[Mesa-dev] [PATCH] glcpp: Avoid unnecessary call to strlen

[Thomas Helland]

Length of the token was already calculated by flex and stored in yyleng,
no need to implicitly call strlen() via linear_strdup().

Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>
Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>

V2: Also convert this pattern in glsl_lexer.ll

V3: Remove a misplaced comment

V4: Use a temporary char to avoid type change
    Remove bogus +1 on length check of identifier
---
 src/compiler/glsl/glcpp/glcpp-lex.l |  9 ++++++++-
 src/compiler/glsl/glsl_lexer.ll     | 39 +++++++++++++++++++++++++++++--------
 2 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/src/compiler/glsl/glcpp/glcpp-lex.l b/src/compiler/glsl/glcpp/glcpp-lex.l
index 381b97364a..9cfcc12022 100644
--- a/src/compiler/glsl/glcpp/glcpp-lex.l
+++ b/src/compiler/glsl/glcpp/glcpp-lex.l
@@ -101,7 +101,14 @@ void glcpp_set_column (int  column_no , yyscan_t yyscanner);
 #define RETURN_STRING_TOKEN(token)					\
 	do {								\
 		if (! parser->skipping) {				\
-			yylval->str = linear_strdup(yyextra->linalloc, yytext);	\
+			/* We're not doing linear_strdup here, to avoid \
+			 * an implicit call on strlen() for the length  \
+			 * of the string, as this is already found by   \
+			 * flex and stored in yyleng */                 \
+			void *mem_ctx = yyextra->linalloc;		\
+			yylval->str = linear_alloc_child(mem_ctx,	\
+							 yyleng + 1);	\
+			memcpy(yylval->str, yytext, yyleng + 1);        \
 			RETURN_TOKEN_NEVER_SKIP (token);		\
 		}							\
 	} while(0)
diff --git a/src/compiler/glsl/glsl_lexer.ll b/src/compiler/glsl/glsl_lexer.ll
index 7c41455d98..56519bf92d 100644
--- a/src/compiler/glsl/glsl_lexer.ll
+++ b/src/compiler/glsl/glsl_lexer.ll
@@ -81,8 +81,13 @@ static int classify_identifier(struct _mesa_glsl_parse_state *, const char *);
 			  "illegal use of reserved word `%s'", yytext);	\
 	 return ERROR_TOK;						\
       } else {								\
-	 void *mem_ctx = yyextra->linalloc;					\
-	 yylval->identifier = linear_strdup(mem_ctx, yytext);		\
+	 /* We're not doing linear_strdup here, to avoid an implicit    \
+	  * call on strlen() for the length of the string, as this is   \
+	  * already found by flex and stored in yyleng */               \
+	 void *mem_ctx = yyextra->linalloc;				\
+         char *id = (char *) linear_alloc_child(mem_ctx, yyleng + 1);   \
+         memcpy(id, yytext, yyleng + 1);                                \
+         yylval->identifier = id;                                       \
 	 return classify_identifier(yyextra, yytext);			\
       }									\
    } while (0)
@@ -261,8 +266,14 @@ HASH		^{SPC}#{SPC}
 <PP>[ \t\r]*			{ }
 <PP>:				return COLON;
 <PP>[_a-zA-Z][_a-zA-Z0-9]*	{
-				   void *mem_ctx = yyextra->linalloc;
-				   yylval->identifier = linear_strdup(mem_ctx, yytext);
+				   /* We're not doing linear_strdup here, to avoid an implicit call
+				    * on strlen() for the length of the string, as this is already
+				    * found by flex and stored in yyleng
+				    */
+                                    void *mem_ctx = yyextra->linalloc;
+                                    char *id = (char *) linear_alloc_child(mem_ctx, yyleng + 1);
+                                    memcpy(id, yytext, yyleng + 1);
+                                    yylval->identifier = id;
 				   return IDENTIFIER;
 				}
 <PP>[1-9][0-9]*			{
@@ -449,8 +460,14 @@ layout		{
                       || yyextra->ARB_tessellation_shader_enable) {
 		      return LAYOUT_TOK;
 		   } else {
-		      void *mem_ctx = yyextra->linalloc;
-		      yylval->identifier = linear_strdup(mem_ctx, yytext);
+		      /* We're not doing linear_strdup here, to avoid an implicit call
+		       * on strlen() for the length of the string, as this is already
+		       * found by flex and stored in yyleng
+		       */
+                      void *mem_ctx = yyextra->linalloc;
+                      char *id = (char *) linear_alloc_child(mem_ctx, yyleng + 1);
+                      memcpy(id, yytext, yyleng + 1);
+                      yylval->identifier = id;
 		      return classify_identifier(yyextra, yytext);
 		   }
 		}
@@ -621,12 +638,18 @@ u64vec4		KEYWORD_WITH_ALT(0, 0, 0, 0, yyextra->ARB_gpu_shader_int64_enable, U64V
 [_a-zA-Z][_a-zA-Z0-9]*	{
 			    struct _mesa_glsl_parse_state *state = yyextra;
 			    void *ctx = state->linalloc;
-			    if (state->es_shader && strlen(yytext) > 1024) {
+			    if (state->es_shader && yyleng > 1024) {
 			       _mesa_glsl_error(yylloc, state,
 			                        "Identifier `%s' exceeds 1024 characters",
 			                        yytext);
 			    } else {
-			      yylval->identifier = linear_strdup(ctx, yytext);
+			      /* We're not doing linear_strdup here, to avoid an implicit call
+			       * on strlen() for the length of the string, as this is already
+			       * found by flex and stored in yyleng
+			       */
+                              char *id = (char *) linear_alloc_child(ctx, yyleng + 1);
+                              memcpy(id, yytext, yyleng + 1);
+                              yylval->identifier = id;
 			    }
 			    return classify_identifier(state, yytext);
 			}
-- 
2.13.3