[mlir] Use affine dim instead of symbol in SCFToGPU lowering.

[tpopp]

Summary

This still satisfies the constraints required by the affine dialect and
gives more flexibility in what iteration bounds can be used when
loewring to the GPU dialect.

[herhut]

Thanks!

mlir/lib/Conversion/SCFToGPU/SCFToGPU.cpp

if (isMappedToProcessor(processor)) {
               return parallelOp.emitOpError()
                      << "cannot derive loop-invariant upper bound for number "
                         "of iterations";
             }
           }
           // Compute the number of iterations needed. We compute this as an
           // affine expression ceilDiv (upperBound - lowerBound) step. We use
           // affine.apply here so that it composes nicely with the provided map.
-          AffineMap stepMap =
-              AffineMap::get(0, 3,
-                             ((rewriter.getAffineSymbolExpr(0) -
-                               rewriter.getAffineSymbolExpr(1))
-                                  .ceilDiv(rewriter.getAffineSymbolExpr(2))));
+          AffineMap stepMap = AffineMap::get(
+              1, 2,
+              ((rewriter.getAffineDimExpr(0) - rewriter.getAffineSymbolExpr(0))
+                   .ceilDiv(rewriter.getAffineSymbolExpr(1))));
           Value launchBound = rewriter.create<AffineApplyOp>(
               loc, annotation.bound().getValue().compose(stepMap),
               ValueRange{
                   ensureLaunchIndependent(
                       cloningMap.lookupOrDefault(upperBound)),
                   ensureLaunchIndependent(
                       cloningMap.lookupOrDefault(lowerBound)),
                   ensureLaunchIndependent(cloningMap.lookupOrDefault(step))});

mlir/test/Conversion/SCFToGPU/parallel_loop.mlir

func @parallel_loop_bidy_bidx(%arg0 : index, %arg1 : index, %arg2 : index,
   scf.parallel (%i0, %i1) = (%arg0, %arg1) to (%arg2, %arg3)
                                           step (%arg4, %step)  {
     %val = load %buf[%i0, %i1] : memref<?x?xf32>
     store %val, %res[%i1, %i0] : memref<?x?xf32>
   } { mapping = [{processor = 1, map = affine_map<(d0) -> (d0)>, bound = affine_map<(d0) -> (d0)>}, {processor = 0, map = affine_map<(d0) -> (d0)>, bound = affine_map<(d0) -> (d0)>}] }
   return
 }
 
-// CHECK:       #[[$MAP0:.*]] = affine_map<()[s0, s1, s2] -> ((s0 - s1) ceildiv s2)>
+// CHECK:       #[[$MAP0:.*]] = affine_map<(d0)[s0, s1] -> ((d0 - s0) ceildiv s1)>
 // CHECK:       #[[$MAP1:.*]] = affine_map<(d0)[s0, s1] -> (d0 * s0 + s1)>
 
