Restrict to default rounding mode.

Author: chsigg

mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td

@@ -423,15 +423,17 @@ def TruncIShrUIMulIToMulUIExtended :
 // TruncIOp
 //===----------------------------------------------------------------------===//
 
-// truncf(sitofp(x)) -> sitofp(x).
+// truncf(sitofp(x)) -> sitofp(x) if default rounding mode.
 def TruncFSIToFPToSIToFP :
     Pat<(Arith_TruncFOp:$tr (Arith_SIToFPOp:$fp $x), $rmf, $fmf),
-        (Arith_SIToFPOp $x)>;
+        (Arith_SIToFPOp $x),
+        [(Constraint<CPred<"$0 == nullptr">, "default rounding mode"> $rmf)]>;
 
-// truncf(sitofp(x)) -> sitofp(x).
+// truncf(uitofp(x)) -> uitofp(x) if default rounding mode.
 def TruncFUIToFPToUIToFP :
     Pat<(Arith_TruncFOp:$tr (Arith_UIToFPOp:$fp $x), $rmf, $fmf),
-        (Arith_UIToFPOp $x)>;
+        (Arith_UIToFPOp $x),
+        [(Constraint<CPred<"$0 == nullptr">, "default rounding mode"> $rmf)]>;
 
 //===----------------------------------------------------------------------===//
 // MulFOp