From: Dmitry Stogov <dmitry@zend.com>
Date: Tue, 30 Jul 2013 18:31:37 +0000 (+0400)
Subject: Improved implementation of NOP removal pass from O(n^2) to O(n) (hnw)
X-Git-Tag: php-5.5.2RC1~5
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=cb17c9951182690b75f57cdf1707609a8478af6f;p=php

Improved implementation of NOP removal pass from O(n^2) to O(n) (hnw)
---

diff --git a/ext/opcache/Optimizer/block_pass.c b/ext/opcache/Optimizer/block_pass.c
index b8c381406b..7f874e7a4b 100644
--- a/ext/opcache/Optimizer/block_pass.c
+++ b/ext/opcache/Optimizer/block_pass.c
@@ -558,6 +558,52 @@ static void zend_rebuild_access_path(zend_cfg *cfg, zend_op_array *op_array, int
 		convert_to_string((v)); \
 	}
 
+static void strip_nop(zend_code_block *block)
+{
+	zend_op *opline = block->start_opline;
+	zend_op *end, *new_end;
+	int new_len = 0;
+
+	/* remove leading NOPs */
+	while (block->len > 0 && block->start_opline->opcode == ZEND_NOP) {
+		if (block->len == 1) {
+			/* this block is all NOPs, join with following block */
+			if (block->follow_to) {
+				delete_code_block(block);
+			}
+			return;
+		}
+		block->start_opline++;
+		block->start_opline_no++;
+		block->len--;
+	}
+
+	/* strip the inside NOPs */
+	opline = new_end = block->start_opline;
+	end = opline + block->len;
+
+	while (opline < end) {
+		zend_op *src;
+		int len = 0;
+
+		while (opline < end && opline->opcode == ZEND_NOP) {
+			opline++;
+		}
+		src = opline;
+
+		while (opline < end && opline->opcode != ZEND_NOP) {
+			opline++;
+		}
+		len = opline - src;
+
+		/* move up non-NOP opcodes */
+		memmove(new_end, src, len*sizeof(zend_op));
+
+		new_end += len;
+	}
+	block->len = new_end - block->start_opline;
+}
+
 static void zend_optimize_block(zend_code_block *block, zend_op_array *op_array, char *used_ext TSRMLS_DC)
 {
 	zend_op *opline = block->start_opline;
@@ -1168,45 +1214,7 @@ static void zend_optimize_block(zend_code_block *block, zend_op_array *op_array,
 		opline++;
 	}
 
-	/* remove leading NOPs */
-	while (block->len > 0 && block->start_opline->opcode == ZEND_NOP) {
-		if (block->len == 1) {
-			/* this block is all NOPs, join with following block */
-			if (block->follow_to) {
-				delete_code_block(block);
-			}
-			if (op_array->T) {
-				efree(Tsource);
-			}
-			return;
-		}
-		block->start_opline++;
-		block->start_opline_no++;
-		block->len--;
-	}
-
-	/* strip the inside NOPs */
-	opline = block->start_opline;
-	end = opline + block->len;
-	while (opline < end) {
-		if (opline->opcode == ZEND_NOP) {
-			zend_op *nop = opline + 1;
-			int noplen;
-			while (nop < end && nop->opcode == ZEND_NOP) {
-				nop++;
-			}
-			noplen = nop-opline;
-			if (nop < end) {
-				/* move up non-NOP opcodes */
-				memmove(opline, nop, (end-nop)*sizeof(zend_op));
-			} else {
-				/* all NOPs up to the end, do nothing */
-			}
-			block->len -= noplen;
-			end = block->start_opline + block->len;
-		}
-		opline++;
-	}
+	strip_nop(block);
 
 	if (op_array->T) {
 		efree(Tsource);