 // CHECK:       module {
 // CHECK-LABEL:   func @parallel_loop_bidy_bidx(
 // CHECK-SAME:                                  [[VAL_0:%.*]]: index, [[VAL_1:%.*]]: index, [[VAL_2:%.*]]: index, [[VAL_3:%.*]]: index, [[VAL_4:%.*]]: index, [[VAL_5:%.*]]: memref<?x?xf32>, [[VAL_6:%.*]]: memref<?x?xf32>) {
 // CHECK:           [[VAL_7:%.*]] = constant 2 : index
 // CHECK:           [[VAL_8:%.*]] = constant 1 : index
-// CHECK:           [[VAL_9:%.*]] = affine.apply #[[$MAP0]](){{\[}}[[VAL_2]], [[VAL_0]], [[VAL_4]]]
-// CHECK:           [[VAL_10:%.*]] = affine.apply #[[$MAP0]](){{\[}}[[VAL_3]], [[VAL_1]], [[VAL_7]]]
+// CHECK:           [[VAL_9:%.*]] = affine.apply #[[$MAP0]]([[VAL_2]]){{\[}}[[VAL_0]], [[VAL_4]]]
+// CHECK:           [[VAL_10:%.*]] = affine.apply #[[$MAP0]]([[VAL_3]]){{\[}}[[VAL_1]], [[VAL_7]]]
 // CHECK:           gpu.launch blocks([[VAL_11:%.*]], [[VAL_12:%.*]], [[VAL_13:%.*]]) in ([[VAL_14:%.*]] = [[VAL_10]], [[VAL_15:%.*]] = [[VAL_9]], [[VAL_16:%.*]] = [[VAL_8]]) threads([[VAL_17:%.*]], [[VAL_18:%.*]], [[VAL_19:%.*]]) in ([[VAL_20:%.*]] = [[VAL_8]], [[VAL_21:%.*]] = [[VAL_8]], [[VAL_22:%.*]] = [[VAL_8]]) {
 // CHECK:             [[VAL_23:%.*]] = affine.apply #[[$MAP1]]([[VAL_12]]){{\[}}[[VAL_4]], [[VAL_0]]]
 // CHECK:             [[VAL_24:%.*]] = affine.apply #[[$MAP1]]([[VAL_11]]){{\[}}[[VAL_7]], [[VAL_1]]]
 // CHECK:             [[VAL_25:%.*]] = load [[VAL_5]]{{\[}}[[VAL_23]], [[VAL_24]]] : memref<?x?xf32>
 // CHECK:             store [[VAL_25]], [[VAL_6]]{{\[}}[[VAL_24]], [[VAL_23]]] : memref<?x?xf32>
 // CHECK:             gpu.terminator
 // CHECK:           }
 // CHECK:           return
scf.parallel (%i0, %i1) = (%arg0, %arg1) to (%arg2, %arg3)
      ] }
   } { mapping = [
       {processor = 1, map = affine_map<(d0) -> (d0)>, bound = affine_map<(d0) -> (d0)>},
       {processor = 0, map = affine_map<(d0) -> (d0)>, bound = affine_map<(d0) -> (d0)>}
     ] }
   return
 }
 
-// CHECK:       #[[$MAP0:.*]] = affine_map<()[s0, s1, s2] -> ((s0 - s1) ceildiv s2)>
+// CHECK:       #[[$MAP0:.*]] = affine_map<(d0)[s0, s1] -> ((d0 - s0) ceildiv s1)>
 // CHECK:       #[[$MAP1:.*]] = affine_map<(d0)[s0, s1] -> (d0 * s0 + s1)>
 
