[mlir][Arith] Fix bug in zero-extension range inference

[krzysz00]

Summary

D135089 extracted the extui code into a helper, but used fromSigned
instead of fromUnsigned.

mlir/lib/Dialect/Arith/IR/InferIntRangeInterfaceImpls.cpp

 
 //===----------------------------------------------------------------------===//
 // ExtUIOp
 //===----------------------------------------------------------------------===//
 
 static ConstantIntRanges extUIRange(const ConstantIntRanges &range,
                                     Type destType) {
   unsigned destWidth = ConstantIntRanges::getStorageBitwidth(destType);
-  APInt smin = range.umin().zext(destWidth);
-  APInt smax = range.umax().zext(destWidth);
-  return ConstantIntRanges::fromSigned(smin, smax);
+  APInt umin = range.umin().zext(destWidth);
+  APInt umax = range.umax().zext(destWidth);
+  return ConstantIntRanges::fromUnsigned(umin, umax);
 }
 
 void arith::ExtUIOp::inferResultRanges(ArrayRef<ConstantIntRanges> argRanges,
                                        SetIntRangeFn setResultRange) {
   Type destType = getResult().getType();
   setResultRange(getResult(), extUIRange(argRanges[0], destType));
 }
 

mlir/test/Dialect/Arith/int-range-interface.mlir

func.func @trunc_handles_small_signed_ranges(%arg0 : i16) -> i1 {
     %0 = arith.maxsi %arg0, %c-2_i16 : i16
     %1 = arith.minsi %0, %c2_i16 : i16
     %2 = arith.trunci %1 : i16 to i8
     %3 = arith.cmpi sge, %2, %c-2_i8 : i8
     %4 = arith.cmpi sle, %2, %c2_i8 : i8
     %5 = arith.andi %3, %4 : i1
     func.return %5 : i1
 }
+
+/// Catch a bug that crept in during an earlier refactoring that made unsigned
+/// extension use the signed ranges
+
+// CHECK-LABEL: func.func @extui_uses_unsigned
+// CHECK: %[[true:.*]] = arith.constant true
+// CHECK: return %[[true]]
+func.func @extui_uses_unsigned(%arg0 : i32) -> i1 {
+    %ci32_smin = arith.constant 0x80000000 : i32
+    %ci32_smin_64 = arith.constant 0x80000000 : i64
+    %c0_i64 = arith.constant 0 : i64
+    %0 = arith.minui %arg0, %ci32_smin : i32
+    %1 = arith.extui %0 : i32 to i64
+    %2 = arith.cmpi sge, %1, %c0_i64 : i64
+    %3 = arith.cmpi ule, %1, %ci32_smin_64 : i64
+    %4 = arith.andi %2, %3 : i1
+    func.return %4 : i1
+}