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[mlir][llvm] Add icmp folder (#65343)
This revision adds a simple icmp folder that performs the following folds to the LLVM dialect icmp op: - cmpi(eq/ne, x, x) -> true/false - cmpi(eq/ne, alloca, null) -> false/true - cmpi(eq/ne, null, alloca) -> cmpi(eq/ne, alloca, null)
1 parent 71b5f57 commit 0c81e6d

3 files changed

Lines changed: 99 additions & 7 deletions

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‎mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td‎

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Original file line numberDiff line numberDiff line change
@@ -139,6 +139,7 @@ def LLVM_ICmpOp : LLVM_ArithmeticCmpOp<"icmp", [Pure]> {
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// Set the $predicate index to -1 to indicate there is no matching operand
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// and decrement the following indices.
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list<int> llvmArgIndices = [-1, 0, 1];
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let hasFolder = 1;
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}
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// Other floating-point operations.
@@ -1561,6 +1562,17 @@ def LLVM_ConstantOp
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}]>
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];
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let extraClassDeclaration = [{
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/// Whether the constant op can be constructed with a particular value and
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/// type.
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static bool isBuildableWith(Attribute value, Type type);
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/// Build the constant op with `value` and `type` if possible, otherwise
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/// returns null.
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static ConstantOp materialize(OpBuilder &builder, Attribute value,
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Type type, Location loc);
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}];
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let hasFolder = 1;
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let hasVerifier = 1;
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}

‎mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp‎

Lines changed: 58 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -98,7 +98,7 @@ static Type getI1SameShape(Type type) {
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}
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//===----------------------------------------------------------------------===//
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// Printing, parsing and builder for LLVM::CmpOp.
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// Printing, parsing, folding and builder for LLVM::CmpOp.
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//===----------------------------------------------------------------------===//
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void ICmpOp::print(OpAsmPrinter &p) {
@@ -175,6 +175,42 @@ ParseResult FCmpOp::parse(OpAsmParser &parser, OperationState &result) {
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return parseCmpOp<FCmpPredicate>(parser, result);
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}
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/// Returns a scalar or vector boolean attribute of the given type.
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static Attribute getBoolAttribute(Type type, MLIRContext *ctx, bool value) {
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auto boolAttr = BoolAttr::get(ctx, value);
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ShapedType shapedType = dyn_cast<ShapedType>(type);
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if (!shapedType)
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return boolAttr;
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return DenseElementsAttr::get(shapedType, boolAttr);
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}
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OpFoldResult ICmpOp::fold(FoldAdaptor adaptor) {
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if (getPredicate() != ICmpPredicate::eq &&
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getPredicate() != ICmpPredicate::ne)
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return {};
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// cmpi(eq/ne, x, x) -> true/false
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if (getLhs() == getRhs())
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return getBoolAttribute(getType(), getContext(),
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getPredicate() == ICmpPredicate::eq);
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// cmpi(eq/ne, alloca, null) -> false/true
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if (getLhs().getDefiningOp<AllocaOp>() && getRhs().getDefiningOp<NullOp>())
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return getBoolAttribute(getType(), getContext(),
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getPredicate() == ICmpPredicate::ne);
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// cmpi(eq/ne, null, alloca) -> cmpi(eq/ne, alloca, null)
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if (getLhs().getDefiningOp<NullOp>() && getRhs().getDefiningOp<AllocaOp>()) {
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Value lhs = getLhs();
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Value rhs = getRhs();
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getLhsMutable().assign(rhs);
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getRhsMutable().assign(lhs);
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return getResult();
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}
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return {};
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}
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//===----------------------------------------------------------------------===//
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// Printing, parsing and verification for LLVM::AllocaOp.
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//===----------------------------------------------------------------------===//
@@ -2443,7 +2479,7 @@ Region *LLVMFuncOp::getCallableRegion() {
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}
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//===----------------------------------------------------------------------===//
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// Verification for LLVM::ConstantOp.
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// ConstantOp.
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//===----------------------------------------------------------------------===//
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LogicalResult LLVM::ConstantOp::verify() {
@@ -2503,6 +2539,25 @@ LogicalResult LLVM::ConstantOp::verify() {
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return success();
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}
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bool LLVM::ConstantOp::isBuildableWith(Attribute value, Type type) {
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// The value's type must be the same as the provided type.
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auto typedAttr = dyn_cast<TypedAttr>(value);
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if (!typedAttr || typedAttr.getType() != type || !isCompatibleType(type))
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return false;
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// The value's type must be an LLVM compatible type.
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if (!isCompatibleType(type))
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return false;
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// TODO: Add support for additional attributes kinds once needed.
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return isa<IntegerAttr, FloatAttr, ElementsAttr>(value);
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}
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ConstantOp LLVM::ConstantOp::materialize(OpBuilder &builder, Attribute value,
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Type type, Location loc) {
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if (isBuildableWith(value, type))
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return builder.create<LLVM::ConstantOp>(loc, cast<TypedAttr>(value));
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return nullptr;
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}
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// Constant op constant-folds to its value.
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OpFoldResult LLVM::ConstantOp::fold(FoldAdaptor) { return getValue(); }
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@@ -3097,11 +3152,7 @@ LogicalResult LLVMDialect::verifyRegionResultAttribute(Operation *op,
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Operation *LLVMDialect::materializeConstant(OpBuilder &builder, Attribute value,
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Type type, Location loc) {
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// TODO: Accept more possible attributes. So far, only IntegerAttr may come
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// up.
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if (!isa<IntegerAttr>(value))
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return nullptr;
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return builder.create<LLVM::ConstantOp>(loc, type, value);
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return LLVM::ConstantOp::materialize(builder, value, type, loc);
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}
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//===----------------------------------------------------------------------===//

‎mlir/test/Dialect/LLVMIR/canonicalize.mlir‎

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,34 @@
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// RUN: mlir-opt --pass-pipeline='builtin.module(llvm.func(canonicalize{test-convergence}))' %s -split-input-file | FileCheck %s
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// CHECK-LABEL: @fold_icmp_eq
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llvm.func @fold_icmp_eq(%arg0 : i32) -> i1 {
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// CHECK: %[[C0:.*]] = llvm.mlir.constant(true) : i1
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%0 = llvm.icmp "eq" %arg0, %arg0 : i32
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// CHECK: llvm.return %[[C0]]
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llvm.return %0 : i1
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}
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// CHECK-LABEL: @fold_icmp_ne
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llvm.func @fold_icmp_ne(%arg0 : vector<2xi32>) -> vector<2xi1> {
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// CHECK: %[[C0:.*]] = llvm.mlir.constant(dense<false> : vector<2xi1>) : vector<2xi1>
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%0 = llvm.icmp "ne" %arg0, %arg0 : vector<2xi32>
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// CHECK: llvm.return %[[C0]]
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llvm.return %0 : vector<2xi1>
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}
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// CHECK-LABEL: @fold_icmp_alloca
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llvm.func @fold_icmp_alloca() -> i1 {
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// CHECK: %[[C0:.*]] = llvm.mlir.constant(true) : i1
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%c0 = llvm.mlir.null : !llvm.ptr
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%c1 = arith.constant 1 : i64
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%0 = llvm.alloca %c1 x i32 : (i64) -> !llvm.ptr
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%1 = llvm.icmp "ne" %c0, %0 : !llvm.ptr
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// CHECK: llvm.return %[[C0]]
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llvm.return %1 : i1
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}
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// -----
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// CHECK-LABEL: fold_extractvalue
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llvm.func @fold_extractvalue() -> i32 {
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// CHECK-DAG: %[[C0:.*]] = arith.constant 0 : i32

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