Add 'exact' flag to arith.shrui/shrsi/divsi/divui operations (#165923)

This MR adds support for the `exact` flag to the
`arith.shrui/shrsi/divsi/divui` operations. The semantics are identical
to those of the LLVM dialect and the LLVM language reference.

This MR also modifies the mechanism for converting `arith` dialect
**attributes** to corresponding **properties** in the `LLVM` dialect.
(As a specific example, the integer overflow flags `nsw/nuw` are
**properties** in the `LLVM` dialect, as opposed to attributes.)

Previously, attribute converter classes were required to have a specific
method to support integer overflow flags:
```C++
template <typename SourceOp, typename TargetOp>
class AttrConvertPassThrough {
public:
  ...
  LLVM::IntegerOverflowFlags getOverflowFlags() const {
    return LLVM::IntegerOverflowFlags::none;
  }
};
```
This method was required, even for `arith` source operations that did
not use integer overflow flags (e.g. `AttrConvertFastMathToLLVM`).

This MR modifies the interface required by `arith` dialect attribute
converters to instead provide a (possibly NULL) properties attribute:
```C++
template <typename SourceOp, typename TargetOp>
class AttrConvertPassThrough {
public:
  ...
  Attribute getPropAttr() const { return {}; }
};
```
For `arith` operations with attributes that map to `LLVM` dialect
**properties**, the attribute converter can create a `DictionaryAttr`
containing target properties and return that attribute from the
attribute converter's `getPropAttr()` method. The `arith` attribute
conversion framework will set the `propertiesAttr` of an
`OperationState`, and the target operation's `setPropertiesFromAttr()`
method will be invoked to set the properties when the target operation
is created. The `AttrConvertOverflowToLLVM` class in this MR uses the
new approach.

4 files changed, 92 insertions, 48 deletions

diff --git a/mlir/include/mlir/Conversion/ArithCommon/AttrToLLVMConverter.h b/mlir/include/mlir/Conversion/ArithCommon/AttrToLLVMConverter.h
index 7ffc86133176..7020e24517d0 100644
--- a/mlir/include/mlir/Conversion/ArithCommon/AttrToLLVMConverter.h
+++ b/mlir/include/mlir/Conversion/ArithCommon/AttrToLLVMConverter.h
@@ -65,11 +65,8 @@ public:
                         convertArithFastMathAttrToLLVM(arithFMFAttr));
     }
   }
-
   ArrayRef<NamedAttribute> getAttrs() const { return convertedAttr.getAttrs(); }
-  LLVM::IntegerOverflowFlags getOverflowFlags() const {
-    return LLVM::IntegerOverflowFlags::none;
-  }
+  Attribute getPropAttr() const { return {}; }
 
 private:
   NamedAttrList convertedAttr;
@@ -82,23 +79,36 @@ template <typename SourceOp, typename TargetOp>
 class AttrConvertOverflowToLLVM {
 public:
   AttrConvertOverflowToLLVM(SourceOp srcOp) {
+    using IntegerOverflowFlagsAttr = LLVM::IntegerOverflowFlagsAttr;
+
     // Copy the source attributes.
     convertedAttr = NamedAttrList{srcOp->getAttrs()};
     // Get the name of the arith overflow attribute.
     StringRef arithAttrName = SourceOp::getIntegerOverflowAttrName();
-    // Remove the source overflow attribute.
+    // Remove the source overflow attribute from the set that will be present
+    // in the target.
     if (auto arithAttr = dyn_cast_if_present<arith::IntegerOverflowFlagsAttr>(
             convertedAttr.erase(arithAttrName))) {
-      overflowFlags = convertArithOverflowFlagsToLLVM(arithAttr.getValue());
+      auto llvmFlag = convertArithOverflowFlagsToLLVM(arithAttr.getValue());
+      // Create a dictionary attribute holding the overflow flags property.
+      // (In the LLVM dialect, the overflow flags are a property, not an
+      // attribute.)
+      MLIRContext *ctx = srcOp.getOperation()->getContext();
+      Builder b(ctx);
+      auto llvmFlagAttr = IntegerOverflowFlagsAttr::get(ctx, llvmFlag);
+      StringRef llvmAttrName = TargetOp::getOverflowFlagsAttrName();
+      NamedAttribute attr{llvmAttrName, llvmFlagAttr};
+      // Set the properties attribute of the operation state so that the
+      // property can be updated when the operation is created.
+      propertiesAttr = b.getDictionaryAttr(ArrayRef(attr));
     }
   }
-
   ArrayRef<NamedAttribute> getAttrs() const { return convertedAttr.getAttrs(); }
-  LLVM::IntegerOverflowFlags getOverflowFlags() const { return overflowFlags; }
+  Attribute getPropAttr() const { return propertiesAttr; }
 