 // CHECK:       module {
 // CHECK-LABEL:   func @parallel_loop_tiled(
 // CHECK-SAME:                              [[VAL_26:%.*]]: index, [[VAL_27:%.*]]: index, [[VAL_28:%.*]]: index, [[VAL_29:%.*]]: index, [[VAL_30:%.*]]: memref<?x?xf32>, [[VAL_31:%.*]]: memref<?x?xf32>) {
 // CHECK:           [[VAL_32:%.*]] = constant 0 : index
 // CHECK:           [[VAL_33:%.*]] = constant 1 : index
 // CHECK:           [[VAL_34:%.*]] = constant 4 : index
 // CHECK:           [[VAL_35:%.*]] = constant 1 : index
-// CHECK:           [[VAL_36:%.*]] = affine.apply #[[$MAP0]](){{\[}}[[VAL_28]], [[VAL_26]], [[VAL_34]]]
-// CHECK:           [[VAL_37:%.*]] = affine.apply #[[$MAP0]](){{\[}}[[VAL_29]], [[VAL_27]], [[VAL_34]]]
-// CHECK:           [[VAL_38:%.*]] = affine.apply #[[$MAP0]](){{\[}}[[VAL_34]], [[VAL_32]], [[VAL_33]]]
-// CHECK:           [[VAL_39:%.*]] = affine.apply #[[$MAP0]](){{\[}}[[VAL_34]], [[VAL_32]], [[VAL_33]]]
+// CHECK:           [[VAL_36:%.*]] = affine.apply #[[$MAP0]]([[VAL_28]]){{\[}}[[VAL_26]], [[VAL_34]]]
+// CHECK:           [[VAL_37:%.*]] = affine.apply #[[$MAP0]]([[VAL_29]]){{\[}}[[VAL_27]], [[VAL_34]]]
+// CHECK:           [[VAL_38:%.*]] = affine.apply #[[$MAP0]]([[VAL_34]]){{\[}}[[VAL_32]], [[VAL_33]]]
+// CHECK:           [[VAL_39:%.*]] = affine.apply #[[$MAP0]]([[VAL_34]]){{\[}}[[VAL_32]], [[VAL_33]]]
 // CHECK:           gpu.launch blocks([[VAL_40:%.*]], [[VAL_41:%.*]], [[VAL_42:%.*]]) in ([[VAL_43:%.*]] = [[VAL_37]], [[VAL_44:%.*]] = [[VAL_36]], [[VAL_45:%.*]] = [[VAL_35]]) threads([[VAL_46:%.*]], [[VAL_47:%.*]], [[VAL_48:%.*]]) in ([[VAL_49:%.*]] = [[VAL_39]], [[VAL_50:%.*]] = [[VAL_38]], [[VAL_51:%.*]] = [[VAL_35]]) {
 // CHECK:             [[VAL_52:%.*]] = affine.apply #[[$MAP1]]([[VAL_41]]){{\[}}[[VAL_34]], [[VAL_26]]]
 // CHECK:             [[VAL_53:%.*]] = affine.apply #[[$MAP1]]([[VAL_40]]){{\[}}[[VAL_34]], [[VAL_27]]]
 // CHECK:             [[VAL_54:%.*]] = affine.apply #[[$MAP1]]([[VAL_47]]){{\[}}[[VAL_33]], [[VAL_32]]]
 // CHECK:             [[VAL_55:%.*]] = affine.apply #[[$MAP1]]([[VAL_46]]){{\[}}[[VAL_33]], [[VAL_32]]]
 // CHECK:             [[VAL_56:%.*]] = addi [[VAL_52]], [[VAL_54]] : index
 // CHECK:             [[VAL_57:%.*]] = addi [[VAL_53]], [[VAL_55]] : index
 // CHECK:             [[VAL_58:%.*]] = load [[VAL_30]]{{\[}}[[VAL_56]], [[VAL_57]]] : memref<?x?xf32>
scf.parallel (%i0, %i1) = (%arg0, %arg1) to (%arg2, %arg3)
     store %val, %res[%i1, %i0] : memref<?x?xf32>
   } { mapping = [
       {processor = 1, map = affine_map<(d0) -> (d0)>, bound = affine_map<(d0) -> (d0)>},
       {processor = 6, map = affine_map<(d0) -> (d0)>, bound = affine_map<(d0) -> (d0)>}
     ] }
   return
 }
 
-// CHECK:       #[[$MAP0:.*]] = affine_map<()[s0, s1, s2] -> ((s0 - s1) ceildiv s2)>
+// CHECK:       #[[$MAP0:.*]] = affine_map<(d0)[s0, s1] -> ((d0 - s0) ceildiv s1)>
 // CHECK:       #[[$MAP1:.*]] = affine_map<(d0)[s0, s1] -> (d0 * s0 + s1)>
 
