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[PULL,v2,04/12] qemu/host-utils.h: Add clz and ctz functions for lower-bit integers

Message ID 20230503072221.1746802-8-richard.henderson@linaro.org
State New
Headers show
Series tcg: Build once for system, once for user | expand

Commit Message

Richard Henderson May 3, 2023, 7:20 a.m. UTC
From: Kiran Ostrolenk <kiran.ostrolenk@codethink.co.uk>

This is for use in the RISC-V vclz and vctz instructions (implemented in
proceeding commit).

Signed-off-by: Kiran Ostrolenk <kiran.ostrolenk@codethink.co.uk>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230428144757.57530-11-lawrence.hunter@codethink.co.uk>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/qemu/host-utils.h | 54 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
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Patch

diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index 3ce62bf4a5..d3b4dce6a9 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -107,6 +107,36 @@  static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
 }
 #endif
 
+/**
+ * clz8 - count leading zeros in a 8-bit value.
+ * @val: The value to search
+ *
+ * Returns 8 if the value is zero.  Note that the GCC builtin is
+ * undefined if the value is zero.
+ *
+ * Note that the GCC builtin will upcast its argument to an `unsigned int`
+ * so this function subtracts off the number of prepended zeroes.
+ */
+static inline int clz8(uint8_t val)
+{
+    return val ? __builtin_clz(val) - 24 : 8;
+}
+
+/**
+ * clz16 - count leading zeros in a 16-bit value.
+ * @val: The value to search
+ *
+ * Returns 16 if the value is zero.  Note that the GCC builtin is
+ * undefined if the value is zero.
+ *
+ * Note that the GCC builtin will upcast its argument to an `unsigned int`
+ * so this function subtracts off the number of prepended zeroes.
+ */
+static inline int clz16(uint16_t val)
+{
+    return val ? __builtin_clz(val) - 16 : 16;
+}
+
 /**
  * clz32 - count leading zeros in a 32-bit value.
  * @val: The value to search
@@ -153,6 +183,30 @@  static inline int clo64(uint64_t val)
     return clz64(~val);
 }
 
+/**
+ * ctz8 - count trailing zeros in a 8-bit value.
+ * @val: The value to search
+ *
+ * Returns 8 if the value is zero.  Note that the GCC builtin is
+ * undefined if the value is zero.
+ */
+static inline int ctz8(uint8_t val)
+{
+    return val ? __builtin_ctz(val) : 8;
+}
+
+/**
+ * ctz16 - count trailing zeros in a 16-bit value.
+ * @val: The value to search
+ *
+ * Returns 16 if the value is zero.  Note that the GCC builtin is
+ * undefined if the value is zero.
+ */
+static inline int ctz16(uint16_t val)
+{
+    return val ? __builtin_ctz(val) : 16;
+}
+
 /**
  * ctz32 - count trailing zeros in a 32-bit value.
  * @val: The value to search