From 0f3d210f05194fed979e83c3a134fccb9f3505cd Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <icculus@icculus.org>
Date: Wed, 17 Apr 2013 23:30:10 -0400
Subject: [PATCH] Optimizations to preprocessor's find_define().

- don't check for __FILE__ and __LINE__ until after we've checked our hash,
  since this is the less likely case.
- Check against the hard-coded hash value of the strings "__FILE__" and
  "__LINE__" to avoid unnecessary strcmp() calls.

This dropped the profile of this function from 20% of our total CPU time to
 10%. Of that 10%, 70% is now the hashing function.
---
 mojoshader_preprocessor.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/mojoshader_preprocessor.c b/mojoshader_preprocessor.c
index 5137bd4a..916243ae 100644
--- a/mojoshader_preprocessor.c
+++ b/mojoshader_preprocessor.c
@@ -437,7 +437,22 @@ static int remove_define(Context *ctx, const char *sym)
 
 static const Define *find_define(Context *ctx, const char *sym)
 {
-    if ( (ctx->file_macro) && (strcmp(sym, "__FILE__") == 0) )
+    const uint8 hash = hash_define(sym);
+    Define *bucket = ctx->define_hashtable[hash];
+    while (bucket)
+    {
+        if (strcmp(bucket->identifier, sym) == 0)
+            return bucket;
+        bucket = bucket->next;
+    } // while
+
+    const uint8 filestrhash = 67;
+    assert(hash_define("__FILE__") == filestrhash);
+
+    const uint8 linestrhash = 75;
+    assert(hash_define("__LINE__") == linestrhash);
+
+    if ( (hash == filestrhash) && (ctx->file_macro) && (strcmp(sym, "__FILE__") == 0) )
     {
         Free(ctx, (char *) ctx->file_macro->definition);
         const IncludeState *state = ctx->include_stack;
@@ -453,7 +468,7 @@ static const Define *find_define(Context *ctx, const char *sym)
         return ctx->file_macro;
     } // if
 
-    else if ( (ctx->line_macro) && (strcmp(sym, "__LINE__") == 0) )
+    else if ( (hash == linestrhash) && (ctx->line_macro) && (strcmp(sym, "__LINE__") == 0) )
     {
         Free(ctx, (char *) ctx->line_macro->definition);
         const IncludeState *state = ctx->include_stack;
@@ -468,14 +483,6 @@ static const Define *find_define(Context *ctx, const char *sym)
         return ctx->line_macro;
     } // else
 
-    const uint8 hash = hash_define(sym);
-    Define *bucket = ctx->define_hashtable[hash];
-    while (bucket)
-    {
-        if (strcmp(bucket->identifier, sym) == 0)
-            return bucket;
-        bucket = bucket->next;
-    } // while
     return NULL;
 } // find_define