Introduced a SPL inline function (multiple-accumulate), for preformance in ARMv7.

It's used in quite some occations over many modules.
Review URL: http://webrtc-codereview.appspot.com/178004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@691 4adac7df-926f-26a2-2b94-8c16560cd09d

src/common_audio/signal_processing_library/main/interface/signal_processing_library.h

@@ -1670,6 +1670,19 @@ void WebRtcSpl_SynthesisQMF(const WebRtc_Word16* low_band,
 //      - out16     : the saturated 16-bit word.
 //
 
+// int32_t WebRtc_MulAccumW16(...)
+//
+// This function multiply a 16-bit word by a 16-bit word, and accumulate this
+// value to a 32-bit integer.
+// 
+// Input:
+//      - a    : The value of the first 16-bit word.
+//      - b    : The value of the second 16-bit word.
+//      - c    : The value of an 32-bit integer.
+//
+// Return Value: The value of a * b + c.
+//
+
 // WebRtc_Word16 WebRtcSpl_get_version(...)
 //
 // This function gives the version string of the Signal Processing Library.

src/common_audio/signal_processing_library/main/interface/spl_inl.h

@@ -148,6 +148,12 @@ static __inline int WebRtcSpl_NormW16(WebRtc_Word16 a) {
   return zeros;
 }
 
+static __inline int32_t WebRtc_MulAccumW16(int16_t a,
+                                          int16_t b,
+                                          int32_t c) {
+  return (a * b + c);
+}
+
 #endif  // WEBRTC_ARCH_ARM_V7A
 
 #endif  // WEBRTC_SPL_SPL_INL_H_

src/common_audio/signal_processing_library/main/interface/spl_inl_armv7.h

@@ -45,6 +45,14 @@ static __inline WebRtc_Word32 WEBRTC_SPL_MUL_16_16(WebRtc_Word16 a,
   return tmp;
 }
 
+static __inline int32_t WebRtc_MulAccumW16(int16_t a,
+                                          int16_t b,
+                                          int32_t c) {
+  int32_t tmp = 0;
+  __asm__("smlabb %0, %1, %2, %3":"=r"(tmp):"r"(a), "r"(b), "r"(c));
+  return tmp;
+}
+
 static __inline WebRtc_Word16 WebRtcSpl_AddSatW16(WebRtc_Word16 a,
                                                   WebRtc_Word16 b) {
   WebRtc_Word32 s_sum;