From: drh <drh@noemail.net>
Date: Thu, 2 Jan 2014 17:57:16 +0000 (+0000)
Subject: Be more aggressive in optimizing constant conditional expressions.
X-Git-Tag: version-3.8.3~68
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=991a19851112ffb03946a003350e9e148d631348;p=thirdparty%2Fsqlite.git

Be more aggressive in optimizing constant conditional expressions.

FossilOrigin-Name: b7e39851a75b87ebca747b26a39989560fd6362b
---

diff --git a/manifest b/manifest
index e254e7cba0..142a875f5d 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Try\sto\sdetect\sprocess\sID\schanges\sdue\sto\sfork()\scalls\sin\sos_unix.c\sand\nreset\sthe\sPRNG\swhen\sa\sprocess\sID\schange\sis\sdetected.
-D 2014-01-01T15:18:36.453
+C Be\smore\saggressive\sin\soptimizing\sconstant\sconditional\sexpressions.
+D 2014-01-02T17:57:16.874
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 2ef13430cd359f7b361bb863504e227b25cc7f81
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -175,7 +175,7 @@ F src/complete.c dc1d136c0feee03c2f7550bafc0d29075e36deac
 F src/ctime.c 77779efbe78dd678d84bfb4fc2e87b6b6ad8dccd
 F src/date.c 593c744b2623971e45affd0bde347631bdfa4625
 F src/delete.c 821da82527c24496bef0677ed4f61a53b44c27ee
-F src/expr.c ffe4bc79c66f711f450a6113fbd1943b9b2380f7
+F src/expr.c ca0959386f01d6e5d4dc67b362a4e4c912ebd054
 F src/fault.c 160a0c015b6c2629d3899ed2daf63d75754a32bb
 F src/fkey.c 2ab0f5384b70594468ef3ac5c7ed8ca24bfd17d5
 F src/func.c 6325ac2ec10833ccf4d5c36d323709221d37ea19
@@ -1147,7 +1147,7 @@ F tool/vdbe-compress.tcl 0cf56e9263a152b84da86e75a5c0cdcdb7a47891
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
 F tool/win/sqlite.vsix 030f3eeaf2cb811a3692ab9c14d021a75ce41fff
-P a221aa82bb5496885fd0bf76e4601443799511de
-R 0b5cbfb8643918ccfe030368af8a9f9c
+P e1eba1fb09d7db49d77928bd115b27b8002ae640
+R 8c33ee4ecd82143d9dd9bc5270372c1d
 U drh
-Z 8d0b25dd26eff92b0e8709464c57dd81
+Z 948115126ed1b38f36b2ba1121c24109
diff --git a/manifest.uuid b/manifest.uuid
index 002b2fbf68..38faece72d 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-e1eba1fb09d7db49d77928bd115b27b8002ae640
\ No newline at end of file
+b7e39851a75b87ebca747b26a39989560fd6362b
\ No newline at end of file
diff --git a/src/expr.c b/src/expr.c
index 8ee73acb78..0db51fe43f 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -523,16 +523,25 @@ Expr *sqlite3PExpr(
 }
 
 /*
-** Return 1 if an expression must be FALSE in all cases and 0 if the
-** expression might be true.  This is an optimization.  If is OK to
-** return 0 here even if the expression really is always false (a 
-** false negative).  But it is a bug to return 1 if the expression
-** might be true in some rare circumstances (a false positive.)
+** If the expression is always either TRUE or FALSE (respectively),
+** then return 1.  If one cannot determine the truth value of the
+** expression at compile-time return 0.
+**
+** This is an optimization.  If is OK to return 0 here even if
+** the expression really is always false or false (a false negative).
+** But it is a bug to return 1 if the expression might have different
+** boolean values in different circumstances (a false positive.)
 **
 ** Note that if the expression is part of conditional for a
 ** LEFT JOIN, then we cannot determine at compile-time whether or not
 ** is it true or false, so always return 0.
 */
+static int exprAlwaysTrue(Expr *p){
+  int v = 0;
+  if( ExprHasProperty(p, EP_FromJoin) ) return 0;
+  if( !sqlite3ExprIsInteger(p, &v) ) return 0;
+  return v!=0;
+}
 static int exprAlwaysFalse(Expr *p){
   int v = 0;
   if( ExprHasProperty(p, EP_FromJoin) ) return 0;
@@ -3614,10 +3623,16 @@ void sqlite3ExprIfTrue(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
     }
 #endif
     default: {
-      r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
-      sqlite3VdbeAddOp3(v, OP_If, r1, dest, jumpIfNull!=0);
-      testcase( regFree1==0 );
-      testcase( jumpIfNull==0 );
+      if( exprAlwaysTrue(pExpr) ){
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, dest);
+      }else if( exprAlwaysFalse(pExpr) ){
+        /* No-op */
+      }else{
+        r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
+        sqlite3VdbeAddOp3(v, OP_If, r1, dest, jumpIfNull!=0);
+        testcase( regFree1==0 );
+        testcase( jumpIfNull==0 );
+      }
       break;
     }
   }
@@ -3759,10 +3774,16 @@ void sqlite3ExprIfFalse(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
     }
 #endif
     default: {
-      r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
-      sqlite3VdbeAddOp3(v, OP_IfNot, r1, dest, jumpIfNull!=0);
-      testcase( regFree1==0 );
-      testcase( jumpIfNull==0 );
+      if( exprAlwaysFalse(pExpr) ){
+        sqlite3VdbeAddOp2(v, OP_Goto, 0, dest);
+      }else if( exprAlwaysTrue(pExpr) ){
+        /* no-op */
+      }else{
+        r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
+        sqlite3VdbeAddOp3(v, OP_IfNot, r1, dest, jumpIfNull!=0);
+        testcase( regFree1==0 );
+        testcase( jumpIfNull==0 );
+      }
       break;
     }
   }