 // CHECK:       module {
 // CHECK-LABEL:   func @parallel_loop_bidy_seq(
 // CHECK-SAME:                                 [[VAL_59:%.*]]: index, [[VAL_60:%.*]]: index, [[VAL_61:%.*]]: index, [[VAL_62:%.*]]: index, [[VAL_63:%.*]]: index, [[VAL_64:%.*]]: memref<?x?xf32>, [[VAL_65:%.*]]: memref<?x?xf32>) {
 // CHECK:           [[VAL_66:%.*]] = constant 2 : index
 // CHECK:           [[VAL_67:%.*]] = constant 1 : index
-// CHECK:           [[VAL_68:%.*]] = affine.apply #[[$MAP0]](){{\[}}[[VAL_61]], [[VAL_59]], [[VAL_63]]]
+// CHECK:           [[VAL_68:%.*]] = affine.apply #[[$MAP0]]([[VAL_61]]){{\[}}[[VAL_59]], [[VAL_63]]]
 // CHECK:           gpu.launch blocks([[VAL_69:%.*]], [[VAL_70:%.*]], [[VAL_71:%.*]]) in ([[VAL_72:%.*]] = [[VAL_67]], [[VAL_73:%.*]] = [[VAL_68]], [[VAL_74:%.*]] = [[VAL_67]]) threads([[VAL_75:%.*]], [[VAL_76:%.*]], [[VAL_77:%.*]]) in ([[VAL_78:%.*]] = [[VAL_67]], [[VAL_79:%.*]] = [[VAL_67]], [[VAL_80:%.*]] = [[VAL_67]]) {
 // CHECK:             [[VAL_81:%.*]] = affine.apply #[[$MAP1]]([[VAL_70]]){{\[}}[[VAL_63]], [[VAL_59]]]
 // CHECK:             scf.for [[VAL_82:%.*]] = [[VAL_60]] to [[VAL_62]] step [[VAL_66]] {
 // CHECK:               [[VAL_83:%.*]] = load [[VAL_64]]{{\[}}[[VAL_81]], [[VAL_82]]] : memref<?x?xf32>
 // CHECK:               store [[VAL_83]], [[VAL_65]]{{\[}}[[VAL_82]], [[VAL_81]]] : memref<?x?xf32>
 // CHECK:             }
 // CHECK:             gpu.terminator
 // CHECK:           }
scf.parallel (%si0, %si1) = (%zero, %zero) to (%four, %four)
       ] }
   } { mapping = [
       {processor = 1, map = affine_map<(d0) -> (d0)>, bound = affine_map<(d0) -> (d0)>},
       {processor = 6, map = affine_map<(d0) -> (d0)>, bound = affine_map<(d0) -> (d0)>}
     ] }
   return
 }
 
-// CHECK:       #[[$MAP0:.*]] = affine_map<()[s0, s1, s2] -> ((s0 - s1) ceildiv s2)>
+// CHECK:       #[[$MAP0:.*]] = affine_map<(d0)[s0, s1] -> ((d0 - s0) ceildiv s1)>
 // CHECK:       #[[$MAP1:.*]] = affine_map<(d0)[s0, s1] -> (d0 * s0 + s1)>
 
