[Mesa-dev] [PATCH 6/9] glcpp: Skip unnecessary line continuations removal

[Thomas Helland]

From: Vladislav Egorov <vegorov180 at gmail.com>

Overwhelming majority of shaders don't use line continuations. In my
shader-db only shaders from the Talos Principle and Serious Sam used
them, less than 1% out of all shaders. Optimize for this case, don't
do any copying if no line continuation was found.
---
 src/compiler/glsl/glcpp/pp.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/compiler/glsl/glcpp/pp.c b/src/compiler/glsl/glcpp/pp.c
index cd86e369b1..50237a87b6 100644
--- a/src/compiler/glsl/glcpp/pp.c
+++ b/src/compiler/glsl/glcpp/pp.c
@@ -117,6 +117,12 @@ remove_line_continuations(glcpp_parser_t *ctx, const char *shader)
 	int collapsed_newlines = 0;
 	int separator_len;
 
+	backslash = strchr(shader, '\\');
+
+	/* No line continuations were found in this shader, our job is done */
+	if (backslash == NULL)
+		return (char *) shader;
+
 	search_start = shader;
 
 	/* Determine what flavor of newlines this shader is using. GLSL
@@ -158,8 +164,6 @@ remove_line_continuations(glcpp_parser_t *ctx, const char *shader)
 	separator_len = strlen(newline_separator);
 
 	while (true) {
-		backslash = strchr(search_start, '\\');
-
 		/* If we have previously collapsed any line-continuations,
 		 * then we want to insert additional newlines at the next
 		 * occurrence of a newline character to avoid changing any
@@ -207,6 +211,8 @@ remove_line_continuations(glcpp_parser_t *ctx, const char *shader)
 			shader = skip_newline (backslash + 1);
 			search_start = shader;
 		}
+
+		backslash = strchr(search_start, '\\');
 	}
 
 	_mesa_string_buffer_append(sb, shader);
-- 
2.13.0