ScheduleOptimizer: Rewrite getPrevectorMap to use isl_pw_aff
This increases the readablity. This also adds some comments that explain what this function does. llvm-svn: 146028
This commit is contained in:
Tobias Grosser
parent
4a8e356f36
commit
2493e92530
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@ -26,6 +26,7 @@
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#include "polly/Dependences.h"
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#include "polly/ScopInfo.h"
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#include "isl/aff.h"
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#include "isl/space.h"
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#include "isl/map.h"
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#include "isl/constraint.h"
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@ -223,68 +224,107 @@ isl_union_map *getScheduleForBand(isl_band *Band) {
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return isl_union_map_apply_range(PartialSchedule, TileUMap);
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}
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static isl_map *getPrevectorMap(isl_ctx *ctx, int vectorDimension,
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int scheduleDimensions,
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int parameterDimensions,
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int vectorWidth = 4) {
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assert (0 <= vectorDimension && vectorDimension < scheduleDimensions);
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isl_space *Space = isl_space_alloc(ctx, parameterDimensions,
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scheduleDimensions, scheduleDimensions + 2);
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isl_basic_map *tilingMap = isl_basic_map_universe(isl_space_copy(Space));
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// Create a map that pre-vectorizes one scheduling dimension.
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//
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// getPrevectorMap creates a map that maps each input dimension to the same
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// output dimension, except for the dimension DimToVectorize. DimToVectorize is
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// strip mined by 'VectorWidth' and the newly created point loop of
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// DimToVectorize is moved to the innermost level.
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//
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// Example (DimToVectorize=0, ScheduleDimensions=2, VectorWidth=4):
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//
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// | Before transformation
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// |
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// | A[i,j] -> [i,j]
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// |
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// | for (i = 0; i < 128; i++)
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// | for (j = 0; j < 128; j++)
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// | A(i,j);
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//
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// Prevector map:
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// [i,j] -> [it,j,ip] : it % 4 = 0 and it <= ip <= it + 3 and i = ip
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//
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// | After transformation:
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// |
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// | A[i,j] -> [it,j,ip] : it % 4 = 0 and it <= ip <= it + 3 and i = ip
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// |
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// | for (it = 0; it < 128; it+=4)
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// | for (j = 0; j < 128; j++)
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// | for (ip = max(0,it); ip < min(128, it + 3); ip++)
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// | A(ip,j);
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//
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// The goal of this transformation is to create a trivially vectorizable loop.
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// This means a parallel loop at the innermost level that has a constant number
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// of iterations corresponding to the target vector width.
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//
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// This transformation creates a loop at the innermost level. The loop has a
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// constant number of iterations, if the number of loop iterations at
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// DimToVectorize can be devided by VectorWidth. The default VectorWidth is
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// currently constant and not yet target specific. This function does not reason
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// about parallelism.
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static isl_map *getPrevectorMap(isl_ctx *ctx, int DimToVectorize,
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int ScheduleDimensions,
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int VectorWidth = 4) {
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isl_space *Space;
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isl_local_space *LocalSpace, *LocalSpaceRange;
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isl_set *Modulo;
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isl_map *TilingMap;
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isl_constraint *c;
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isl_aff *Aff;
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int PointDimension; /* ip */
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int TileDimension; /* it */
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isl_int VectorWidthMP;
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isl_local_space *LocalSpace = isl_local_space_from_space(Space);
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assert (0 <= DimToVectorize && DimToVectorize < ScheduleDimensions);
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for (int i = 0; i < vectorDimension; i++) {
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Space = isl_space_alloc(ctx, 0, ScheduleDimensions, ScheduleDimensions + 1);
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TilingMap = isl_map_universe(isl_space_copy(Space));
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LocalSpace = isl_local_space_from_space(Space);
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PointDimension = ScheduleDimensions;
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TileDimension = DimToVectorize;
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// Create an identity map for everything except DimToVectorize and map
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// DimToVectorize to the point loop at the innermost dimension.
