From 02fed471a4568852d6618e041c4f2af0d7730ee2 Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jmvalin@jmvalin.ca>
Date: Thu, 29 Aug 2013 15:29:02 -0400
Subject: Implements fixed-point silk_LPC_analysis_filter() in terms of
 celt_fir()

Saves 2.5% on ARM without any asm. The float build still uses the old
code because celt_fir() then becomes a float function.
---
 celt/arch.h                |  1 +
 celt/celt_lpc.c            | 13 ++++++-------
 celt/fixed_generic.h       |  2 ++
 silk/LPC_analysis_filter.c | 23 ++++++++++++++++++++++-
 4 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/celt/arch.h b/celt/arch.h
index e497a4d9..78e2635f 100644
--- a/celt/arch.h
+++ b/celt/arch.h
@@ -163,6 +163,7 @@ typedef float celt_ener;
 #define SHR(a,shift)    (a)
 #define SHL(a,shift)    (a)
 #define SATURATE(x,a)   (x)
+#define SATURATE16(x)   (x)
 
 #define ROUND16(a,shift)  (a)
 #define HALF16(x)       (.5f*(x))
diff --git a/celt/celt_lpc.c b/celt/celt_lpc.c
index 523c36aa..7ffe90a3 100644
--- a/celt/celt_lpc.c
+++ b/celt/celt_lpc.c
@@ -118,25 +118,24 @@ void celt_fir(const opus_val16 *_x,
       {
          sum = MAC16_16(sum,rnum[j],x[i+j]);
       }
-      _y[i] = ROUND16(sum, SIG_SHIFT);
+      _y[i] = SATURATE16(PSHR32(sum, SIG_SHIFT));
    }
 #else
-   celt_assert((ord&3)==0);
    for (i=0;i<N-3;i+=4)
    {
       opus_val32 sum[4]={0,0,0,0};
       xcorr_kernel(rnum, x+i, sum, ord);
-      _y[i  ] = ADD16(_x[i  ], ROUND16(sum[0], SIG_SHIFT));
-      _y[i+1] = ADD16(_x[i+1], ROUND16(sum[1], SIG_SHIFT));
-      _y[i+2] = ADD16(_x[i+2], ROUND16(sum[2], SIG_SHIFT));
-      _y[i+3] = ADD16(_x[i+3], ROUND16(sum[3], SIG_SHIFT));
+      _y[i  ] = SATURATE16(ADD32(EXTEND32(_x[i  ]), PSHR32(sum[0], SIG_SHIFT)));
+      _y[i+1] = SATURATE16(ADD32(EXTEND32(_x[i+1]), PSHR32(sum[1], SIG_SHIFT)));
+      _y[i+2] = SATURATE16(ADD32(EXTEND32(_x[i+2]), PSHR32(sum[2], SIG_SHIFT)));
+      _y[i+3] = SATURATE16(ADD32(EXTEND32(_x[i+3]), PSHR32(sum[3], SIG_SHIFT)));
    }
    for (;i<N;i++)
    {
       opus_val32 sum = 0;
       for (j=0;j<ord;j++)
          sum = MAC16_16(sum,rnum[j],x[i+j]);
-      _y[i] = ADD16(_x[i  ], ROUND16(sum, SIG_SHIFT));
+      _y[i] = SATURATE16(ADD32(EXTEND32(_x[i]), PSHR32(sum, SIG_SHIFT)));
    }
 #endif
    RESTORE_STACK;
diff --git a/celt/fixed_generic.h b/celt/fixed_generic.h
index ac01a434..0e77976e 100644
--- a/celt/fixed_generic.h
+++ b/celt/fixed_generic.h
@@ -84,6 +84,8 @@
 #define PSHR(a,shift) (SHR((a)+((EXTEND32(1)<<((shift))>>1)),shift))
 #define SATURATE(x,a) (((x)>(a) ? (a) : (x)<-(a) ? -(a) : (x)))
 
+#define SATURATE16(x) (EXTRACT16((x)>32767 ? 32767 : (x)<-32768 ? -32768 : (x)))
+
 /** Shift by a and round-to-neareast 32-bit value. Result is a 16-bit value */
 #define ROUND16(x,a) (EXTRACT16(PSHR32((x),(a))))
 /** Divide by two */
diff --git a/silk/LPC_analysis_filter.c b/silk/LPC_analysis_filter.c
index e2c0c88b..9bfeba0f 100644
--- a/silk/LPC_analysis_filter.c
+++ b/silk/LPC_analysis_filter.c
@@ -30,6 +30,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #endif
 
 #include "SigProc_FIX.h"
+#include "celt_lpc.h"
 
 /*******************************************/
 /* LPC analysis filter                     */
@@ -46,14 +47,33 @@ void silk_LPC_analysis_filter(
     const opus_int32            d                   /* I    Filter order                                                */
 )
 {
-    opus_int         ix, j;
+    opus_int   j;
+#ifdef FIXED_POINT
+    opus_int16 mem[SILK_MAX_ORDER_LPC];
+    opus_int16 num[SILK_MAX_ORDER_LPC];
+#else
+    int ix;
     opus_int32       out32_Q12, out32;
     const opus_int16 *in_ptr;
+#endif
 
     silk_assert( d >= 6 );
     silk_assert( (d & 1) == 0 );
     silk_assert( d <= len );
 
+#ifdef FIXED_POINT
+    silk_assert( d <= SILK_MAX_ORDER_LPC );
+    for ( j = 0; j < d; j++ ) {
+        num[ j ] = -B[ j ];
+    }
+    for (j=0;j<d;j++) {
+        mem[ j ] = in[ d - j - 1 ];
+    }
+    celt_fir( in + d, num, out + d, len - d, d, mem );
+    for ( j = 0; j < d; j++ ) {
+        out[ j ] = 0;
+    }
+#else
     for( ix = d; ix < len; ix++ ) {
         in_ptr = &in[ ix - 1 ];
 
@@ -82,4 +102,5 @@ void silk_LPC_analysis_filter(
 
     /* Set first d output samples to zero */
     silk_memset( out, 0, d * sizeof( opus_int16 ) );
+#endif
 }
-- 
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