Module: Mesa Branch: master Commit: 7aa76d66a1f5edad9e8c1d54aafdce99ffa6c345 URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=7aa76d66a1f5edad9e8c1d54aafdce99ffa6c345
Author: Francisco Jerez <[email protected]> Date: Fri May 27 00:45:04 2016 -0700 i965/fs: Skip SIMD lowering destination zipping if possible. Skipping the temporary allocation and copy instructions is easy (just return dst), but the conditions used to find out whether the copy can be optimized out safely without breaking the program are rather complex: The destination must be exactly one component of at most the execution width of the lowered instruction, and all source regions of the instruction must be either fully disjoint from the destination or be aligned with it group by group. v2: Don't handle partial source-destination overlap for simplicity (Jason). No instruction count regressions with respect to v1 in either shader-db or the few FP64 shader_runner test-cases with partial overlap I've checked manually. Cc: [email protected] Reviewed-by: Jason Ekstrand <[email protected]> --- src/mesa/drivers/dri/i965/brw_fs.cpp | 55 ++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp index 9abe73a..f8b0059 100644 --- a/src/mesa/drivers/dri/i965/brw_fs.cpp +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp @@ -5110,6 +5110,52 @@ emit_unzip(const fs_builder &lbld, bblock_t *block, fs_inst *inst, } /** + * Return true if splitting out the group of channels of instruction \p inst + * given by lbld.group() requires allocating a temporary for the destination + * of the lowered instruction and copying the data back to the original + * destination region. + */ +static inline bool +needs_dst_copy(const fs_builder &lbld, const fs_inst *inst) +{ + /* If the instruction writes more than one component we'll have to shuffle + * the results of multiple lowered instructions in order to make sure that + * they end up arranged correctly in the original destination region. + */ + if (inst->regs_written * REG_SIZE > + inst->dst.component_size(inst->exec_size)) + return true; + + /* If the lowered execution size is larger than the original the result of + * the instruction won't fit in the original destination, so we'll have to + * allocate a temporary in any case. + */ + if (lbld.dispatch_width() > inst->exec_size) + return true; + + for (unsigned i = 0; i < inst->sources; i++) { + /* If we already made a copy of the source for other reasons there won't + * be any overlap with the destination. + */ + if (needs_src_copy(lbld, inst, i)) + continue; + + /* In order to keep the logic simple we emit a copy whenever the + * destination region doesn't exactly match an overlapping source, which + * may point at the source and destination not being aligned group by + * group which could cause one of the lowered instructions to overwrite + * the data read from the same source by other lowered instructions. + */ + if (regions_overlap(inst->dst, inst->regs_written * REG_SIZE, + inst->src[i], inst->regs_read(i) * REG_SIZE) && + !inst->dst.equals(inst->src[i])) + return true; + } + + return false; +} + +/** * Insert data from a packed temporary into the channel group given by * lbld.group() of the destination region of instruction \p inst and return * the temporary as result. If any copy instructions are required they will @@ -5129,6 +5175,8 @@ emit_zip(const fs_builder &lbld, bblock_t *block, fs_inst *inst) const fs_reg dst = horiz_offset(inst->dst, lbld.group()); const unsigned dst_size = inst->regs_written * REG_SIZE / inst->dst.component_size(inst->exec_size); + + if (needs_dst_copy(lbld, inst)) { const fs_reg tmp = lbld.vgrf(inst->dst.type, dst_size); if (inst->predicate) { @@ -5146,6 +5194,13 @@ emit_zip(const fs_builder &lbld, bblock_t *block, fs_inst *inst) .MOV(offset(dst, inst->exec_size, k), offset(tmp, lbld, k)); return tmp; + + } else { + /* No need to allocate a temporary for the lowered instruction, just + * take the right group of channels from the original region. + */ + return dst; + } } bool _______________________________________________ mesa-commit mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/mesa-commit
