From ee40ef7aafe54dba4acabcd68c003aef10bdaa2c Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu@google.com>
Date: Sat, 3 Sep 2022 23:27:13 -0700
Subject: [PATCH] [Support] Simplify isInt and isUInt with constexpr if (NFC)

Differential Revision: https://reviews.llvm.org/D132813
---
 llvm/include/llvm/Support/MathExtras.h | 55 +++++++++++++---------------------
 1 file changed, 20 insertions(+), 35 deletions(-)

diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index 44dc22c..2b2c47e 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -356,17 +356,16 @@ constexpr inline uint64_t Make_64(uint32_t High, uint32_t Low) {
 
 /// Checks if an integer fits into the given bit width.
 template <unsigned N> constexpr inline bool isInt(int64_t x) {
-  return N >= 64 || (-(INT64_C(1)<<(N-1)) <= x && x < (INT64_C(1)<<(N-1)));
-}
-// Template specializations to get better code for common cases.
-template <> constexpr inline bool isInt<8>(int64_t x) {
-  return static_cast<int8_t>(x) == x;
-}
-template <> constexpr inline bool isInt<16>(int64_t x) {
-  return static_cast<int16_t>(x) == x;
-}
-template <> constexpr inline bool isInt<32>(int64_t x) {
-  return static_cast<int32_t>(x) == x;
+  if constexpr (N == 8)
+    return static_cast<int8_t>(x) == x;
+  if constexpr (N == 16)
+    return static_cast<int16_t>(x) == x;
+  if constexpr (N == 32)
+    return static_cast<int32_t>(x) == x;
+  if constexpr (N < 64)
+    return -(INT64_C(1) << (N - 1)) <= x && x < (INT64_C(1) << (N - 1));
+  (void)x; // MSVC v19.25 warns that x is unused.
+  return true;
 }
 
 /// Checks if a signed integer is an N bit number shifted left by S.
@@ -379,34 +378,20 @@ constexpr inline bool isShiftedInt(int64_t x) {
 }
 
 /// Checks if an unsigned integer fits into the given bit width.
-///
-/// This is written as two functions rather than as simply
-///
-///   return N >= 64 || X < (UINT64_C(1) << N);
-///
-/// to keep MSVC from (incorrectly) warning on isUInt<64> that we're shifting
-/// left too many places.
-template <unsigned N>
-constexpr inline std::enable_if_t<(N < 64), bool> isUInt(uint64_t X) {
+template <unsigned N> constexpr inline bool isUInt(uint64_t x) {
   static_assert(N > 0, "isUInt<0> doesn't make sense");
-  return X < (UINT64_C(1) << (N));
-}
-template <unsigned N>
-constexpr inline std::enable_if_t<N >= 64, bool> isUInt(uint64_t) {
+  if constexpr (N == 8)
+    return static_cast<uint8_t>(x) == x;
+  if constexpr (N == 16)
+    return static_cast<uint16_t>(x) == x;
+  if constexpr (N == 32)
+    return static_cast<uint32_t>(x) == x;
+  if constexpr (N < 64)
+    return x < (UINT64_C(1) << (N));
+  (void)x; // MSVC v19.25 warns that x is unused.
   return true;
 }
 
-// Template specializations to get better code for common cases.
-template <> constexpr inline bool isUInt<8>(uint64_t x) {
-  return static_cast<uint8_t>(x) == x;
-}
-template <> constexpr inline bool isUInt<16>(uint64_t x) {
-  return static_cast<uint16_t>(x) == x;
-}
-template <> constexpr inline bool isUInt<32>(uint64_t x) {
-  return static_cast<uint32_t>(x) == x;
-}
-
 /// Checks if a unsigned integer is an N bit number shifted left by S.
 template <unsigned N, unsigned S>
 constexpr inline bool isShiftedUInt(uint64_t x) {
-- 
2.7.4