Revert "unlzma: speedup, by Pascal Bellard (pascal.bellard AT ads-lu.com)"

https://bugs.busybox.net/show_bug.cgi?id=599

This reverts commit 9ac3dc764a78b51fe8fdcd1b4682850de098733b.

2 files changed, 98 insertions, 60 deletions

diff --git a/archival/Config.in b/archival/Config.in
index cae7f20bb..71b953819 100644
--- a/archival/Config.in
+++ b/archival/Config.in
@@ -298,8 +298,8 @@ config FEATURE_LZMA_FAST
 	default n
 	depends on UNLZMA
 	help
-	  This option reduces decompression time by about 25% at the cost of
-	  a 1K bigger binary.
+	  This option reduces decompression time by about 33% at the cost of
+	  a 2K bigger binary.
 
 config UNZIP
 	bool "unzip"
diff --git a/archival/libunarchive/decompress_unlzma.c b/archival/libunarchive/decompress_unlzma.c
index 68085d68c..33e5cd65d 100644
--- a/archival/libunarchive/decompress_unlzma.c
+++ b/archival/libunarchive/decompress_unlzma.c
@@ -8,15 +8,14 @@
  *
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
+
 #include "libbb.h"
 #include "unarchive.h"
 
 #if ENABLE_FEATURE_LZMA_FAST
 #  define speed_inline ALWAYS_INLINE
-#  define size_inline
 #else
 #  define speed_inline
-#  define size_inline ALWAYS_INLINE
 #endif
 
 
@@ -45,8 +44,8 @@ typedef struct {
 #define RC_MODEL_TOTAL_BITS 11
 
 
-/* Called twice: once at startup (LZMA_FAST only) and once in rc_normalize() */
-static size_inline void rc_read(rc_t *rc)
+/* Called twice: once at startup and once in rc_normalize() */
+static void rc_read(rc_t *rc)
 {
 	int buffer_size = safe_read(rc->fd, RC_BUFFER, RC_BUFFER_SIZE);
 	if (buffer_size <= 0)
@@ -55,17 +54,8 @@ static size_inline void rc_read(rc_t *rc)
 	rc->buffer_end = RC_BUFFER + buffer_size;
 }
 
-/* Called twice, but one callsite is in speed_inline'd rc_is_bit_1() */
-static void rc_do_normalize(rc_t *rc)
-{
-	if (rc->ptr >= rc->buffer_end)
-		rc_read(rc);
-	rc->range <<= 8;
-	rc->code = (rc->code << 8) | *rc->ptr++;
-}
-
 /* Called once */
-static ALWAYS_INLINE rc_t* rc_init(int fd) /*, int buffer_size) */
+static rc_t* rc_init(int fd) /*, int buffer_size) */
 {
 	int i;
 	rc_t *rc;
@@ -73,18 +63,17 @@ static ALWAYS_INLINE rc_t* rc_init(int fd) /*, int buffer_size) */
 	rc = xmalloc(sizeof(*rc) + RC_BUFFER_SIZE);
 
 	rc->fd = fd;
+	/* rc->buffer_size = buffer_size; */
+	rc->buffer_end = RC_BUFFER + RC_BUFFER_SIZE;
 	rc->ptr = rc->buffer_end;
 
+	rc->code = 0;
+	rc->range = 0xFFFFFFFF;
 	for (i = 0; i < 5; i++) {
-#if ENABLE_FEATURE_LZMA_FAST
 		if (rc->ptr >= rc->buffer_end)
 			rc_read(rc);
 		rc->code = (rc->code << 8) | *rc->ptr++;
-#else
-		rc_do_normalize(rc);
-#endif
 	}
-	rc->range = 0xFFFFFFFF;
 	return rc;
 }
 
@@ -94,6 +83,14 @@ static ALWAYS_INLINE void rc_free(rc_t *rc)
 	free(rc);
 }
 
+/* Called twice, but one callsite is in speed_inline'd rc_is_bit_0_helper() */
+static void rc_do_normalize(rc_t *rc)
+{
+	if (rc->ptr >= rc->buffer_end)
+		rc_read(rc);
+	rc->range <<= 8;
+	rc->code = (rc->code << 8) | *rc->ptr++;
+}
 static ALWAYS_INLINE void rc_normalize(rc_t *rc)
 {
 	if (rc->range < (1 << RC_TOP_BITS)) {
@@ -101,28 +98,49 @@ static ALWAYS_INLINE void rc_normalize(rc_t *rc)
 	}
 }
 
