Remove newly added asserts from pg_bitutils.h

These were valuable during development, but are unlikely to tell us
anything going forward. This reverts 204b0cbec and adjusts the content
of 677319746 to more closely match the more-readable original style.

Per review from Tom Lane

Discussion: https://www.postgresql.org/message-id/3567481.1676906261%40sss.pgh.pa.us

src/include/port/pg_bitutils.h

@@ -41,14 +41,17 @@ static inline int
 pg_leftmost_one_pos32(uint32 word)
 {
 #ifdef HAVE__BUILTIN_CLZ
-	int			bitscan_result;
+	Assert(word != 0);
+
+	return 31 - __builtin_clz(word);
 #elif defined(_MSC_VER)
-	unsigned long bitscan_result;
+	unsigned long result;
 	bool		non_zero;
-#endif
 
-#if !defined(HAVE_BITSCAN_REVERSE) || defined(USE_ASSERT_CHECKING)
-	int			result;
+	non_zero = _BitScanReverse(&result, word);
+	Assert(non_zero);
+	return (int) result;
+#else
 	int			shift = 32 - 8;
 
 	Assert(word != 0);
@@ -56,23 +59,8 @@ pg_leftmost_one_pos32(uint32 word)
 	while ((word >> shift) == 0)
 		shift -= 8;
 
-	result = shift + pg_leftmost_one_pos[(word >> shift) & 255];
-#endif
-
-#ifdef HAVE_BITSCAN_REVERSE
-
-#if defined(HAVE__BUILTIN_CLZ)
-	bitscan_result = 31 - __builtin_clz(word);
-#elif defined(_MSC_VER)
-	non_zero = _BitScanReverse(&bitscan_result, word);
-	Assert(non_zero);
-#endif
-	Assert(bitscan_result == result);
-	return bitscan_result;
-
-#else
-	return result;
-#endif							/* HAVE_BITSCAN_REVERSE */
+	return shift + pg_leftmost_one_pos[(word >> shift) & 255];
+#endif							/* HAVE__BUILTIN_CLZ */
 }
 
 /*
@@ -83,45 +71,33 @@ static inline int
 pg_leftmost_one_pos64(uint64 word)
 {
 #ifdef HAVE__BUILTIN_CLZ
-	int			bitscan_result;
-#elif defined(_MSC_VER)
-	unsigned long bitscan_result;
-	bool		non_zero;
-#endif
-
-#if !defined(HAVE_BITSCAN_REVERSE) || defined(USE_ASSERT_CHECKING)
-	int			result;
-	int			shift = 64 - 8;
-
 	Assert(word != 0);
 
-	while ((word >> shift) == 0)
-		shift -= 8;
-
-	result = shift + pg_leftmost_one_pos[(word >> shift) & 255];
-#endif
-
-#ifdef HAVE_BITSCAN_REVERSE
-
-#if defined(HAVE__BUILTIN_CLZ)
 #if defined(HAVE_LONG_INT_64)
-	bitscan_result = 63 - __builtin_clzl(word);
+	return 63 - __builtin_clzl(word);
 #elif defined(HAVE_LONG_LONG_INT_64)
-	bitscan_result = 63 - __builtin_clzll(word);
+	return 63 - __builtin_clzll(word);
 #else
 #error must have a working 64-bit integer datatype
 #endif							/* HAVE_LONG_INT_64 */
 
 #elif defined(_MSC_VER)
-	non_zero = _BitScanReverse64(&bitscan_result, word);
-	Assert(non_zero);
-#endif							/* HAVE__BUILTIN_CLZ */
-	Assert(bitscan_result == result);
-	return bitscan_result;
+	unsigned long result;
+	bool		non_zero;
 
+	non_zero = _BitScanReverse64(&result, word);
+	Assert(non_zero);
+	return (int) result;
 #else
-	return result;
-#endif							/* HAVE_BITSCAN_REVERSE */
+	int			shift = 64 - 8;
+
+	Assert(word != 0);
+
+	while ((word >> shift) == 0)
+		shift -= 8;
+
+	return shift + pg_leftmost_one_pos[(word >> shift) & 255];
+#endif							/* HAVE__BUILTIN_CLZ */
 }
 
