hw/audio/cs4231a: skip automatic zero-init of large arrays

The 'cs_write_audio' method has a pair of byte arrays, one 4k in size
and one 8k, which are used in converting audio samples. Skip the
automatic zero-init of these arrays to eliminate the performance
overhead in the I/O hot path.

The 'tmpbuf' array will be fully initialized when reading a block of
data from the guest. The 'linbuf' array will be fully initialized
when converting the audio samples.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20250610123709.835102-9-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/hw/audio/cs4231a.c b/hw/audio/cs4231a.c
index eb9a45805b758ffbf731f0261b640d28e3f96284..6dfff202ff924c4ad53a7dbe6af47222f5705ef7 100644 (file)
--- a/hw/audio/cs4231a.c
+++ b/hw/audio/cs4231a.c
@@ -528,7 +528,7 @@ static int cs_write_audio (CSState *s, int nchan, int dma_pos,
                            int dma_len, int len)
 {
     int temp, net;
-    uint8_t tmpbuf[4096];
+    QEMU_UNINITIALIZED uint8_t tmpbuf[4096];
     IsaDmaClass *k = ISADMA_GET_CLASS(s->isa_dma);
 
     temp = len;
@@ -547,7 +547,7 @@ static int cs_write_audio (CSState *s, int nchan, int dma_pos,
         copied = k->read_memory(s->isa_dma, nchan, tmpbuf, dma_pos, to_copy);
         if (s->tab) {
             int i;
-            int16_t linbuf[4096];
+            QEMU_UNINITIALIZED int16_t linbuf[4096];
 
             for (i = 0; i < copied; ++i)
                 linbuf[i] = s->tab[tmpbuf[i]];