On 05/31/2018 10:37 PM, Timothy Arceri wrote: > This pass detects potential loop terminators and moves intructions > from the non breaking branch after the if. > > This enables both the new opt_if_simplification() pass and loop > unrolling to potentially progress further. > > Unexpectedly this change speed up shader-db run times by ~3% > > Ivy Bridge shader-db results (all changes in dolphin/ubershaders):
I was going to look at the changes in the generated code, but the smallest of these shaders is > 2300 instructions. Do you have any idea if any piglit or CTS tests hit this optimization path? One tiny nit below... > total instructions in shared programs: 9995662 -> 9995338 (-0.00%) > instructions in affected programs: 87845 -> 87521 (-0.37%) > helped: 27 > HURT: 0 > > total cycles in shared programs: 230931495 -> 230925015 (-0.00%) > cycles in affected programs: 56391385 -> 56384905 (-0.01%) > helped: 27 > HURT: 0 > --- > src/compiler/nir/nir_opt_if.c | 68 +++++++++++++++++++++++++++++++++++ > 1 file changed, 68 insertions(+) > > diff --git a/src/compiler/nir/nir_opt_if.c b/src/compiler/nir/nir_opt_if.c > index b03657a4244..1edeefdd5d1 100644 > --- a/src/compiler/nir/nir_opt_if.c > +++ b/src/compiler/nir/nir_opt_if.c > @@ -24,6 +24,7 @@ > #include "nir.h" > #include "nir/nir_builder.h" > #include "nir_control_flow.h" > +#include "nir_loop_analyze.h" > > /** > * This optimization detects if statements at the tops of loops where the > @@ -283,6 +284,72 @@ opt_if_simplification(nir_builder *b, nir_if *nif) > return true; > } > > +/** > + * This optimization simplifies potential loop terminators which then allows > + * other passes such as opt_if_simplification() and loop unrolling to > progress > + * further: > + * > + * if (cond) { > + * ... then block instructions ... > + * } else { > + * ... > + * break; > + * } > + * > + * into: > + * > + * if (cond) { > + * } else { > + * ... > + * break; > + * } > + * ... then block instructions ... > + */ > +static bool > +opt_if_loop_terminator(nir_if *nif) > +{ > + nir_block *break_blk = NULL; > + nir_block *continue_from_blk = NULL; > + bool continue_from_then = true; > + > + nir_block *last_then = nir_if_last_then_block(nif); > + nir_block *last_else = nir_if_last_else_block(nif); > + > + if (nir_block_ends_in_break(last_then)) { > + break_blk = last_then; > + continue_from_blk = last_else; > + continue_from_then = false; > + } else if (nir_block_ends_in_break(last_else)) { > + break_blk = last_else; > + continue_from_blk = last_then; > + } > + > + /* Continue if the if contained no jumps at all */ In prose, I like to use if-statement because I think it reads more easily. "Continue if the if-statement..." > + if (!break_blk) > + return false; > + > + /* If the continue from block is empty then return as there is nothing to > + * move. > + */ > + nir_block *first_continue_from_blk = continue_from_then ? > + nir_if_first_then_block(nif) : > + nir_if_first_else_block(nif); > + if (is_block_empty(first_continue_from_blk)) > + return false; > + > + if (!nir_is_trivial_loop_if(nif, break_blk)) > + return false; > + > + /* Finally, move the continue from branch after the if. */ > + nir_cf_list tmp; > + nir_cf_extract(&tmp, nir_before_block(first_continue_from_blk), > + nir_after_block(continue_from_blk)); > + nir_cf_reinsert(&tmp, nir_after_cf_node(&nif->cf_node)); > + nir_cf_delete(&tmp); > + > + return true; > +} > + > static bool > opt_if_cf_list(nir_builder *b, struct exec_list *cf_list) > { > @@ -296,6 +363,7 @@ opt_if_cf_list(nir_builder *b, struct exec_list *cf_list) > nir_if *nif = nir_cf_node_as_if(cf_node); > progress |= opt_if_cf_list(b, &nif->then_list); > progress |= opt_if_cf_list(b, &nif->else_list); > + progress |= opt_if_loop_terminator(nif); > progress |= opt_if_simplification(b, nif); > break; > } > _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev