Audio: Use generic saturation logic for improved efficiency

This check-in refactors saturation functions to use bitwise
operations for handling overflow and underflow, improving efficiency.

- Replaced if-else checks with bitwise masks to handle overflow and
  underflow for int32, int24, int16, and int8 saturation functions.

- For each bit width, created masks by shifting the results of comparisons
  (x - MIN_VAL) and (MAX_VAL - x) to the respective overflow/underflow
  detection bits.

- Mask >> 31 or >> 63 results in either 0 (no overflow/underflow) or -1
  (overflow/underflow occurred).

- Applied bitwise operations to conditionally replace original values
  with boundary values (MIN or MAX) based on the computed masks.

- This approach avoids branching, improves efficiency, and ensures
  accurate saturation within specified bit-width limits.

Signed-off-by: Shriram Shastry <[email protected]>

src/include/sof/audio/format_generic.h

@@ -1,6 +1,8 @@
 /* SPDX-License-Identifier: BSD-3-Clause
  *
  * Copyright(c) 2021 Intel Corporation. All rights reserved.
+ *
+ * Author: Shriram Shastry <[email protected]>
  */
 
 #ifndef __SOF_AUDIO_FORMAT_GENERIC_H__
@@ -9,45 +11,85 @@
 #include <stdint.h>
 
 /* Saturation inline functions */
-
+/**
+ * @brief Saturate an int64_t value to fit within the range of int32_t.
+ *
+ * This function ensures that the input value 'x' fits within the range of
+ * int32_t. If 'x' exceeds this range, it will be bound to INT32_MAX or INT32_MIN
+ * accordingly.
+ *
+ * @param x The input value to saturate.
+ * @return int32_t The saturated int32_t value.
+ */
 static inline int32_t sat_int32(int64_t x)
 {
-	if (x > INT32_MAX)
-		return INT32_MAX;
-	else if (x < INT32_MIN)
-		return INT32_MIN;
-	else
-		return (int32_t)x;
+	int64_t mask_overflow = (INT32_MAX - x) >> 63;
+	int64_t mask_underflow = (x - INT32_MIN) >> 63;
+
+	x = (x & ~mask_overflow) | (INT32_MAX & mask_overflow);
+	x = (x & ~mask_underflow) | (INT32_MIN & mask_underflow);
+	return (int32_t)x;
+
 }
 
+/**
+ * @brief Saturate an int32_t value to fit within the range of a 24-bit integer.
+ *
+ * This function ensures that the input value 'x' fits within the range of a
+ * 24-bit integer. If 'x' exceeds this range, it will be bound to INT24_MAXVALUE
+ * or INT24_MINVALUE accordingly.
+ *
+ * @param x The input value to saturate.
+ * @return int32_t The saturated int32_t value.
+ */
 static inline int32_t sat_int24(int32_t x)
 {
-	if (x > INT24_MAXVALUE)
-		return INT24_MAXVALUE;
-	else if (x < INT24_MINVALUE)
-		return INT24_MINVALUE;
-	else
-		return x;
+	int32_t mask_overflow = (INT24_MAXVALUE - x) >> 31;
+	int32_t mask_underflow = (x - INT24_MINVALUE) >> 31;
+
+	x = (x & ~mask_overflow) | (INT24_MAXVALUE & mask_overflow);
+	x = (x & ~mask_underflow) | (INT24_MINVALUE & mask_underflow);
+	return x;
 }
 
+/**
+ * @brief Saturate an int32_t value to fit within the range of a 16-bit integer.
+ *
+ * This function ensures that the input value 'x' fits within the range of a
+ * 16-bit integer. If 'x' exceeds this range, it will be bound to INT16_MAX or INT16_MIN
+ * accordingly.
+ *
+ * @param x The input value to saturate.
+ * @return int16_t The saturated int16_t value.
+ */
 static inline int16_t sat_int16(int32_t x)
 {
-	if (x > INT16_MAX)
-		return INT16_MAX;
-	else if (x < INT16_MIN)
-		return INT16_MIN;
-	else
-		return (int16_t)x;
+	int32_t mask_overflow = (INT16_MAX - x) >> 31;
+	int32_t mask_underflow = (x - INT16_MIN) >> 31;
+
+	x = (x & ~mask_overflow) | (INT16_MAX & mask_overflow);
+	x = (x & ~mask_underflow) | (INT16_MIN & mask_underflow);
+	return (int16_t)x;
 }
 
+/**
+ * @brief Saturate an int32_t value to fit within the range of an 8-bit integer.
+ *
+ * This function ensures that the input value 'x' fits within the range of an
+ * 8-bit integer. If 'x' exceeds this range, it will be bound to INT8_MAX or INT8_MIN
+ * accordingly.
+ *
+ * @param x The input value to saturate.
+ * @return int8_t The saturated int8_t value.
+ */
 static inline int8_t sat_int8(int32_t x)
 {
-	if (x > INT8_MAX)
-		return INT8_MAX;
-	else if (x < INT8_MIN)
-		return INT8_MIN;
-	else
-		return (int8_t)x;
+	int32_t mask_overflow = (INT8_MAX - x) >> 31;
+	int32_t mask_underflow = (x - INT8_MIN) >> 31;
+
+	x = (x & ~mask_overflow) | (INT8_MAX & mask_overflow);
+	x = (x & ~mask_underflow) | (INT8_MIN & mask_underflow);
+	return (int8_t)x;
 }
 
 #endif /* __SOF_AUDIO_FORMAT_GENERIC_H__ */