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authorCaio Marcelo de Oliveira Filho <[email protected]>2018-09-14 11:41:39 -0700
committerCaio Marcelo de Oliveira Filho <[email protected]>2018-10-15 17:29:46 -0700
commitb3c6146925595ec3a7eece3afb9ccaad32906d4c (patch)
treed0c815593ddab6912ce831f5b1b409d993feeb53 /bin
parentdc349f07b5f9c257f68ecf0cbb89f9722a42233a (diff)
nir: Copy propagation between blocks
Extend the pass to propagate the copies information along the control flow graph. It performs two walks, first it collects the vars that were written inside each node. Then it walks applying the copy propagation using a list of copies previously available. At each node the list is invalidated according to results from the first walk. This approach is simpler than a full data-flow analysis, but covers various cases. If derefs are used for operating on more memory resources (e.g. SSBOs), the difference from a regular pass is expected to be more visible -- as the SSA copy propagation pass won't apply to those. A full data-flow analysis would handle more scenarios: conditional breaks in the control flow and merge equivalent effects from multiple branches (e.g. using a phi node to merge the source for writes to the same deref). However, as previous commentary in the code stated, its complexity 'rapidly get out of hand'. The current patch is a good intermediate step towards more complex analysis. The 'copies' linked list was modified to use util_dynarray to make it more convenient to clone it (to handle ifs/loops). Annotated shader-db results for Skylake: total instructions in shared programs: 15105796 -> 15105451 (<.01%) instructions in affected programs: 152293 -> 151948 (-0.23%) helped: 96 HURT: 17 All the HURTs and many HELPs are one instruction. Looking at pass by pass outputs, the copy prop kicks in removing a bunch of loads correctly, which ends up altering what other other optimizations kick. In those cases the copies would be propagated after lowering to SSA. In few HELPs we are actually helping doing more than was possible previously, e.g. consolidating load_uniforms from different blocks. Most of those are from shaders/dolphin/ubershaders/. total cycles in shared programs: 566048861 -> 565954876 (-0.02%) cycles in affected programs: 151461830 -> 151367845 (-0.06%) helped: 2933 HURT: 2950 A lot of noise on both sides. total loops in shared programs: 4603 -> 4603 (0.00%) loops in affected programs: 0 -> 0 helped: 0 HURT: 0 total spills in shared programs: 11085 -> 11073 (-0.11%) spills in affected programs: 23 -> 11 (-52.17%) helped: 1 HURT: 0 The shaders/dolphin/ubershaders/12.shader_test was able to pull a couple of loads from inside if statements and reuse them. total fills in shared programs: 23143 -> 23089 (-0.23%) fills in affected programs: 2718 -> 2664 (-1.99%) helped: 27 HURT: 0 All from shaders/dolphin/ubershaders/. LOST: 0 GAINED: 0 The other generations follow the same overall shape. The spills and fills HURTs are all from the same game. shader-db results for Broadwell. total instructions in shared programs: 15402037 -> 15401841 (<.01%) instructions in affected programs: 144386 -> 144190 (-0.14%) helped: 86 HURT: 9 total cycles in shared programs: 600912755 -> 600902486 (<.01%) cycles in affected programs: 185662820 -> 185652551 (<.01%) helped: 2598 HURT: 3053 total loops in shared programs: 4579 -> 4579 (0.00%) loops in affected programs: 0 -> 0 helped: 0 HURT: 0 total spills in shared programs: 80929 -> 80924 (<.01%) spills in affected programs: 720 -> 715 (-0.69%) helped: 1 HURT: 5 total fills in shared programs: 93057 -> 93013 (-0.05%) fills in affected programs: 3398 -> 3354 (-1.29%) helped: 27 HURT: 5 LOST: 0 GAINED: 2 shader-db results for Haswell: total instructions in shared programs: 9231975 -> 9230357 (-0.02%) instructions in affected programs: 44992 -> 43374 (-3.60%) helped: 27 HURT: 69 total cycles in shared programs: 87760587 -> 87727502 (-0.04%) cycles in affected programs: 7720673 -> 7687588 (-0.43%) helped: 1609 HURT: 1416 total loops in shared programs: 1830 -> 1830 (0.00%) loops in affected programs: 0 -> 0 helped: 0 HURT: 0 total spills in shared programs: 1988 -> 1692 (-14.89%) spills in affected programs: 296 -> 0 helped: 1 HURT: 0 total fills in shared programs: 2103 -> 1668 (-20.68%) fills in affected programs: 438 -> 3 (-99.32%) helped: 4 HURT: 0 LOST: 0 GAINED: 1 v2: Remove the DISABLE prefix from tests we now pass. v3: Add comments about missing write_mask handling. (Caio) Add unreachable when switching on cf_node type. (Jason) Properly merge the component information in written map instead of replacing. (Jason) Explain how removal from written arrays works. (Jason) Use mode directly from deref instead of getting the var. (Jason) v4: Register the local written mode for calls. (Jason) Prefer cf_node instead of node. (Jason) Clarify that remove inside iteration only works in backward iterations. (Jason) Reviewed-by: Jason Ekstrand <[email protected]>
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