-/* rc_is_bit_1 is called 9 times */
-static speed_inline int rc_is_bit_1(rc_t *rc, uint16_t *p)
+/* rc_is_bit_0 is called 9 times */
+/* Why rc_is_bit_0_helper exists?
+ * Because we want to always expose (rc->code < rc->bound) to optimizer.
+ * Thus rc_is_bit_0 is always inlined, and rc_is_bit_0_helper is inlined
+ * only if we compile for speed.
+ */
+static speed_inline uint32_t rc_is_bit_0_helper(rc_t *rc, uint16_t *p)
 {
 	rc_normalize(rc);
 	rc->bound = *p * (rc->range >> RC_MODEL_TOTAL_BITS);
-	if (rc->code < rc->bound) {
-		rc->range = rc->bound;
-		*p += ((1 << RC_MODEL_TOTAL_BITS) - *p) >> RC_MOVE_BITS;
-		return 0;
-	}
+	return rc->bound;
+}
+static ALWAYS_INLINE int rc_is_bit_0(rc_t *rc, uint16_t *p)
+{
+	uint32_t t = rc_is_bit_0_helper(rc, p);
+	return rc->code < t;
+}
+
+/* Called ~10 times, but very small, thus inlined */
+static speed_inline void rc_update_bit_0(rc_t *rc, uint16_t *p)
+{
+	rc->range = rc->bound;
+	*p += ((1 << RC_MODEL_TOTAL_BITS) - *p) >> RC_MOVE_BITS;
+}
+static speed_inline void rc_update_bit_1(rc_t *rc, uint16_t *p)
+{
 	rc->range -= rc->bound;
 	rc->code -= rc->bound;
 	*p -= *p >> RC_MOVE_BITS;
-	return 1;
 }
 
 /* Called 4 times in unlzma loop */
-static speed_inline int rc_get_bit(rc_t *rc, uint16_t *p, int *symbol)
+static int rc_get_bit(rc_t *rc, uint16_t *p, int *symbol)
 {
-	int ret = rc_is_bit_1(rc, p);
-	*symbol = *symbol * 2 + ret;
-	return ret;
+	if (rc_is_bit_0(rc, p)) {
+		rc_update_bit_0(rc, p);
+		*symbol *= 2;
+		return 0;
+	} else {
+		rc_update_bit_1(rc, p);
+		*symbol = *symbol * 2 + 1;
+		return 1;
+	}
 }
 
 /* Called once */
@@ -248,13 +266,13 @@ unpack_lzma_stream(int src_fd, int dst_fd)
 	header.dst_size = SWAP_LE64(header.dst_size);
 
 	if (header.dict_size == 0)
-		header.dict_size++;
+		header.dict_size = 1;
 
 	buffer = xmalloc(MIN(header.dst_size, header.dict_size));
 
 	num_probs = LZMA_BASE_SIZE + (LZMA_LIT_SIZE << (lc + lp));
 	p = xmalloc(num_probs * sizeof(*p));
-	num_probs += LZMA_LITERAL - LZMA_BASE_SIZE;
+	num_probs = LZMA_LITERAL + (LZMA_LIT_SIZE << (lc + lp));
 	for (i = 0; i < num_probs; i++)
 		p[i] = (1 << RC_MODEL_TOTAL_BITS) >> 1;
 
@@ -264,8 +282,9 @@ unpack_lzma_stream(int src_fd, int dst_fd)
 		int pos_state = (buffer_pos + global_pos) & pos_state_mask;
 
 		prob = p + LZMA_IS_MATCH + (state << LZMA_NUM_POS_BITS_MAX) + pos_state;
-		if (!rc_is_bit_1(rc, prob)) {
+		if (rc_is_bit_0(rc, prob)) {
 			mi = 1;
+			rc_update_bit_0(rc, prob);
 			prob = (p + LZMA_LITERAL
 			        + (LZMA_LIT_SIZE * ((((buffer_pos + global_pos) & literal_pos_mask) << lc)
 			                            + (previous_byte >> (8 - lc))
@@ -321,21 +340,27 @@ unpack_lzma_stream(int src_fd, int dst_fd)
 			int offset;
 			uint16_t *prob_len;
 
+			rc_update_bit_1(rc, prob);
 			prob = p + LZMA_IS_REP + state;
-			if (!rc_is_bit_1(rc, prob)) {
+			if (rc_is_bit_0(rc, prob)) {
+				rc_update_bit_0(rc, prob);
 				rep3 = rep2;
 				rep2 = rep1;
 				rep1 = rep0;
 				state = state < LZMA_NUM_LIT_STATES ? 0 : 3;
 				prob = p + LZMA_LEN_CODER;
 			} else {
-				prob += LZMA_IS_REP_G0 - LZMA_IS_REP;
-				if (!rc_is_bit_1(rc, prob)) {
+				rc_update_bit_1(rc, prob);
+				prob = p + LZMA_IS_REP_G0 + state;
+				if (rc_is_bit_0(rc, prob)) {
+					rc_update_bit_0(rc, prob);
 					prob = (p + LZMA_IS_REP_0_LONG
 					        + (state << LZMA_NUM_POS_BITS_MAX)
 					        + pos_state
 					);
-					if (!rc_is_bit_1(rc, prob)) {
+					if (rc_is_bit_0(rc, prob)) {
+						rc_update_bit_0(rc, prob);
+
 						state = state < LZMA_NUM_LIT_STATES ? 9 : 11;
 #if ENABLE_FEATURE_LZMA_FAST
 						pos = buffer_pos - rep0;
@@ -347,16 +372,25 @@ unpack_lzma_stream(int src_fd, int dst_fd)
 						len = 1;
 						goto string;
 #endif
+					} else {
+						rc_update_bit_1(rc, prob);
 					}
 				} else {
 					uint32_t distance;
 
