[mlir][math] Use math.h for M_PI_4 on WIN32

[sunshaoce]

Summary

Trying to fix build errors on WIN32 caused by D153656

[sunshaoce]

update

[jpienaar]

https://github.com/llvm/llvm-project/commit/75bd41f61d3247d4394ad0c46d23cc7c62261d63 should resolve the breakage (I saw that previous uses of these constants were also changed to follow that approach).

[yronglin]

Can we add these constants into llvm/Support/MathExtras.h?

[sunshaoce]

In D153706#4446862, @jpienaar wrote:

https://github.com/llvm/llvm-project/commit/75bd41f61d3247d4394ad0c46d23cc7c62261d63 should resolve the breakage (I saw that previous uses of these constants were also changed to follow that approach).

Thanks!

mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp

 //===- PolynomialApproximation.cpp - Approximate math operations ----------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements expansion of math operations to fast approximations
 // that do not rely on any of the library functions.
 //
 //===----------------------------------------------------------------------===//
 
+#ifdef _WIN32
+#define _USE_MATH_DEFINES
+#endif
+
 #include <climits>
 #include <cmath>
 #include <cstddef>
 
 #include "mlir/Dialect/Arith/IR/Arith.h"
 #include "mlir/Dialect/Math/IR/Math.h"
 #include "mlir/Dialect/Math/Transforms/Approximation.h"
 #include "mlir/Dialect/Math/Transforms/Passes.h"