[mlir][math] Canonicalization for math.floor op

[Lewuathe]

Summary

Support constant folding for math.floor op as well as math.ceil.

[Mogball]

mlir/test/Dialect/Math/canonicalize.mlir

374

This doesn't seem like a useful test

[Lewuathe]

mlir/test/Dialect/Math/canonicalize.mlir

374

I thought it might be useful to check not to round if unnecessary as well as @ceil_fold2 does. We don't need both?

[Mogball]

mlir/test/Dialect/Math/canonicalize.mlir

374

Fair enough

[Mogball]

nit: can you retitle the revision to "Add folder" instead of "canonicalizer"? This patch doesn't add a canonicalizer

[Lewuathe]

Rebased on the latest main HEAD.

mlir/include/mlir/Dialect/Math/IR/MathOps.td

let description = [{
 
     Example:
 
     ```mlir
     // Scalar floor value.
     %a = math.floor %b : f64
     ```
   }];
+
+  let hasFolder = 1;
 }
 
 //===----------------------------------------------------------------------===//
 // FmaOp
 //===----------------------------------------------------------------------===//
 
 def Math_FmaOp : Math_FloatTernaryOp<"fma"> {
   let summary = "floating point fused multipy-add operation";

mlir/lib/Dialect/Math/IR/MathOps.cpp

OpFoldResult math::RoundEvenOp::fold(ArrayRef<Attribute> operands) {
   return constFoldUnaryOp<FloatAttr>(operands, [](const APFloat &a) {
     APFloat result(a);
     result.roundToIntegral(llvm::RoundingMode::NearestTiesToEven);
     return result;
   });
 }
 
 //===----------------------------------------------------------------------===//
+// FloorOp folder
+//===----------------------------------------------------------------------===//
+
+OpFoldResult math::FloorOp::fold(ArrayRef<Attribute> operands) {
+  return constFoldUnaryOp<FloatAttr>(operands, [](const APFloat &a) {
+    APFloat result(a);
+    result.roundToIntegral(llvm::RoundingMode::TowardNegative);
+    return result;
+  });
+}
+
+//===----------------------------------------------------------------------===//
 // RoundOp folder
 //===----------------------------------------------------------------------===//
 
 OpFoldResult math::RoundOp::fold(ArrayRef<Attribute> operands) {
   return constFoldUnaryOpConditional<FloatAttr>(
       operands, [](const APFloat &a) -> Optional<APFloat> {
         switch (a.getSizeInBits(a.getSemantics())) {
         case 64:

mlir/test/Dialect/Math/canonicalize.mlir

func.func @cos_fold() -> f32 {
   %r = math.cos %c : f32
   return %r : f32
 }
 
 // CHECK-LABEL: @cos_fold_vec
 // CHECK-NEXT: %[[cst:.+]] = arith.constant dense<[1.000000e+00, 0.540302277, 1.000000e+00, 0.540302277]> : vector<4xf32>
 // CHECK-NEXT:   return %[[cst]]
 func.func @cos_fold_vec() -> (vector<4xf32>) {
   %v1 = arith.constant dense<[0.0, 1.0, 0.0, 1.0]> : vector<4xf32>
   %0 = math.cos %v1 : vector<4xf32>
   return %0 : vector<4xf32>
 }
 
 // CHECK-LABEL: @roundeven_fold
 // CHECK-NEXT: %[[cst:.+]] = arith.constant 2.000000e+00 : f32
 // CHECK-NEXT:   return %[[cst]]
 func.func @roundeven_fold() -> f32 {

 // CHECK-LABEL: @round_fold_vec
 // CHECK-NEXT: %[[cst:.+]] = arith.constant dense<[1.000000e+00, -1.000000e+00, 2.000000e+00, -2.000000e+00]> : vector<4xf32>
 // CHECK-NEXT:   return %[[cst]]
 func.func @round_fold_vec() -> (vector<4xf32>) {
   %v1 = arith.constant dense<[0.5, -0.5, 1.5, -1.5]> : vector<4xf32>
   %0 = math.round %v1 : vector<4xf32>
   return %0 : vector<4xf32>
 }
+
+// CHECK-LABEL: @floor_fold
+// CHECK: %[[cst:.+]] = arith.constant 0.000000e+00 : f32
+// CHECK: return %[[cst]]
+func.func @floor_fold() -> f32 {
+  %c = arith.constant 0.3 : f32
+  %r = math.floor %c : f32
+  return %r : f32
+}
+
+// CHECK-LABEL: @floor_fold2
+// CHECK: %[[cst:.+]] = arith.constant 2.000000e+00 : f32
+// CHECK: return %[[cst]]
+func.func @floor_fold2() -> f32 {
+  %c = arith.constant 2.0 : f32
+  %r = math.floor %c : f32
+  return %r : f32
+}