 private:
   NamedAttrList convertedAttr;
-  LLVM::IntegerOverflowFlags overflowFlags = LLVM::IntegerOverflowFlags::none;
+  DictionaryAttr propertiesAttr;
 };
 
 template <typename SourceOp, typename TargetOp>
@@ -129,9 +139,7 @@ public:
   }
 
   ArrayRef<NamedAttribute> getAttrs() const { return convertedAttr.getAttrs(); }
-  LLVM::IntegerOverflowFlags getOverflowFlags() const {
-    return LLVM::IntegerOverflowFlags::none;
-  }
+  Attribute getPropAttr() const { return {}; }
 
 private:
   NamedAttrList convertedAttr;
diff --git a/mlir/include/mlir/Conversion/LLVMCommon/Pattern.h b/mlir/include/mlir/Conversion/LLVMCommon/Pattern.h
index c292e3727f46..f8e0ccc093f8 100644
--- a/mlir/include/mlir/Conversion/LLVMCommon/Pattern.h
+++ b/mlir/include/mlir/Conversion/LLVMCommon/Pattern.h
@@ -19,16 +19,14 @@ class CallOpInterface;
 
 namespace LLVM {
 namespace detail {
-/// Handle generically setting flags as native properties on LLVM operations.
-void setNativeProperties(Operation *op, IntegerOverflowFlags overflowFlags);
-
 /// Replaces the given operation "op" with a new operation of type "targetOp"
 /// and given operands.
-LogicalResult oneToOneRewrite(
-    Operation *op, StringRef targetOp, ValueRange operands,
-    ArrayRef<NamedAttribute> targetAttrs,
-    const LLVMTypeConverter &typeConverter, ConversionPatternRewriter &rewriter,
-    IntegerOverflowFlags overflowFlags = IntegerOverflowFlags::none);
+LogicalResult oneToOneRewrite(Operation *op, StringRef targetOp,
+                              ValueRange operands,
+                              ArrayRef<NamedAttribute> targetAttrs,
+                              Attribute propertiesAttr,
+                              const LLVMTypeConverter &typeConverter,
+                              ConversionPatternRewriter &rewriter);
 
 /// Replaces the given operation "op" with a call to an LLVM intrinsic with the
 /// specified name "intrinsic" and operands.
@@ -307,9 +305,9 @@ public:
   LogicalResult
   matchAndRewrite(SourceOp op, typename SourceOp::Adaptor adaptor,
                   ConversionPatternRewriter &rewriter) const override {
-    return LLVM::detail::oneToOneRewrite(op, TargetOp::getOperationName(),
-                                         adaptor.getOperands(), op->getAttrs(),
-                                         *this->getTypeConverter(), rewriter);
+    return LLVM::detail::oneToOneRewrite(
+        op, TargetOp::getOperationName(), adaptor.getOperands(), op->getAttrs(),
+        /*propertiesAttr=*/Attribute{}, *this->getTypeConverter(), rewriter);
   }
 };
 
diff --git a/mlir/include/mlir/Conversion/LLVMCommon/VectorPattern.h b/mlir/include/mlir/Conversion/LLVMCommon/VectorPattern.h
index e7ab63abfeaa..47b8381eefda 100644
--- a/mlir/include/mlir/Conversion/LLVMCommon/VectorPattern.h
+++ b/mlir/include/mlir/Conversion/LLVMCommon/VectorPattern.h
@@ -54,25 +54,26 @@ LogicalResult handleMultidimensionalVectors(
     std::function<Value(Type, ValueRange)> createOperand,
     ConversionPatternRewriter &rewriter);
 
-LogicalResult vectorOneToOneRewrite(
-    Operation *op, StringRef targetOp, ValueRange operands,
-    ArrayRef<NamedAttribute> targetAttrs,
-    const LLVMTypeConverter &typeConverter, ConversionPatternRewriter &rewriter,
-    IntegerOverflowFlags overflowFlags = IntegerOverflowFlags::none);
+LogicalResult vectorOneToOneRewrite(Operation *op, StringRef targetOp,
+                                    ValueRange operands,
+                                    ArrayRef<NamedAttribute> targetAttrs,
+                                    Attribute propertiesAttr,
+                                    const LLVMTypeConverter &typeConverter,
+                                    ConversionPatternRewriter &rewriter);
 } // namespace detail
 } // namespace LLVM
 