 // CHECK:       module {
 // CHECK-LABEL:   func @parallel_loop_tiled_seq(
 // CHECK-SAME:                                  [[VAL_84:%.*]]: index, [[VAL_85:%.*]]: index, [[VAL_86:%.*]]: index, [[VAL_87:%.*]]: index, [[VAL_88:%.*]]: memref<?x?xf32>, [[VAL_89:%.*]]: memref<?x?xf32>) {
 // CHECK:           [[VAL_90:%.*]] = constant 0 : index
 // CHECK:           [[VAL_91:%.*]] = constant 1 : index
 // CHECK:           [[VAL_92:%.*]] = constant 4 : index
 // CHECK:           [[VAL_93:%.*]] = constant 1 : index
-// CHECK:           [[VAL_94:%.*]] = affine.apply #[[$MAP0]](){{\[}}[[VAL_86]], [[VAL_84]], [[VAL_92]]]
-// CHECK:           [[VAL_95:%.*]] = affine.apply #[[$MAP0]](){{\[}}[[VAL_92]], [[VAL_90]], [[VAL_91]]]
+// CHECK:           [[VAL_94:%.*]] = affine.apply #[[$MAP0]]([[VAL_86]]){{\[}}[[VAL_84]], [[VAL_92]]]
+// CHECK:           [[VAL_95:%.*]] = affine.apply #[[$MAP0]]([[VAL_92]]){{\[}}[[VAL_90]], [[VAL_91]]]
 // CHECK:           gpu.launch blocks([[VAL_96:%.*]], [[VAL_97:%.*]], [[VAL_98:%.*]]) in ([[VAL_99:%.*]] = [[VAL_93]], [[VAL_100:%.*]] = [[VAL_94]], [[VAL_101:%.*]] = [[VAL_93]]) threads([[VAL_102:%.*]], [[VAL_103:%.*]], [[VAL_104:%.*]]) in ([[VAL_105:%.*]] = [[VAL_93]], [[VAL_106:%.*]] = [[VAL_95]], [[VAL_107:%.*]] = [[VAL_93]]) {
 // CHECK:             [[VAL_108:%.*]] = affine.apply #[[$MAP1]]([[VAL_97]]){{\[}}[[VAL_92]], [[VAL_84]]]
 // CHECK:             scf.for [[VAL_109:%.*]] = [[VAL_85]] to [[VAL_87]] step [[VAL_92]] {
 // CHECK:               [[VAL_110:%.*]] = affine.apply #[[$MAP1]]([[VAL_103]]){{\[}}[[VAL_91]], [[VAL_90]]]
 // CHECK:               scf.for [[VAL_111:%.*]] = [[VAL_90]] to [[VAL_92]] step [[VAL_91]] {
 // CHECK:                 [[VAL_112:%.*]] = addi [[VAL_108]], [[VAL_110]] : index
 // CHECK:                 [[VAL_113:%.*]] = addi [[VAL_109]], [[VAL_111]] : index
 // CHECK:                 [[VAL_114:%.*]] = load [[VAL_88]]{{\[}}[[VAL_112]], [[VAL_113]]] : memref<?x?xf32>
scf.parallel (%arg3, %arg4) = (%c0, %c0) to (%0, %1) step (%c2, %c3) {
       } {mapping = [{bound = affine_map<(d0) -> (d0)>, map = affine_map<(d0) -> (d0)>, processor = 3 : i64}, {bound = affine_map<(d0) -> (d0)>, map = affine_map<(d0) -> (d0)>, processor = 4 : i64}]}
       scf.yield
     } {mapping = [{bound = affine_map<(d0) -> (d0)>, map = affine_map<(d0) -> (d0)>, processor = 0 : i64}, {bound = affine_map<(d0) -> (d0)>, map = affine_map<(d0) -> (d0)>, processor = 1 : i64}]}
     return
   }
 }
 
 // CHECK:       #[[$MAP0:.*]] = affine_map<(d0, d1)[s0, s1] -> (d0 * s1 + s0 + d1)>
-// CHECK:       #[[$MAP1:.*]] = affine_map<()[s0, s1, s2] -> ((s0 - s1) ceildiv s2)>
+// CHECK:       #[[$MAP1:.*]] = affine_map<(d0)[s0, s1] -> ((d0 - s0) ceildiv s1)>
 // CHECK:       #[[$MAP2:.*]] = affine_map<(d0)[s0, s1] -> (d0 * s0 + s1)>
 // CHECK:       #[[$MAP3:.*]] = affine_map<(d0)[s0] -> (2, -d0 + s0)>
 // CHECK:       #[[$MAP4:.*]] = affine_map<(d0)[s0] -> (3, -d0 + s0)>
 // CHECK:       #[[$MAP5:.*]] = affine_map<(d0, d1)[s0, s1, s2] -> (d0 * s1 + s0 + d1 * s2)>
 