 /*
@@ -133,15 +109,17 @@ static inline int
 pg_rightmost_one_pos32(uint32 word)
 {
 #ifdef HAVE__BUILTIN_CTZ
-	const uint32 orig_word = word;
-	int			bitscan_result;
+	Assert(word != 0);
+
+	return __builtin_ctz(word);
 #elif defined(_MSC_VER)
-	const unsigned long orig_word = word;
-	unsigned long bitscan_result;
+	unsigned long result;
 	bool		non_zero;
-#endif
 
-#if !defined(HAVE_BITSCAN_FORWARD) || defined(USE_ASSERT_CHECKING)
+	non_zero = _BitScanForward(&result, word);
+	Assert(non_zero);
+	return (int) result;
+#else
 	int			result = 0;
 
 	Assert(word != 0);
@@ -152,22 +130,8 @@ pg_rightmost_one_pos32(uint32 word)
 		result += 8;
 	}
 	result += pg_rightmost_one_pos[word & 255];
-#endif
-
-#ifdef HAVE_BITSCAN_FORWARD
-
-#if defined(HAVE__BUILTIN_CTZ)
-	bitscan_result = __builtin_ctz(orig_word);
-#elif defined(_MSC_VER)
-	non_zero = _BitScanForward(&bitscan_result, orig_word);
-	Assert(non_zero);
-#endif
-	Assert(bitscan_result == result);
-	return bitscan_result;
-
-#else
 	return result;
-#endif							/* HAVE_BITSCAN_FORWARD */
+#endif							/* HAVE__BUILTIN_CTZ */
 }
 
 /*
@@ -178,15 +142,24 @@ static inline int
 pg_rightmost_one_pos64(uint64 word)
 {
 #ifdef HAVE__BUILTIN_CTZ
-	const uint64 orig_word = word;
-	int			bitscan_result;
+	Assert(word != 0);
+
+#if defined(HAVE_LONG_INT_64)
+	return __builtin_ctzl(word);
+#elif defined(HAVE_LONG_LONG_INT_64)
+	return __builtin_ctzll(word);
+#else
+#error must have a working 64-bit integer datatype
+#endif							/* HAVE_LONG_INT_64 */
+
 #elif defined(_MSC_VER)
-	const unsigned __int64 orig_word = word;
-	unsigned long bitscan_result;
+	unsigned long result;
 	bool		non_zero;
-#endif
 
-#if !defined(HAVE_BITSCAN_FORWARD) || defined(USE_ASSERT_CHECKING)
+	non_zero = _BitScanForward64(&result, word);
+	Assert(non_zero);
+	return (int) result;
+#else
 	int			result = 0;
 
 	Assert(word != 0);
@@ -197,29 +170,8 @@ pg_rightmost_one_pos64(uint64 word)
 		result += 8;
 	}
 	result += pg_rightmost_one_pos[word & 255];
-#endif
-
-#ifdef HAVE_BITSCAN_FORWARD
-
-#if defined(HAVE__BUILTIN_CTZ)
-#if defined(HAVE_LONG_INT_64)
-	bitscan_result = __builtin_ctzl(orig_word);
-#elif defined(HAVE_LONG_LONG_INT_64)
-	bitscan_result = __builtin_ctzll(orig_word);
-#else
-#error must have a working 64-bit integer datatype
-#endif							/* HAVE_LONG_INT_64 */
-
-#elif defined(_MSC_VER)
-	non_zero = _BitScanForward64(&bitscan_result, orig_word);
-	Assert(non_zero);
-#endif							/* HAVE__BUILTIN_CTZ */
-	Assert(bitscan_result == result);
-	return bitscan_result;
-
-#else
 	return result;
-#endif							/* HAVE_BITSCAN_FORWARD */
+#endif							/* HAVE__BUILTIN_CTZ */
 }
 
 /*