RE: [RFC 2/7] eal: add generic bit manipulation macros

[Heng Wang <heng.wang@ericsson.com>]

Hi Mattias,
  I have a comment about the _Generic. What if the user gives uint8_t * or uint16_t * as the address. One improvement is that we could add a default branch in _Generic to throw a compiler error or assert false.
  Another question is what if nr >= sizeof(type) ? What if you do, for example, (uint32_t)1 << 35? Maybe we could add an assert in the implementation?

Regards,
Heng

-----Original Message-----
From: Mattias Rönnblom <mattias.ronnblom@ericsson.com> 
Sent: Saturday, March 2, 2024 2:53 PM
To: dev@dpdk.org
Cc: hofors@lysator.liu.se; Heng Wang <heng.wang@ericsson.com>; Mattias Rönnblom <mattias.ronnblom@ericsson.com>
Subject: [RFC 2/7] eal: add generic bit manipulation macros

Add bit-level test/set/clear/assign macros operating on both 32-bit and 64-bit words by means of C11 generic selection.

Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
---
 lib/eal/include/rte_bitops.h | 81 ++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

diff --git a/lib/eal/include/rte_bitops.h b/lib/eal/include/rte_bitops.h index 9a368724d5..afd0f11033 100644
--- a/lib/eal/include/rte_bitops.h
+++ b/lib/eal/include/rte_bitops.h
@@ -107,6 +107,87 @@ extern "C" {
 #define RTE_FIELD_GET64(mask, reg) \
 		((typeof(mask))(((reg) & (mask)) >> rte_ctz64(mask)))
 
+/**
+ * Test bit in word.
+ *
+ * Generic selection macro to test the value of a bit in a 32-bit or
+ * 64-bit word. The type of operation depends on the type of the @c
+ * addr parameter.
+ *
+ * This macro does not give any guarantees in regards to memory
+ * ordering or atomicity.
+ *
+ * @param addr
+ *   A pointer to the word to modify.
+ * @param nr
+ *   The index of the bit.
+ */
+#define rte_bit_test(addr, nr)				\
+	_Generic((addr),				\
+		 uint32_t *: rte_bit_test32,		\
+		 uint64_t *: rte_bit_test64)(addr, nr)
+
+/**
+ * Set bit in word.
+ *
+ * Generic selection macro to set a bit in a 32-bit or 64-bit
+ * word. The type of operation depends on the type of the @c addr
+ * parameter.
+ *
+ * This macro does not give any guarantees in regards to memory
+ * ordering or atomicity.
+ *
+ * @param addr
+ *   A pointer to the word to modify.
+ * @param nr
+ *   The index of the bit.
+ */
+#define rte_bit_set(addr, nr)				\
+	_Generic((addr),				\
+		 uint32_t *: rte_bit_set32,		\
+		 uint64_t *: rte_bit_set64)(addr, nr)
+
+/**
+ * Clear bit in word.
+ *
+ * Generic selection macro to clear a bit in a 32-bit or 64-bit
+ * word. The type of operation depends on the type of the @c addr
+ * parameter.
+ *
+ * This macro does not give any guarantees in regards to memory
+ * ordering or atomicity.
+ *
+ * @param addr
+ *   A pointer to the word to modify.
+ * @param nr
+ *   The index of the bit.
+ */
+#define rte_bit_clear(addr, nr)			\
+	_Generic((addr),				\
+		 uint32_t *: rte_bit_clear32,		\
+		 uint64_t *: rte_bit_clear64)(addr, nr)
+
+/**
+ * Assign a value to a bit in word.
+ *
+ * Generic selection macro to assign a value to a bit in a 32-bit or 
+64-bit
+ * word. The type of operation depends on the type of the @c addr parameter.
+ *
+ * This macro does not give any guarantees in regards to memory
+ * ordering or atomicity.
+ *
+ * @param addr
+ *   A pointer to the word to modify.
+ * @param nr
+ *   The index of the bit.
+ * @param value
+ *   The new value of the bit - true for '1', or false for '0'.
+ */
+#define rte_bit_assign(addr, nr, value)			\
+	_Generic((addr),				\
+		 uint32_t *: rte_bit_assign32,			\
+		 uint64_t *: rte_bit_assign64)(addr, nr, value)
+
 /**
  * Test if a particular bit in a 32-bit word is set.
  *
--
2.34.1