 // CHECK:       module {
 // CHECK-LABEL:   func @sum(
 // CHECK-SAME:              [[VAL_0:%.*]]: memref<?x?xf32, #[[$MAP0]]>, [[VAL_1:%.*]]: memref<?x?xf32, #[[$MAP0]]>, [[VAL_2:%.*]]: memref<?x?xf32, #[[$MAP0]]>) {
 // CHECK:           %[[C1:.*]] = constant 1 : index
 // CHECK:           %[[C0:.*]] = constant 0 : index
 // CHECK:           %[[C3:.*]] = constant 3 : index
 // CHECK:           %[[C2:.*]] = constant 2 : index
 // CHECK:           [[VAL_7:%.*]] = dim [[VAL_0]], %[[C0]] : memref<?x?xf32, #[[$MAP0]]>
 // CHECK:           [[VAL_8:%.*]] = dim [[VAL_0]], %[[C1]] : memref<?x?xf32, #[[$MAP0]]>
 // CHECK:           [[VAL_9:%.*]] = constant 1 : index
-// CHECK:           [[VAL_10:%.*]] = affine.apply #[[$MAP1]](){{\[}}[[VAL_7]], %[[C0]], %[[C2]]]
-// CHECK:           [[VAL_11:%.*]] = affine.apply #[[$MAP1]](){{\[}}[[VAL_8]], %[[C0]], %[[C3]]]
+// CHECK:           [[VAL_10:%.*]] = affine.apply #[[$MAP1]]([[VAL_7]]){{\[}}%[[C0]], %[[C2]]]
+// CHECK:           [[VAL_11:%.*]] = affine.apply #[[$MAP1]]([[VAL_8]]){{\[}}%[[C0]], %[[C3]]]
 // CHECK:           [[VAL_12:%.*]] = constant 4 : index
-// CHECK:           [[VAL_13:%.*]] = affine.apply #[[$MAP1]](){{\[}}[[VAL_12]], %[[C0]], %[[C1]]]
+// CHECK:           [[VAL_13:%.*]] = affine.apply #[[$MAP1]]([[VAL_12]]){{\[}}%[[C0]], %[[C1]]]
 // CHECK:           [[VAL_14:%.*]] = constant 3 : index
-// CHECK:           [[VAL_15:%.*]] = affine.apply #[[$MAP1]](){{\[}}[[VAL_14]], %[[C0]], %[[C1]]]
+// CHECK:           [[VAL_15:%.*]] = affine.apply #[[$MAP1]]([[VAL_14]]){{\[}}%[[C0]], %[[C1]]]
 // CHECK:           gpu.launch blocks([[VAL_16:%.*]], [[VAL_17:%.*]], [[VAL_18:%.*]]) in ([[VAL_19:%.*]] = [[VAL_10]], [[VAL_20:%.*]] = [[VAL_11]], [[VAL_21:%.*]] = [[VAL_9]]) threads([[VAL_22:%.*]], [[VAL_23:%.*]], [[VAL_24:%.*]]) in ([[VAL_25:%.*]] = [[VAL_13]], [[VAL_26:%.*]] = [[VAL_15]], [[VAL_27:%.*]] = [[VAL_9]]) {
 // CHECK:             [[VAL_28:%.*]] = affine.apply #[[$MAP2]]([[VAL_16]]){{\[}}%[[C2]], %[[C0]]]
 // CHECK:             [[VAL_29:%.*]] = affine.apply #[[$MAP2]]([[VAL_17]]){{\[}}%[[C3]], %[[C0]]]
 // CHECK:             [[VAL_30:%.*]] = dim [[VAL_0]], %[[C0]] : memref<?x?xf32, #[[$MAP0]]>
 // CHECK:             [[VAL_31:%.*]] = affine.min #[[$MAP3]]([[VAL_28]]){{\[}}[[VAL_30]]]
 // CHECK:             [[VAL_31_SQUARED:%.*]] = muli [[VAL_31]], [[VAL_31]] : index
 // CHECK:             [[VAL_32:%.*]] = dim [[VAL_0]], %[[C1]] : memref<?x?xf32, #[[$MAP0]]>
 // CHECK:             [[VAL_33:%.*]] = affine.min #[[$MAP4]]([[VAL_29]]){{\[}}[[VAL_32]]]