[Mlir-commits] [mlir] [mlir][arith] Canonicalize sitofp(truncf) -> sitofp, and uitofp. (PR #139925)

[llvmlistbot at llvm.org]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mlir-arith

Author: Christian Sigg (chsigg)

<details>
<summary>Changes</summary>

Add a canonicalization patterns that simplifies `truncf(sitofp(x))` to `sitofp(x)` and `truncf(uitofp(x))` to `uitofp(x)`.

This assumes that the destination type of truncf is representable by the intermediate type.

Note that the truncf semantics requires that the destination type is narrower than the source type, so this is true for all types I can possibly think of, but one could probably construct an artificial counter example.

Somewhat related: https://github.com/llvm/llvm-project/pull/128096

---
Full diff: https://github.com/llvm/llvm-project/pull/139925.diff


4 Files Affected:

- (modified) mlir/include/mlir/Dialect/Arith/IR/ArithOps.td (+1) 
- (modified) mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td (+14) 
- (modified) mlir/lib/Dialect/Arith/IR/ArithOps.cpp (+5) 
- (modified) mlir/test/Dialect/Arith/canonicalize.mlir (+10) 


``````````diff
diff --git a/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td b/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td
index d50b6aeca15c9..599b3b982ec7f 100644
--- a/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td
+++ b/mlir/include/mlir/Dialect/Arith/IR/ArithOps.td
@@ -1273,6 +1273,7 @@ def Arith_TruncFOp :
   ];
 
   let hasFolder = 1;
+  let hasCanonicalizer = 1;
   let hasVerifier = 1;
   let assemblyFormat = [{ $in ($roundingmode^)?
                           (`fastmath` `` $fastmath^)?
diff --git a/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td b/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
index 7e212df9029d1..7be73c4343639 100644
--- a/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
+++ b/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
@@ -419,6 +419,20 @@ def TruncIShrUIMulIToMulUIExtended :
        (ValueWiderThan $mul, $x),
        (TruncationMatchesShiftAmount $mul, $x, $c0)]>;
 
+//===----------------------------------------------------------------------===//
+// TruncIOp
+//===----------------------------------------------------------------------===//
+
+// truncf(sitofp(x)) -> sitofp(x).
+def TruncFSIToFPToSIToFP :
+    Pat<(Arith_TruncFOp:$tr (Arith_SIToFPOp:$fp $x), $rmf, $fmf),
+        (Arith_SIToFPOp $x)>;
+
+// truncf(sitofp(x)) -> sitofp(x).
+def TruncFUIToFPToUIToFP :
+    Pat<(Arith_TruncFOp:$tr (Arith_UIToFPOp:$fp $x), $rmf, $fmf),
+        (Arith_UIToFPOp $x)>;
+
 //===----------------------------------------------------------------------===//
 // MulFOp
 //===----------------------------------------------------------------------===//
diff --git a/mlir/lib/Dialect/Arith/IR/ArithOps.cpp b/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
index 3b308716c84dc..41f2d0f3425e2 100644
--- a/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
+++ b/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
@@ -1552,6 +1552,11 @@ OpFoldResult arith::TruncFOp::fold(FoldAdaptor adaptor) {
       });
 }
 
+void arith::TruncFOp::getCanonicalizationPatterns(RewritePatternSet &patterns,
+                                                  MLIRContext *context) {
+  patterns.add<TruncFSIToFPToSIToFP, TruncFUIToFPToUIToFP>(context);
+}
+
 bool arith::TruncFOp::areCastCompatible(TypeRange inputs, TypeRange outputs) {
   return checkWidthChangeCast<std::less, FloatType>(inputs, outputs);
 }
diff --git a/mlir/test/Dialect/Arith/canonicalize.mlir b/mlir/test/Dialect/Arith/canonicalize.mlir
index d62c5b18fd041..a5dab73a62fac 100644
--- a/mlir/test/Dialect/Arith/canonicalize.mlir
+++ b/mlir/test/Dialect/Arith/canonicalize.mlir
@@ -753,6 +753,16 @@ func.func @truncExtf3(%arg0: f32) -> f16 {
   return %truncf : f16
 }
 
+// CHECK-LABEL: @truncSitofp
+//       CHECK-NOT: truncf
+//       CHECK:     %[[SITOFP:.*]] = arith.sitofp %[[ARG0:.*]] : i32 to f32
+//       CHECK:     return %[[SITOFP]]
+func.func @truncSitofp(%arg0: i32) -> f32 {
+  %sitofp = arith.sitofp %arg0 : i32 to f64
+  %trunc = arith.truncf %sitofp : f64 to f32
+  return %trunc : f32
+}
+
 // TODO: We should also add a test for not folding arith.extf on information loss.
 // This may happen when extending f8E5M2FNUZ to f16.
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/139925