 // Default attribute conversion class, which passes all source attributes
-// through to the target op, unmodified.
+// through to the target op, unmodified. The attribute to set properties of the
+// target operation will be nullptr (i.e. any properties that exist in will have
+// default values).
 template <typename SourceOp, typename TargetOp>
 class AttrConvertPassThrough {
 public:
   AttrConvertPassThrough(SourceOp srcOp) : srcAttrs(srcOp->getAttrs()) {}
 
   ArrayRef<NamedAttribute> getAttrs() const { return srcAttrs; }
-  LLVM::IntegerOverflowFlags getOverflowFlags() const {
-    return LLVM::IntegerOverflowFlags::none;
-  }
+  Attribute getPropAttr() const { return {}; }
 
 private:
   ArrayRef<NamedAttribute> srcAttrs;
@@ -80,10 +81,13 @@ private:
 
 /// Basic lowering implementation to rewrite Ops with just one result to the
 /// LLVM Dialect. This supports higher-dimensional vector types.
-/// The AttrConvert template template parameter should be a template class
-/// with SourceOp and TargetOp type parameters, a constructor that takes
-/// a SourceOp instance, and a getAttrs() method that returns
-/// ArrayRef<NamedAttribute>.
+/// The AttrConvert template template parameter should:
+//  - be a template class with SourceOp and TargetOp type parameters
+//  - have a constructor that takes a SourceOp instance
+//  - a getAttrs() method that returns ArrayRef<NamedAttribute> containing
+//    attributes that the target operation will have
+//  - a getPropAttr() method that returns either a NULL attribute or a
+//    DictionaryAttribute with properties that exist for the target operation
 template <typename SourceOp, typename TargetOp,
           template <typename, typename> typename AttrConvert =
               AttrConvertPassThrough,
@@ -137,8 +141,8 @@ public:
 
     return LLVM::detail::vectorOneToOneRewrite(
         op, TargetOp::getOperationName(), adaptor.getOperands(),
-        attrConvert.getAttrs(), *this->getTypeConverter(), rewriter,
-        attrConvert.getOverflowFlags());
+        attrConvert.getAttrs(), attrConvert.getPropAttr(),
+        *this->getTypeConverter(), rewriter);
   }
 };
 } // namespace mlir
diff --git a/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td b/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td
index a38cf41a3e09..77d780425c3c 100644
--- a/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td
+++ b/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td
@@ -158,6 +158,18 @@ class Arith_IntBinaryOpWithOverflowFlags<string mnemonic, list<Trait> traits = [
                           attr-dict `:` type($result) }];
 }
 
+class Arith_IntBinaryOpWithExactFlag<string mnemonic, list<Trait> traits = []> :
+    Arith_BinaryOp<mnemonic, traits #
+      [DeclareOpInterfaceMethods<InferIntRangeInterface, ["inferResultRanges"]>]>,
+    Arguments<(ins SignlessIntegerOrIndexLike:$lhs,
+               SignlessIntegerOrIndexLike:$rhs,
+               UnitAttr:$isExact)>,
+    Results<(outs SignlessIntegerOrIndexLike:$result)> {
+
+  let assemblyFormat = [{ $lhs `,` $rhs (`exact` $isExact^)?
+                          attr-dict `:` type($result) }];
+}
+
 //===----------------------------------------------------------------------===//
 // ConstantOp
 //===----------------------------------------------------------------------===//
@@ -482,7 +494,8 @@ def Arith_MulUIExtendedOp : Arith_Op<"mului_extended", [Pure, Commutative,
 // DivUIOp
 //===----------------------------------------------------------------------===//
 
-def Arith_DivUIOp : Arith_IntBinaryOp<"divui", [ConditionallySpeculatable]> {
+def Arith_DivUIOp : Arith_IntBinaryOpWithExactFlag<"divui",
+                                                   [ConditionallySpeculatable]> {
   let summary = "unsigned integer division operation";
   let description = [{
     Unsigned integer division. Rounds towards zero. Treats the leading bit as
@@ -493,12 +506,18 @@ def Arith_DivUIOp : Arith_IntBinaryOp<"divui", [ConditionallySpeculatable]> {
     `tensor` values, the behavior is undefined if _any_ elements are divided by
     zero.
 
