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[mlir][arith] Canonicalization patterns for arith.select #67809

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Oct 9, 2023
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[mlir][arith] Canonicalization patterns for arith.select #67809

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44 changes: 44 additions & 0 deletions mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
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Original file line number Diff line number Diff line change
Expand Up @@ -233,6 +233,50 @@ def CmpIExtUI :
CPred<"$0.getValue() == arith::CmpIPredicate::eq || "
"$0.getValue() == arith::CmpIPredicate::ne">> $pred)]>;

//===----------------------------------------------------------------------===//
// SelectOp
//===----------------------------------------------------------------------===//

// select(not(pred), a, b) => select(pred, b, a)
def SelectNotCond :
Pat<(SelectOp (Arith_XOrIOp $pred, (ConstantLikeMatcher APIntAttr:$ones)), $a, $b),
(SelectOp $pred, $b, $a),
[(IsScalarOrSplatNegativeOne $ones)]>;

// select(pred, select(pred, a, b), c) => select(pred, a, c)
def RedundantSelectTrue :
Pat<(SelectOp $pred, (SelectOp $pred, $a, $b), $c),
(SelectOp $pred, $a, $c)>;

// select(pred, a, select(pred, b, c)) => select(pred, a, c)
def RedundantSelectFalse :
Pat<(SelectOp $pred, $a, (SelectOp $pred, $b, $c)),
(SelectOp $pred, $a, $c)>;

// select(predA, select(predB, x, y), y) => select(and(predA, predB), x, y)
def SelectAndCond :
Pat<(SelectOp $predA, (SelectOp $predB, $x, $y), $y),
(SelectOp (Arith_AndIOp $predA, $predB), $x, $y)>;

// select(predA, select(predB, y, x), y) => select(and(predA, not(predB)), x, y)
def SelectAndNotCond :
Pat<(SelectOp $predA, (SelectOp $predB, $y, $x), $y),
(SelectOp (Arith_AndIOp $predA,
(Arith_XOrIOp $predB, (Arith_ConstantOp ConstantAttr<I1Attr, "1">))),
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FYI, this is wrong because it could be vector of i1 types, e.g., vector<4xi1>.

This patch introduces failure in downstream project (e.g., IREE). I'm working on a fix now.

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Here is a failure example:

  func.func @foo(%arg0: vector<4xf32>, %arg1: vector<4xf32>) -> vector<4xf32> {
    %0 = arith.cmpf ult, %arg0, %arg1 : vector<4xf32>
    %1 = arith.select %0, %arg0, %arg1 : vector<4xi1>, vector<4xf32>
    %2 = arith.cmpf uno, %arg1, %arg1 : vector<4xf32>
    %3 = arith.select %2, %arg1, %1 : vector<4xi1>, vector<4xf32>
    return %3 : vector<4xf32>
  }

$x, $y)>;

// select(predA, x, select(predB, x, y)) => select(or(predA, predB), x, y)
def SelectOrCond :
Pat<(SelectOp $predA, $x, (SelectOp $predB, $x, $y)),
(SelectOp (Arith_OrIOp $predA, $predB), $x, $y)>;

// select(predA, x, select(predB, y, x)) => select(or(predA, not(predB)), x, y)
def SelectOrNotCond :
Pat<(SelectOp $predA, $x, (SelectOp $predB, $y, $x)),
(SelectOp (Arith_OrIOp $predA,
(Arith_XOrIOp $predB, (Arith_ConstantOp ConstantAttr<I1Attr, "1">))),
$x, $y)>;

//===----------------------------------------------------------------------===//
// IndexCastOp
//===----------------------------------------------------------------------===//
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4 changes: 3 additions & 1 deletion mlir/lib/Dialect/Arith/IR/ArithOps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2212,7 +2212,9 @@ struct SelectToExtUI : public OpRewritePattern<arith::SelectOp> {

void arith::SelectOp::getCanonicalizationPatterns(RewritePatternSet &results,
MLIRContext *context) {
results.add<SelectI1Simplify, SelectToExtUI>(context);
results.add<RedundantSelectFalse, RedundantSelectTrue, SelectI1Simplify,
SelectAndCond, SelectAndNotCond, SelectOrCond, SelectOrNotCond,
SelectNotCond, SelectToExtUI>(context);
}

OpFoldResult arith::SelectOp::fold(FoldAdaptor adaptor) {
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76 changes: 76 additions & 0 deletions mlir/test/Dialect/Arith/canonicalize.mlir
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Expand Up @@ -128,6 +128,82 @@ func.func @selToArith(%arg0: i1, %arg1 : i1, %arg2 : i1) -> i1 {
return %res : i1
}

