Optimize decompression speed for gcc and clang (#1892)
* Optimize `ZSTD_decodeSequence()`
* Optimize Huffman decoding
* Optimize `ZSTD_decompressSequences()`
* Delete `ZSTD_decodeSequenceLong()`
diff --git a/lib/common/bitstream.h b/lib/common/bitstream.h
index 1c294b8..fe3148e 100644
--- a/lib/common/bitstream.h
+++ b/lib/common/bitstream.h
@@ -48,6 +48,7 @@
* Dependencies
******************************************/
#include "mem.h" /* unaligned access routines */
+#include "compiler.h" /* UNLIKELY() */
#include "debug.h" /* assert(), DEBUGLOG(), RAWLOG() */
#include "error_private.h" /* error codes and messages */
@@ -411,6 +412,23 @@
return value;
}
+/*! BIT_reloadDStreamFast() :
+ * Similar to BIT_reloadDStream(), but with two differences:
+ * 1. bitsConsumed <= sizeof(bitD->bitContainer)*8 must hold!
+ * 2. Returns BIT_DStream_overflow when bitD->ptr < bitD->limitPtr, at this
+ * point you must use BIT_reloadDStream() to reload.
+ */
+MEM_STATIC BIT_DStream_status BIT_reloadDStreamFast(BIT_DStream_t* bitD)
+{
+ if (UNLIKELY(bitD->ptr < bitD->limitPtr))
+ return BIT_DStream_overflow;
+ assert(bitD->bitsConsumed <= sizeof(bitD->bitContainer)*8);
+ bitD->ptr -= bitD->bitsConsumed >> 3;
+ bitD->bitsConsumed &= 7;
+ bitD->bitContainer = MEM_readLEST(bitD->ptr);
+ return BIT_DStream_unfinished;
+}
+
/*! BIT_reloadDStream() :
* Refill `bitD` from buffer previously set in BIT_initDStream() .
* This function is safe, it guarantees it will not read beyond src buffer.
@@ -422,10 +440,7 @@
return BIT_DStream_overflow;
if (bitD->ptr >= bitD->limitPtr) {
- bitD->ptr -= bitD->bitsConsumed >> 3;
- bitD->bitsConsumed &= 7;
- bitD->bitContainer = MEM_readLEST(bitD->ptr);
- return BIT_DStream_unfinished;
+ return BIT_reloadDStreamFast(bitD);
}
if (bitD->ptr == bitD->start) {
if (bitD->bitsConsumed < sizeof(bitD->bitContainer)*8) return BIT_DStream_endOfBuffer;