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for (int i = 0; i < ScheduleDimensions; i++) {
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c = isl_equality_alloc(isl_local_space_copy(LocalSpace));
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isl_constraint_set_coefficient_si(c, isl_dim_in, i, -1);
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isl_constraint_set_coefficient_si(c, isl_dim_out, i, 1);
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tilingMap = isl_basic_map_add_constraint(tilingMap, c);
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if (i == DimToVectorize)
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isl_constraint_set_coefficient_si(c, isl_dim_out, PointDimension, 1);
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else
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isl_constraint_set_coefficient_si(c, isl_dim_out, i, 1);
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TilingMap = isl_map_add_constraint(TilingMap, c);
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}
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for (int i = vectorDimension + 1; i < scheduleDimensions; i++) {
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c = isl_equality_alloc(isl_local_space_copy(LocalSpace));
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isl_constraint_set_coefficient_si(c, isl_dim_in, i, -1);
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isl_constraint_set_coefficient_si(c, isl_dim_out, i, 1);
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tilingMap = isl_basic_map_add_constraint(tilingMap, c);
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}
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int stepDimension = scheduleDimensions;
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int auxilaryDimension = scheduleDimensions + 1;
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c = isl_equality_alloc(isl_local_space_copy(LocalSpace));
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isl_constraint_set_coefficient_si(c, isl_dim_out, vectorDimension, 1);
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isl_constraint_set_coefficient_si(c, isl_dim_out, auxilaryDimension,
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-vectorWidth);
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tilingMap = isl_basic_map_add_constraint(tilingMap, c);
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c = isl_equality_alloc(isl_local_space_copy(LocalSpace));
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isl_constraint_set_coefficient_si(c, isl_dim_in, vectorDimension, -1);
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isl_constraint_set_coefficient_si(c, isl_dim_out, stepDimension, 1);
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tilingMap = isl_basic_map_add_constraint(tilingMap, c);
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// it % 'VectorWidth' = 0
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LocalSpaceRange = isl_local_space_range(isl_local_space_copy(LocalSpace));
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Aff = isl_aff_zero_on_domain(LocalSpaceRange);
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Aff = isl_aff_set_constant_si(Aff, VectorWidth);
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Aff = isl_aff_set_coefficient_si(Aff, isl_dim_in, TileDimension, 1);
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isl_int_init(VectorWidthMP);
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isl_int_set_si(VectorWidthMP, VectorWidth);
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Aff = isl_aff_mod(Aff, VectorWidthMP);
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isl_int_clear(VectorWidthMP);
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Modulo = isl_pw_aff_zero_set(isl_pw_aff_from_aff(Aff));
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TilingMap = isl_map_intersect_range(TilingMap, Modulo);
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// it <= ip
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c = isl_inequality_alloc(isl_local_space_copy(LocalSpace));
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isl_constraint_set_coefficient_si(c, isl_dim_out, vectorDimension, -1);
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isl_constraint_set_coefficient_si(c, isl_dim_out, stepDimension, 1);
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tilingMap = isl_basic_map_add_constraint(tilingMap, c);
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isl_constraint_set_coefficient_si(c, isl_dim_out, TileDimension, -1);
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isl_constraint_set_coefficient_si(c, isl_dim_out, PointDimension, 1);
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TilingMap = isl_map_add_constraint(TilingMap, c);
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// ip <= it + ('VectorWidth' - 1)
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c = isl_inequality_alloc(LocalSpace);
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isl_constraint_set_coefficient_si(c, isl_dim_out, vectorDimension, 1);
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isl_constraint_set_coefficient_si(c, isl_dim_out, stepDimension, -1);
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isl_constraint_set_constant_si(c, vectorWidth- 1);
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tilingMap = isl_basic_map_add_constraint(tilingMap, c);
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isl_constraint_set_coefficient_si(c, isl_dim_out, TileDimension, 1);
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isl_constraint_set_coefficient_si(c, isl_dim_out, PointDimension, -1);
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isl_constraint_set_constant_si(c, VectorWidth - 1);
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TilingMap = isl_map_add_constraint(TilingMap, c);
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// Project out auxilary dimensions (introduced to ensure 'ii % tileSize = 0')
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//
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// The real dimensions are transformed into existentially quantified ones.
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// This reduces the number of visible scattering dimensions. Also, Cloog
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// produces better code, if auxilary dimensions are existentially quantified.
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tilingMap = isl_basic_map_project_out(tilingMap, isl_dim_out,
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scheduleDimensions + 1, 1);
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isl_map_dump(TilingMap);
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return isl_map_from_basic_map(tilingMap);
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return TilingMap;
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}
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// getScheduleForBandList - Get the scheduling map for a list of bands.
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@ -328,7 +368,7 @@ static isl_union_map *getScheduleForBandList(isl_band_list *BandList) {
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isl_union_map *TileUMap;
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TileMap = getPrevectorMap(ctx, ScheduleDimensions + i,
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ScheduleDimensions * 2, 0);
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ScheduleDimensions * 2);
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TileUMap = isl_union_map_from_map(TileMap);
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TileUMap = isl_union_map_align_params(TileUMap,
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isl_space_copy(Space));
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