-					prob += LZMA_IS_REP_G1 - LZMA_IS_REP_G0;
-					distance = rep1;
-					if (rc_is_bit_1(rc, prob)) {
-						prob += LZMA_IS_REP_G2 - LZMA_IS_REP_G1;
-						distance = rep2;
-						if (rc_is_bit_1(rc, prob)) {
+					rc_update_bit_1(rc, prob);
+					prob = p + LZMA_IS_REP_G1 + state;
+					if (rc_is_bit_0(rc, prob)) {
+						rc_update_bit_0(rc, prob);
+						distance = rep1;
+					} else {
+						rc_update_bit_1(rc, prob);
+						prob = p + LZMA_IS_REP_G2 + state;
+						if (rc_is_bit_0(rc, prob)) {
+							rc_update_bit_0(rc, prob);
+							distance = rep2;
+						} else {
+							rc_update_bit_1(rc, prob);
 							distance = rep3;
 							rep3 = rep2;
 						}
@@ -370,20 +404,24 @@ unpack_lzma_stream(int src_fd, int dst_fd)
 			}
 
 			prob_len = prob + LZMA_LEN_CHOICE;
-			if (!rc_is_bit_1(rc, prob_len)) {
-				prob_len += LZMA_LEN_LOW - LZMA_LEN_CHOICE
-				            + (pos_state << LZMA_LEN_NUM_LOW_BITS);
+			if (rc_is_bit_0(rc, prob_len)) {
+				rc_update_bit_0(rc, prob_len);
+				prob_len = (prob + LZMA_LEN_LOW
+				            + (pos_state << LZMA_LEN_NUM_LOW_BITS));
 				offset = 0;
 				num_bits = LZMA_LEN_NUM_LOW_BITS;
 			} else {
-				prob_len += LZMA_LEN_CHOICE_2 - LZMA_LEN_CHOICE;
-				if (!rc_is_bit_1(rc, prob_len)) {
-					prob_len += LZMA_LEN_MID - LZMA_LEN_CHOICE_2
-					            + (pos_state << LZMA_LEN_NUM_MID_BITS);
+				rc_update_bit_1(rc, prob_len);
+				prob_len = prob + LZMA_LEN_CHOICE_2;
+				if (rc_is_bit_0(rc, prob_len)) {
+					rc_update_bit_0(rc, prob_len);
+					prob_len = (prob + LZMA_LEN_MID
+					            + (pos_state << LZMA_LEN_NUM_MID_BITS));
 					offset = 1 << LZMA_LEN_NUM_LOW_BITS;
 					num_bits = LZMA_LEN_NUM_MID_BITS;
 				} else {
-					prob_len += LZMA_LEN_HIGH - LZMA_LEN_CHOICE_2;
+					rc_update_bit_1(rc, prob_len);
+					prob_len = prob + LZMA_LEN_HIGH;
 					offset = ((1 << LZMA_LEN_NUM_LOW_BITS)
 					          + (1 << LZMA_LEN_NUM_MID_BITS));
 					num_bits = LZMA_LEN_NUM_HIGH_BITS;
@@ -400,20 +438,19 @@ unpack_lzma_stream(int src_fd, int dst_fd)
 				       ((len < LZMA_NUM_LEN_TO_POS_STATES ? len :
 				         LZMA_NUM_LEN_TO_POS_STATES - 1)
 				         << LZMA_NUM_POS_SLOT_BITS);
-				rc_bit_tree_decode(rc, prob,
-					LZMA_NUM_POS_SLOT_BITS, &pos_slot);
-				rep0 = pos_slot;
+				rc_bit_tree_decode(rc, prob, LZMA_NUM_POS_SLOT_BITS,
+								   &pos_slot);
 				if (pos_slot >= LZMA_START_POS_MODEL_INDEX) {
 					num_bits = (pos_slot >> 1) - 1;
 					rep0 = 2 | (pos_slot & 1);
-					prob = p + LZMA_ALIGN;
 					if (pos_slot < LZMA_END_POS_MODEL_INDEX) {
 						rep0 <<= num_bits;
-						prob += LZMA_SPEC_POS - LZMA_ALIGN - 1 + rep0 - pos_slot;
+						prob = p + LZMA_SPEC_POS + rep0 - pos_slot - 1;
 					} else {
 						num_bits -= LZMA_NUM_ALIGN_BITS;
 						while (num_bits--)
 							rep0 = (rep0 << 1) | rc_direct_bit(rc);
+						prob = p + LZMA_ALIGN;
 						rep0 <<= LZMA_NUM_ALIGN_BITS;
 						num_bits = LZMA_NUM_ALIGN_BITS;
 					}
@@ -424,7 +461,8 @@ unpack_lzma_stream(int src_fd, int dst_fd)
 							rep0 |= i;
 						i <<= 1;
 					}
-				}
+				} else
+					rep0 = pos_slot;
 				if (++rep0 == 0)
 					break;
 			}