Mesa (master): glcpp: Skip unnecessary line continuations removal

[Timothy Arceri]

Module: Mesa
Branch: master
Commit: 4a47247523e678a3a9d3939e8a3c217188b99452
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=4a47247523e678a3a9d3939e8a3c217188b99452

Author: Vladislav Egorov <vegorov180 at gmail.com>
Date:   Sun May 21 22:49:17 2017 +0200

glcpp: Skip unnecessary line continuations removal

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.

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>

---

 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 c526f37719..96125f2e2f 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)
         char newline_separator[3];
 	int collapsed_newlines = 0;
 
+	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
@@ -157,8 +163,6 @@ remove_line_continuations(glcpp_parser_t *ctx, const char *shader)
 	}
 
 	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
@@ -204,6 +208,8 @@ remove_line_continuations(glcpp_parser_t *ctx, const char *shader)
 			shader = skip_newline (backslash + 1);
 			search_start = shader;
 		}
+
+		backslash = strchr(search_start, '\\');
 	}
 
 	ralloc_strcat(&clean, shader);