Diff: src/Cortex-M4-M3/BasicMathFunctions/arm_shift_q15.c

Revision:

0:1014af42efd9

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Cortex-M4-M3/BasicMathFunctions/arm_shift_q15.c	Thu Mar 10 15:07:50 2011 +0000
@@ -0,0 +1,152 @@
+/* ----------------------------------------------------------------------  
+* Copyright (C) 2010 ARM Limited. All rights reserved.  
+*  
+* $Date:        29. November 2010  
+* $Revision: 	V1.0.3  
+*  
+* Project: 	    CMSIS DSP Library  
+* Title:		arm_shift_q15.c  
+*  
+* Description:	Shifts elements of a Q15 vector a specified number of bits.  
+*  
+* Target Processor: Cortex-M4/Cortex-M3
+*  
+* Version 1.0.3 2010/11/29 
+*    Re-organized the CMSIS folders and updated documentation.  
+*   
+* Version 1.0.2 2010/11/11  
+*    Documentation updated.   
+*  
+* Version 1.0.1 2010/10/05   
+*    Production release and review comments incorporated.  
+*  
+* Version 1.0.0 2010/09/20   
+*    Production release and review comments incorporated.  
+*  
+* Version 0.0.7  2010/06/10   
+*    Misra-C changes done  
+* -------------------------------------------------------------------- */ 
+ 
+#include "arm_math.h" 
+ 
+/**  
+ * @ingroup groupMath  
+ */ 
+ 
+/**  
+ * @addtogroup shift  
+ * @{  
+ */ 
+ 
+/**  
+ * @brief  Shifts the elements of a Q15 vector a specified number of bits.  
+ * @param  *pSrc points to the input vector  
+ * @param  shiftBits number of bits to shift.  A positive value shifts left; a negative value shifts right.  
+ * @param  *pDst points to the output vector  
+ * @param  blockSize number of samples in the vector  
+ * @return none.  
+ *  
+ * <b>Scaling and Overflow Behavior:</b>  
+ * \par  
+ * The function uses saturating arithmetic.  
+ * Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.  
+ */ 
+ 
+void arm_shift_q15( 
+  q15_t * pSrc, 
+  int8_t shiftBits, 
+  q15_t * pDst, 
+  uint32_t blockSize) 
+{ 
+  uint32_t blkCnt;                               /* loop counter */ 
+  uint8_t sign;                                  /* Sign of shiftBits */ 
+  q15_t in1, in2;                                /* Temporary variables */ 
+ 
+ 
+  /*loop Unrolling */ 
+  blkCnt = blockSize >> 2u; 
+ 
+  /* Getting the sign of shiftBits */ 
+  sign = (shiftBits & 0x80); 
+ 
+  /* If the shift value is positive then do right shift else left shift */ 
+  if(sign == 0u) 
+  { 
+    /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
+     ** a second loop below computes the remaining 1 to 3 samples. */ 
+    while(blkCnt > 0u) 
+    { 
+      /* Read 2 inputs */ 
+      in1 = *pSrc++; 
+      in2 = *pSrc++; 
+      /* C = A << shiftBits */ 
+      /* Shift the inputs and then store the results in the destination buffer. */ 
+      *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16), 
+                                  __SSAT((in2 << shiftBits), 16), 16); 
+ 
+      in1 = *pSrc++; 
+      in2 = *pSrc++; 
+ 
+      *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16), 
+                                  __SSAT((in2 << shiftBits), 16), 16); 
+ 
+      /* Decrement the loop counter */ 
+      blkCnt--; 
+    } 
+ 
+    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
+     ** No loop unrolling is used. */ 
+    blkCnt = blockSize % 0x4u; 
+ 
+    while(blkCnt > 0u) 
+    { 
+      /* C = A << shiftBits */ 
+      /* Shift and then store the results in the destination buffer. */ 
+      *pDst++ = __SSAT((*pSrc++ << shiftBits), 16); 
+ 
+      /* Decrement the loop counter */ 
+      blkCnt--; 
+    } 
+  } 
+  else 
+  { 
+    /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
+     ** a second loop below computes the remaining 1 to 3 samples. */ 
+    while(blkCnt > 0u) 
+    { 
+      /* Read 2 inputs */ 
+      in1 = *pSrc++; 
+      in2 = *pSrc++; 
+      /* C = A >> shiftBits */ 
+      /* Shift the inputs and then store the results in the destination buffer. */ 
+      *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits), 
+                                  (in2 >> -shiftBits), 16); 
+      in1 = *pSrc++; 
+      in2 = *pSrc++; 
+ 
+      *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits), 
+                                  (in2 >> -shiftBits), 16); 
+ 
+      /* Decrement the loop counter */ 
+      blkCnt--; 
+    } 
+ 
+    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
+     ** No loop unrolling is used. */ 
+    blkCnt = blockSize % 0x4u; 
+ 
+    while(blkCnt > 0u) 
+    { 
+      /* C = A >> shiftBits */ 
+      /* Shift the inputs and then store the results in the destination buffer. */ 
+      *pDst++ = (*pSrc++ >> -shiftBits); 
+ 
+      /* Decrement the loop counter */ 
+      blkCnt--; 
+    } 
+  } 
+} 
+ 
+/**  
+ * @} end of shift group  
+ */