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[mlir][licm] Make scf.if recursively speculatable #122031

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Jan 8, 2025
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[mlir][licm] Make scf.if recursively speculatable #122031

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4 changes: 2 additions & 2 deletions mlir/include/mlir/Dialect/SCF/IR/SCFOps.td
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Original file line number Diff line number Diff line change
Expand Up @@ -302,7 +302,7 @@ def ForallOp : SCF_Op<"forall", [
AttrSizedOperandSegments,
AutomaticAllocationScope,
DeclareOpInterfaceMethods<LoopLikeOpInterface,
["getInitsMutable", "getRegionIterArgs", "getLoopInductionVars",
["getInitsMutable", "getRegionIterArgs", "getLoopInductionVars",
"getLoopLowerBounds", "getLoopUpperBounds", "getLoopSteps",
"promoteIfSingleIteration", "yieldTiledValuesAndReplace"]>,
RecursiveMemoryEffects,
Expand Down Expand Up @@ -671,7 +671,7 @@ def IfOp : SCF_Op<"if", [DeclareOpInterfaceMethods<RegionBranchOpInterface, [
"getNumRegionInvocations", "getRegionInvocationBounds",
"getEntrySuccessorRegions"]>,
InferTypeOpAdaptor, SingleBlockImplicitTerminator<"scf::YieldOp">,
RecursiveMemoryEffects, NoRegionArguments]> {
RecursiveMemoryEffects, RecursivelySpeculatable, NoRegionArguments]> {
let summary = "if-then-else operation";
let description = [{
The `scf.if` operation represents an if-then-else construct for
Expand Down
121 changes: 121 additions & 0 deletions mlir/test/Transforms/loop-invariant-code-motion.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -124,6 +124,64 @@ func.func @invariant_affine_if() {

// -----

func.func @hoist_invariant_affine_if_success(%lb: index, %ub: index, %step: index) -> i32 {
%cst_0 = arith.constant 0 : i32
%cst_42 = arith.constant 42 : i32
%sum_result = affine.for %i = %lb to %ub iter_args(%acc = %cst_0) -> i32 {
%conditional_add = affine.if affine_set<() : ()> () -> (i32) {
%add = arith.addi %cst_42, %cst_42 : i32
affine.yield %add : i32
} else {
%poison = ub.poison : i32
affine.yield %poison : i32
}
%sum = arith.addi %acc, %conditional_add : i32
affine.yield %sum : i32
}

// CHECK-LABEL: hoist_invariant_affine_if_success
// CHECK-NEXT: arith.constant 0 : i32
// CHECK-NEXT: %[[CST:.*]] = arith.constant 42 : i32
// CHECK-NEXT: %[[IF:.*]] = affine.if
// CHECK-NEXT: arith.addi %[[CST]], %[[CST]] : i32
// CHECK: affine.for
// CHECK-NOT: affine.if
// CHECK-NEXT: arith.addi %{{.*}}, %[[IF]]

return %sum_result : i32
}

// -----

func.func @hoist_variant_affine_if_failure(%lb: index, %ub: index, %step: index) -> i32 {
%cst_0 = arith.constant 0 : i32
%cst_42 = arith.constant 42 : i32
%ind_7 = arith.constant 7 : index
%sum_result = affine.for %i = %lb to %ub iter_args(%acc = %cst_0) -> i32 {
%conditional_add = affine.if affine_set<(d0, d1) : (d1 - d0 >= 0)> (%i, %ind_7) -> (i32) {
%add = arith.addi %cst_42, %cst_42 : i32
affine.yield %add : i32
} else {
%poison = ub.poison : i32
affine.yield %poison : i32
}
%sum = arith.addi %acc, %conditional_add : i32
affine.yield %sum : i32
}

// CHECK-LABEL: hoist_variant_affine_if_failure
// CHECK-NEXT: arith.constant 0 : i32
// CHECK-NEXT: %[[CST:.*]] = arith.constant 42 : i32
// CHECK-NEXT: arith.constant 7 : index
// CHECK-NEXT: affine.for
// CHECK-NEXT: %[[IF:.*]] = affine.if
// CHECK: arith.addi %{{.*}}, %[[IF]]

return %sum_result : i32
}

// -----

func.func @hoist_affine_for_with_unknown_trip_count(%lb: index, %ub: index) {
affine.for %arg0 = 0 to 10 {
affine.for %arg1 = %lb to %ub {
Expand Down Expand Up @@ -383,6 +441,69 @@ func.func @parallel_loop_with_invariant() {

// -----

func.func @hoist_invariant_scf_if_success(%lb: index, %ub: index, %step: index) -> i32 {
%cst_0 = arith.constant 0 : i32
%cst_42 = arith.constant 42 : i32
%true = arith.constant true
%sum_result = scf.for %i = %lb to %ub step %step iter_args(%acc = %cst_0) -> i32 {
%conditional_add = scf.if %true -> (i32) {
%add = arith.addi %cst_42, %cst_42 : i32
scf.yield %add : i32
} else {
%poison = ub.poison : i32
scf.yield %poison : i32
}
%sum = arith.addi %acc, %conditional_add : i32
scf.yield %sum : i32
}

// CHECK-LABEL: hoist_invariant_scf_if_success
// CHECK-NEXT: arith.constant 0 : i32
// CHECK-NEXT: %[[CST:.*]] = arith.constant 42 : i32
// CHECK-NEXT: %[[TRUE:.*]] = arith.constant true
// CHECK-NEXT: %[[IF:.*]] = scf.if %[[TRUE]]
// CHECK-NEXT: arith.addi %[[CST]], %[[CST]] : i32
// CHECK: scf.for
// CHECK-NOT: scf.if
// CHECK-NEXT: arith.addi %{{.*}}, %[[IF]]

return %sum_result : i32
}

// -----

func.func @hoist_variant_scf_if_failure(%lb: index, %ub: index, %step: index) -> i32 {
%cst_0 = arith.constant 0 : i32
%cst_42 = arith.constant 42 : i32
%ind_7 = arith.constant 7 : index
%sum_result = scf.for %i = %lb to %ub step %step iter_args(%acc = %cst_0) -> i32 {
%cond = arith.cmpi ult, %i, %ind_7 : index
%conditional_add = scf.if %cond -> (i32) {
%add = arith.addi %cst_42, %cst_42 : i32
scf.yield %add : i32
} else {
%poison = ub.poison : i32
scf.yield %poison : i32
}
%sum = arith.addi %acc, %conditional_add : i32
scf.yield %sum : i32
}

// CHECK-LABEL: hoist_variant_scf_if_failure
// CHECK-NEXT: arith.constant 0 : i32
// CHECK-NEXT: %[[CST_42:.*]] = arith.constant 42 : i32
// CHECK-NEXT: %[[CST_7:.*]] = arith.constant 7 : index
// CHECK-NEXT: scf.for %[[IV:.*]] = %{{.*}} to %{{.*}}
// CHECK-NEXT: %[[CMP:.*]] = arith.cmpi ult, %[[IV]], %[[CST_7]]
// CHECK-NEXT: %[[IF:.*]] = scf.if %[[CMP]]
// CHECK-NEXT: arith.addi %[[CST_42]], %[[CST_42]] : i32
// CHECK: arith.addi %{{.*}}, %[[IF]]

return %sum_result : i32
}

// -----

func.func private @make_val() -> (index)

// CHECK-LABEL: func @nested_uses_inside
Expand Down
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