+    If the `exact` attribute is present, the result value is poison if `lhs` is
+    not a multiple of `rhs`.
+
     Example:
 
     ```mlir
     // Scalar unsigned integer division.
     %a = arith.divui %b, %c : i64
 
+    // Scalar unsigned integer division where %b is known to be a multiple of %c.
+    %a = arith.divui %b, %c exact : i64
+
     // SIMD vector element-wise division.
     %f = arith.divui %g, %h : vector<4xi32>
 
@@ -519,7 +538,8 @@ def Arith_DivUIOp : Arith_IntBinaryOp<"divui", [ConditionallySpeculatable]> {
 // DivSIOp
 //===----------------------------------------------------------------------===//
 
-def Arith_DivSIOp : Arith_IntBinaryOp<"divsi", [ConditionallySpeculatable]> {
+def Arith_DivSIOp : Arith_IntBinaryOpWithExactFlag<"divsi",
+                                                   [ConditionallySpeculatable]> {
   let summary = "signed integer division operation";
   let description = [{
     Signed integer division. Rounds towards zero. Treats the leading bit as
@@ -530,12 +550,18 @@ def Arith_DivSIOp : Arith_IntBinaryOp<"divsi", [ConditionallySpeculatable]> {
     behavior is undefined if _any_ of its elements are divided by zero or has a
     signed division overflow.
 
+    If the `exact` attribute is present, the result value is poison if `lhs` is
+    not a multiple of `rhs`.
+
     Example:
 
     ```mlir
     // Scalar signed integer division.
     %a = arith.divsi %b, %c : i64
 
+    // Scalar signed integer division where %b is known to be a multiple of %c.
+    %a = arith.divsi %b, %c exact : i64
+
     // SIMD vector element-wise division.
     %f = arith.divsi %g, %h : vector<4xi32>
 
@@ -821,7 +847,7 @@ def Arith_ShLIOp : Arith_IntBinaryOpWithOverflowFlags<"shli"> {
 // ShRUIOp
 //===----------------------------------------------------------------------===//
 
-def Arith_ShRUIOp : Arith_TotalIntBinaryOp<"shrui"> {
+def Arith_ShRUIOp : Arith_IntBinaryOpWithExactFlag<"shrui", [Pure]> {
   let summary = "unsigned integer right-shift";
   let description = [{
     The `shrui` operation shifts an integer value of the first operand to the right
@@ -830,12 +856,17 @@ def Arith_ShRUIOp : Arith_TotalIntBinaryOp<"shrui"> {
     filled with zeros. If the value of the second operand is greater or equal than the
     bitwidth of the first operand, then the operation returns poison.
 
+    If the `exact` attribute is present, the result value of shrui is a poison
+    value if any of the bits shifted out are non-zero.
+
     Example:
 
     ```mlir
-    %1 = arith.constant 160 : i8               // %1 is 0b10100000
+    %1 = arith.constant 160 : i8        // %1 is 0b10100000
     %2 = arith.constant 3 : i8
-    %3 = arith.shrui %1, %2 : (i8, i8) -> i8   // %3 is 0b00010100
+    %3 = arith.constant 6 : i8
+    %4 = arith.shrui %1, %2 exact : i8  // %4 is 0b00010100
+    %5 = arith.shrui %1, %3 : i8        // %3 is 0b00000010
     ```
   }];
   let hasFolder = 1;
@@ -845,7 +876,7 @@ def Arith_ShRUIOp : Arith_TotalIntBinaryOp<"shrui"> {
 // ShRSIOp
 //===----------------------------------------------------------------------===//
 
-def Arith_ShRSIOp : Arith_TotalIntBinaryOp<"shrsi"> {
+def Arith_ShRSIOp : Arith_IntBinaryOpWithExactFlag<"shrsi", [Pure]> {
   let summary = "signed integer right-shift";
   let description = [{
     The `shrsi` operation shifts an integer value of the first operand to the right
@@ -856,14 +887,17 @@ def Arith_ShRSIOp : Arith_TotalIntBinaryOp<"shrsi"> {
     operand is greater or equal than bitwidth of the first operand, then the operation
     returns poison.
 
+    If the `exact` attribute is present, the result value of shrsi is a poison
+    value if any of the bits shifted out are non-zero.
+
     Example:
 
     ```mlir
-    %1 = arith.constant 160 : i8               // %1 is 0b10100000
+    %1 = arith.constant 160 : i8         // %1 is 0b10100000
     %2 = arith.constant 3 : i8
-    %3 = arith.shrsi %1, %2 : (i8, i8) -> i8   // %3 is 0b11110100
-    %4 = arith.constant 96 : i8                   // %4 is 0b01100000
-    %5 = arith.shrsi %4, %2 : (i8, i8) -> i8   // %5 is 0b00001100
+    %3 = arith.shrsi %1, %2 exact : i8   // %3 is 0b11110100
+    %4 = arith.constant 98 : i8          // %4 is 0b01100010
+    %5 = arith.shrsi %4, %2 : i8         // %5 is 0b00001100
     ```
   }];
   let hasFolder = 1;