[Support] Add isShiftedUIntN to MathExtras.h

[craigblackmore]

Summary

This is a non-templated version of isShiftedUInt which takes N and S as arguments.

[craig.topper]

Can you add tests to unittests/Support/MathExtrasTest.cpp ?

llvm/include/llvm/Support/MathExtras.h

467

Assert that S > 0 like the template version.

[craigblackmore]

Thanks for the review. I have added asserts and unit tests.

[luismarques]

LGTM.

llvm/unittests/Support/MathExtrasTest.cpp

501–504

Nit: not a blocker but adding some ' digit group separators would help with the readability of the large constant literals. Most of this file probably predates that C++ spec feature but we could add them as we go.

llvm/include/llvm/Support/MathExtras.h

inline bool isUIntN(unsigned N, uint64_t x) {
   return N >= 64 || x <= maxUIntN(N);
 }
 
 /// Checks if an signed integer fits into the given (dynamic) bit width.
 inline bool isIntN(unsigned N, int64_t x) {
   return N >= 64 || (minIntN(N) <= x && x <= maxIntN(N));
 }
 
+/// Checks if an unsigned integer is an N bit number shifted left by S.  Dynamic
+/// version of isShiftedUInt.
+inline bool isShiftedUIntN(unsigned N, unsigned S, uint64_t x) {
+  assert(
+      N > 0 &&
+      "isShiftedUIntN(0, S, x) doesn't make sense (refers to a 0-bit number)");
+  assert(N + S <= 64 && "isShiftedUInt(N, S, x) with N + S > 64 is too wide.");
+  return isUIntN(N + S, x) && (x % (UINT64_C(1) << S) == 0);
+}
+
 /// Return true if the argument is a non-empty sequence of ones starting at the
 /// least significant bit with the remainder zero (32 bit version).
 /// Ex. isMask_32(0x0000FFFFU) == true.
 constexpr inline bool isMask_32(uint32_t Value) {
   return Value && ((Value + 1) & Value) == 0;
 }
 
 /// Return true if the argument is a non-empty sequence of ones starting at the

llvm/unittests/Support/MathExtrasTest.cpp

TEST(MathExtras, IsShiftedUInt) {
   EXPECT_FALSE((isShiftedUInt<2, 62>(0xE000000000000000)));
 
   // 0x201 is ten bits long and has a 1 in the MSB and LSB.
   EXPECT_TRUE((isShiftedUInt<10, 5>(uint64_t(0x201) << 5)));
   EXPECT_FALSE((isShiftedUInt<10, 5>(uint64_t(0x201) << 4)));
   EXPECT_FALSE((isShiftedUInt<10, 5>(uint64_t(0x201) << 6)));
 }
 
+TEST(MathExtras, IsShiftedUIntN) {
+  EXPECT_TRUE((isShiftedUIntN(1, 0, 0)));
+  EXPECT_TRUE((isShiftedUIntN(1, 0, 1)));
+  EXPECT_FALSE((isShiftedUIntN(1, 0, 2)));
+  EXPECT_FALSE((isShiftedUIntN(1, 0, 3)));
+  EXPECT_FALSE((isShiftedUIntN(1, 0, 0x8000000000000000)));
+  EXPECT_TRUE((isShiftedUIntN(1, 63, 0x8000000000000000)));
+  EXPECT_TRUE((isShiftedUIntN(2, 62, 0xC000000000000000)));
+  EXPECT_FALSE((isShiftedUIntN(2, 62, 0xE000000000000000)));
+
+  // 0x201 is ten bits long and has a 1 in the MSB and LSB.
+  EXPECT_TRUE((isShiftedUIntN(10, 5, (uint64_t(0x201) << 5))));
+  EXPECT_FALSE((isShiftedUIntN(10, 5, (uint64_t(0x201) << 4))));
+  EXPECT_FALSE((isShiftedUIntN(10, 5, (uint64_t(0x201) << 6))));
+}
+
 TEST(MathExtras, IsShiftedInt) {
   EXPECT_TRUE((isShiftedInt<1, 0>(0)));
   EXPECT_TRUE((isShiftedInt<1, 0>(-1)));
   EXPECT_FALSE((isShiftedInt<1, 0>(2)));
   EXPECT_FALSE((isShiftedInt<1, 0>(3)));
   EXPECT_FALSE((isShiftedInt<1, 0>(0x8000000000000000)));
   EXPECT_TRUE((isShiftedInt<1, 63>(0x8000000000000000)));
   EXPECT_TRUE((isShiftedInt<2, 62>(0xC000000000000000)));