// CHECK-LABEL: @redundantSelectTrue
// CHECK-NEXT: %[[res:.+]] = arith.select %arg0, %arg1, %arg3
// CHECK-NEXT: return %[[res]]
func.func @redundantSelectTrue(%arg0: i1, %arg1 : i32, %arg2 : i32, %arg3 : i32) -> i32 {
%0 = arith.select %arg0, %arg1, %arg2 : i32
%res = arith.select %arg0, %0, %arg3 : i32
return %res : i32
}

// CHECK-LABEL: @redundantSelectFalse
// CHECK-NEXT: %[[res:.+]] = arith.select %arg0, %arg3, %arg2
// CHECK-NEXT: return %[[res]]
func.func @redundantSelectFalse(%arg0: i1, %arg1 : i32, %arg2 : i32, %arg3 : i32) -> i32 {
%0 = arith.select %arg0, %arg1, %arg2 : i32
%res = arith.select %arg0, %arg3, %0 : i32
return %res : i32
}

// CHECK-LABEL: @selNotCond
// CHECK-NEXT: %[[res1:.+]] = arith.select %arg0, %arg2, %arg1
// CHECK-NEXT: %[[res2:.+]] = arith.select %arg0, %arg4, %arg3
// CHECK-NEXT: return %[[res1]], %[[res2]]
func.func @selNotCond(%arg0: i1, %arg1 : i32, %arg2 : i32, %arg3 : i32, %arg4 : i32) -> (i32, i32) {
%one = arith.constant 1 : i1
%cond1 = arith.xori %arg0, %one : i1
%cond2 = arith.xori %one, %arg0 : i1

%res1 = arith.select %cond1, %arg1, %arg2 : i32
%res2 = arith.select %cond2, %arg3, %arg4 : i32
return %res1, %res2 : i32, i32
}

// CHECK-LABEL: @selAndCond
// CHECK-NEXT: %[[and:.+]] = arith.andi %arg1, %arg0
// CHECK-NEXT: %[[res:.+]] = arith.select %[[and]], %arg2, %arg3
// CHECK-NEXT: return %[[res]]
func.func @selAndCond(%arg0: i1, %arg1: i1, %arg2 : i32, %arg3 : i32) -> i32 {
%sel = arith.select %arg0, %arg2, %arg3 : i32
%res = arith.select %arg1, %sel, %arg3 : i32
return %res : i32
}

// CHECK-LABEL: @selAndNotCond
// CHECK-NEXT: %[[one:.+]] = arith.constant true
// CHECK-NEXT: %[[not:.+]] = arith.xori %arg0, %[[one]]
// CHECK-NEXT: %[[and:.+]] = arith.andi %arg1, %[[not]]
// CHECK-NEXT: %[[res:.+]] = arith.select %[[and]], %arg3, %arg2
// CHECK-NEXT: return %[[res]]
func.func @selAndNotCond(%arg0: i1, %arg1: i1, %arg2 : i32, %arg3 : i32) -> i32 {
%sel = arith.select %arg0, %arg2, %arg3 : i32
%res = arith.select %arg1, %sel, %arg2 : i32
return %res : i32
}

// CHECK-LABEL: @selOrCond
// CHECK-NEXT: %[[or:.+]] = arith.ori %arg1, %arg0
// CHECK-NEXT: %[[res:.+]] = arith.select %[[or]], %arg2, %arg3
// CHECK-NEXT: return %[[res]]
func.func @selOrCond(%arg0: i1, %arg1: i1, %arg2 : i32, %arg3 : i32) -> i32 {
%sel = arith.select %arg0, %arg2, %arg3 : i32
%res = arith.select %arg1, %arg2, %sel : i32
return %res : i32
}

// CHECK-LABEL: @selOrNotCond
// CHECK-NEXT: %[[one:.+]] = arith.constant true
// CHECK-NEXT: %[[not:.+]] = arith.xori %arg0, %[[one]]
// CHECK-NEXT: %[[or:.+]] = arith.ori %arg1, %[[not]]
// CHECK-NEXT: %[[res:.+]] = arith.select %[[or]], %arg3, %arg2
// CHECK-NEXT: return %[[res]]
func.func @selOrNotCond(%arg0: i1, %arg1: i1, %arg2 : i32, %arg3 : i32) -> i32 {
%sel = arith.select %arg0, %arg2, %arg3 : i32
%res = arith.select %arg1, %arg3, %sel : i32
return %res : i32
}

// Test case: Folding of comparisons with equal operands.
// CHECK-LABEL: @cmpi_equal_operands
// CHECK-DAG: %[[T:.*]] = arith.constant true
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