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[CIR][Transform] Add simplify transformation for select op #816

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Merged
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Sep 9, 2024
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[CIR][Transform] Add simplify transformation for select op #816

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17 changes: 13 additions & 4 deletions clang/lib/CIR/Dialect/IR/CIRDialect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1395,11 +1395,20 @@ void TernaryOp::build(OpBuilder &builder, OperationState &result, Value cond,

OpFoldResult SelectOp::fold(FoldAdaptor adaptor) {
auto condition = adaptor.getCondition();
if (!condition)
return nullptr;
if (condition) {
auto conditionValue = mlir::cast<mlir::cir::BoolAttr>(condition).getValue();
return conditionValue ? getTrueValue() : getFalseValue();
}

auto conditionValue = mlir::cast<mlir::cir::BoolAttr>(condition).getValue();
return conditionValue ? getTrueValue() : getFalseValue();
// cir.select if %0 then x else x -> x
auto trueValue = adaptor.getTrueValue();
auto falseValue = adaptor.getFalseValue();
if (trueValue && trueValue == falseValue)
return trueValue;
if (getTrueValue() == getFalseValue())
return getTrueValue();

return nullptr;
}

//===----------------------------------------------------------------------===//
Expand Down
42 changes: 41 additions & 1 deletion clang/lib/CIR/Dialect/Transforms/CIRSimplify.cpp
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Expand Up @@ -107,6 +107,45 @@ struct RemoveTrivialTry : public OpRewritePattern<TryOp> {
}
};

struct SimplifySelect : public OpRewritePattern<SelectOp> {
using OpRewritePattern<SelectOp>::OpRewritePattern;

LogicalResult matchAndRewrite(SelectOp op,
PatternRewriter &rewriter) const final {
mlir::Operation *trueValueOp = op.getTrueValue().getDefiningOp();
mlir::Operation *falseValueOp = op.getFalseValue().getDefiningOp();
auto trueValueConstOp =
mlir::dyn_cast_if_present<mlir::cir::ConstantOp>(trueValueOp);
auto falseValueConstOp =
mlir::dyn_cast_if_present<mlir::cir::ConstantOp>(falseValueOp);
if (!trueValueConstOp || !falseValueConstOp)
return mlir::failure();

auto trueValue =
mlir::dyn_cast<mlir::cir::BoolAttr>(trueValueConstOp.getValue());
auto falseValue =
mlir::dyn_cast<mlir::cir::BoolAttr>(falseValueConstOp.getValue());
if (!trueValue || !falseValue)
return mlir::failure();

// cir.select if %0 then #true else #false -> %0
if (trueValue.getValue() && !falseValue.getValue()) {
rewriter.replaceAllUsesWith(op, op.getCondition());
rewriter.eraseOp(op);
return mlir::success();
}

// cir.seleft if %0 then #false else #true -> cir.unary not %0
if (!trueValue.getValue() && falseValue.getValue()) {
rewriter.replaceOpWithNewOp<mlir::cir::UnaryOp>(
op, mlir::cir::UnaryOpKind::Not, op.getCondition());
return mlir::success();
}

return mlir::failure();
}
};

//===----------------------------------------------------------------------===//
// CIRSimplifyPass
//===----------------------------------------------------------------------===//
Expand All @@ -131,7 +170,8 @@ void populateMergeCleanupPatterns(RewritePatternSet &patterns) {
RemoveRedundantBranches,
RemoveEmptyScope,
RemoveEmptySwitch,
RemoveTrivialTry
RemoveTrivialTry,
SimplifySelect
>(patterns.getContext());
// clang-format on
}
Expand Down
36 changes: 35 additions & 1 deletion clang/test/CIR/Transforms/select.cir
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@@ -1,4 +1,4 @@
// RUN: cir-opt --canonicalize -o %t.cir %s
// RUN: cir-opt -cir-simplify -o %t.cir %s
// RUN: FileCheck --input-file=%t.cir %s

!s32i = !cir.int<s, 32>
Expand All @@ -23,4 +23,38 @@ module {
// CHECK: cir.func @fold_false(%[[ARG0:.+]]: !s32i, %[[ARG1:.+]]: !s32i) -> !s32i {
// CHECK-NEXT: cir.return %[[ARG1]] : !s32i
// CHECK-NEXT: }

cir.func @fold_to_const(%arg0 : !cir.bool) -> !s32i {
%0 = cir.const #cir.int<42> : !s32i
%1 = cir.select if %arg0 then %0 else %0 : (!cir.bool, !s32i, !s32i) -> !s32i
cir.return %1 : !s32i
}

// CHECK: cir.func @fold_to_const(%{{.+}}: !cir.bool) -> !s32i {
// CHECK-NEXT: %[[#A:]] = cir.const #cir.int<42> : !s32i
// CHECK-NEXT: cir.return %[[#A]] : !s32i
// CHECK-NEXT: }

cir.func @simplify_1(%arg0 : !cir.bool) -> !cir.bool {
%0 = cir.const #cir.bool<true> : !cir.bool
%1 = cir.const #cir.bool<false> : !cir.bool
%2 = cir.select if %arg0 then %0 else %1 : (!cir.bool, !cir.bool, !cir.bool) -> !cir.bool
cir.return %2 : !cir.bool
}

// CHECK: cir.func @simplify_1(%[[ARG0:.+]]: !cir.bool) -> !cir.bool {
// CHECK-NEXT: cir.return %[[ARG0]] : !cir.bool
// CHECK-NEXT: }

cir.func @simplify_2(%arg0 : !cir.bool) -> !cir.bool {
%0 = cir.const #cir.bool<false> : !cir.bool
%1 = cir.const #cir.bool<true> : !cir.bool
%2 = cir.select if %arg0 then %0 else %1 : (!cir.bool, !cir.bool, !cir.bool) -> !cir.bool
cir.return %2 : !cir.bool
}

// CHECK: cir.func @simplify_2(%[[ARG0:.+]]: !cir.bool) -> !cir.bool {
// CHECK-NEXT: %[[#A:]] = cir.unary(not, %[[ARG0]]) : !cir.bool, !cir.bool
// CHECK-NEXT: cir.return %[[#A]] : !cir.bool
// CHECK-NEXT: }
}