more information. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94924 Reviewed-by: Topi Pohjolainen [v1] Tested-by: Mark Janes [v1] Reviewed-by: Francisco Jerez --- diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp index 8654ca4d0af..ff8d37e2c0c 100644 --- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp +++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp @@ -1726,6 +1726,24 @@ fs_generator::generate_code(const cfg_t *cfg, int dispatch_width) unsigned int last_insn_offset = p->next_insn_offset; bool multiple_instructions_emitted = false; + /* From the Broadwell PRM, Volume 7, "3D-Media-GPGPU", in the + * "Register Region Restrictions" section: for BDW, SKL: + * + * "A POW/FDIV operation must not be followed by an instruction + * that requires two destination registers." + * + * The documentation is often lacking annotations for Atom parts, + * and empirically this affects CHV as well. + */ + if (devinfo->gen >= 8 && + p->nr_insn > 1 && + brw_inst_opcode(devinfo, brw_last_inst) == BRW_OPCODE_MATH && + brw_inst_math_function(devinfo, brw_last_inst) == BRW_MATH_FUNCTION_POW && + inst->dst.component_size(inst->exec_size) > REG_SIZE) { + brw_NOP(p); + last_insn_offset = p->next_insn_offset; + } + if (unlikely(debug_flag)) annotate(p->devinfo, &annotation, cfg, inst, p->next_insn_offset);