@@ -222,6 +222,56 @@ static inline uint64_t extract64(uint64_t value, int start, int length)
}
/**
+ * sextract32:
+ * @value: the value to extract the bit field from
+ * @start: the lowest bit in the bit field (numbered from 0)
+ * @length: the length of the bit field
+ *
+ * Extract from the 32 bit input @value the bit field specified by the
+ * @start and @length parameters, and return it, sign extended to
+ * an int32_t (ie with the most significant bit of the field propagated
+ * to all the upper bits of the return value). The bit field must lie
+ * entirely within the 32 bit word. It is valid to request that
+ * all 32 bits are returned (ie @length 32 and @start 0).
+ *
+ * Returns: the sign extended value of the bit field extracted from the
+ * input value.
+ */
+static inline int32_t sextract32(uint32_t value, int start, int length)
+{
+ assert(start >= 0 && length > 0 && length <= 32 - start);
+ /* Note that this implementation relies on right shift of signed
+ * integers being an arithmetic shift.
+ */
+ return ((int32_t)(value << (32 - length - start))) >> (32 - length);
+}
+
+/**
+ * sextract64:
+ * @value: the value to extract the bit field from
+ * @start: the lowest bit in the bit field (numbered from 0)
+ * @length: the length of the bit field
+ *
+ * Extract from the 64 bit input @value the bit field specified by the
+ * @start and @length parameters, and return it, sign extended to
+ * an int64_t (ie with the most significant bit of the field propagated
+ * to all the upper bits of the return value). The bit field must lie
+ * entirely within the 64 bit word. It is valid to request that
+ * all 64 bits are returned (ie @length 64 and @start 0).
+ *
+ * Returns: the sign extended value of the bit field extracted from the
+ * input value.
+ */
+static inline uint64_t sextract64(uint64_t value, int start, int length)
+{
+ assert(start >= 0 && length > 0 && length <= 64 - start);
+ /* Note that this implementation relies on right shift of signed
+ * integers being an arithmetic shift.
+ */
+ return ((int64_t)(value << (64 - length - start))) >> (64 - length);
+}
+
+/**
* deposit32:
* @value: initial value to insert bit field into
* @start: the lowest bit in the bit field (numbered from 0)
A common operation in instruction decoding is to take a field from an instruction that represents a signed integer in some arbitrary number of bits, and sign extend it into a C signed integer type for manipulation. Provide new functions sextract32() and sextract64() which perform this operation; they are like the existing extract32() and extract64() except that the field is sign-extended into the returned result. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- include/qemu/bitops.h | 50 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+)