[mlir][tosa] Fix windows build-bot error due to implicit i64 cast

[rsuderman]

Summary

There is an implicit i64 cast due to the << during MulOp's folder.

[stella.stamenova]

LGTM

[stella.stamenova]

It looks like this was not enough and you'll need an explicit cast. There's also a second one a few lines down: https://lab.llvm.org/buildbot/#/builders/13/builds/25203/steps/6/logs/stdio

[stella.stamenova]

The windows mlir bot is still broken, if we can't get a fix today, I'll go ahead and revert the changes:

https://lab.llvm.org/buildbot/#/builders/13/builds/25203/steps/6/logs/stdio

[rsuderman]

Generally we prefer to fix forward MSVC compiler errors as the LLVM CI runs a clang build, as many contributors do not have access to windows development machines.

mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp

if (rhsAttr && rhsAttr.isSplat() && resultETy.isa<FloatType>()) {
     if (val.isExactlyValue(1.0))
       return lhs;
   }
 
   if (lhsAttr && lhsAttr.isSplat() && resultETy.isa<IntegerType>()) {
     auto val = lhsAttr.getSplatValue<APInt>();
     if (val.isZero())
       return lhsAttr;
-    if (val.getSExtValue() == (1 << getShift()))
+    const int64_t shift = getShift();
+    const int64_t shifted = 1 << shift;
+    if (val.getSExtValue() == shifted)
       return rhs;
   }
 
   if (rhsAttr && rhsAttr.isSplat() && resultETy.isa<IntegerType>()) {
     auto val = rhsAttr.getSplatValue<APInt>();
     if (val.isZero())
       return rhsAttr;
     if (val.getSExtValue() == (1 << getShift()))