[multiple changes]

2014-11-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    PR tree-optimization/63761
    * tree-ssa-math-opts.c (bswap_replace): Construct gsi from cur_stmt
    rather than taking it as a parameter. Add some comments to explain the
    gsi_move_before in case of load and why canonicalization of bswap into
    a rotation is only done for 16bit values.
    (pass_optimize_bswap::execute): Adapt for loop via gsi to make gsi
    refer to the statement just before cur_stmt. Ignore 16bit bswap that
    are already in canonical form. Adapt bswap_replace to removal of its
    gsi parameter.

    2014-11-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/testsuite/
    PR tree-optimization/63761
    * gcc.c-torture/compile/pr63761.c: New test.

From-SVN: r217409

gcc/ChangeLog

@@ -1,3 +1,15 @@
+2014-11-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	PR tree-optimization/63761
+	* tree-ssa-math-opts.c (bswap_replace): Construct gsi from cur_stmt
+	rather than taking it as a parameter. Add some comments to explain the
+	gsi_move_before in case of load and why canonicalization of bswap into
+	a rotation is only done for 16bit values.
+	(pass_optimize_bswap::execute): Adapt for loop via gsi to make gsi
+	refer to the statement just before cur_stmt. Ignore 16bit bswap that
+	are already in canonical form. Adapt bswap_replace to removal of its
+	gsi parameter.
+
 2014-11-12  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* rtl.h (rtx_function, for_each_rtx, for_each_rtx_in_insn): Delete.

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2014-11-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	PR tree-optimization/63761
+	* gcc.c-torture/compile/pr63761.c: New test.
+
 2014-11-12  Jiong Wang  <jiong.wang@arm.com>
 
 	* lib/gcc-dg.exp (${tool}_load): Truncate gcc output.

gcc/testsuite/gcc.c-torture/compile/pr63761.c

@@ -0,0 +1,17 @@
+int a, b;
+short c;
+
+void fn1 ();
+
+void
+fn2 (unsigned short p1)
+{
+  int d;
+
+  c = p1 >> 8 | p1 << 8;
+  d = b;
+  if (d)
+    fn1 ();
+  a = d >> 8 & 0x00FF
+    | d << 8 & 0xFF00;
+}

gcc/tree-ssa-math-opts.c

@@ -2172,23 +2172,28 @@ public:
 
 }; // class pass_optimize_bswap
 
-/* Perform the bswap optimization: replace the statement CUR_STMT at
+/* Perform the bswap optimization: replace the expression computed in the rhs
-   GSI with a load of type, VUSE and set-alias as described by N if a
+   of CUR_STMT by an equivalent bswap, load or load + bswap expression.
-   memory source is involved (N->base_addr is non null), followed by
+   Which of these alternatives replace the rhs is given by N->base_addr (non
-   the builtin bswap invocation in FNDECL if BSWAP is true.  SRC_STMT
+   null if a load is needed) and BSWAP.  The type, VUSE and set-alias of the
-   gives where should the replacement be made.  It also gives the
+   load to perform are also given in N while the builtin bswap invoke is given
-   source on which CUR_STMT is operating via its rhs's first tree nad
+   in FNDEL.  Finally, if a load is involved, SRC_STMT refers to one of the
-   N->range gives the size of the expression involved for maintaining
+   load statements involved to construct the rhs in CUR_STMT and N->range gives
-   some statistics.  */
+   the size of the rhs expression for maintaining some statistics.
+
+   Note that if the replacement involve a load, CUR_STMT is moved just after
+   SRC_STMT to do the load with the same VUSE which can lead to CUR_STMT
+   changing of basic block.  */
 
 static bool
-bswap_replace (gimple cur_stmt, gimple_stmt_iterator gsi, gimple src_stmt,
+bswap_replace (gimple cur_stmt, gimple src_stmt, tree fndecl, tree bswap_type,
-	       tree fndecl, tree bswap_type, tree load_type,
+	       tree load_type, struct symbolic_number *n, bool bswap)
-	       struct symbolic_number *n, bool bswap)
 {
+  gimple_stmt_iterator gsi;
   tree src, tmp, tgt;
   gimple bswap_stmt;
 
+  gsi = gsi_for_stmt (cur_stmt);
   src = gimple_assign_rhs1 (src_stmt);
   tgt = gimple_assign_lhs (cur_stmt);
 
@@ -2207,6 +2212,9 @@ bswap_replace (gimple cur_stmt, gimple_stmt_iterator gsi, gimple src_stmt,
 	  && SLOW_UNALIGNED_ACCESS (TYPE_MODE (load_type), align))
 	return false;
 
+      /* Move cur_stmt just before  one of the load of the original
+	 to ensure it has the same VUSE.  See PR61517 for what could
+	 go wrong.  */
       gsi_move_before (&gsi, &gsi_ins);
       gsi = gsi_for_stmt (cur_stmt);
 
@@ -2293,7 +2301,10 @@ bswap_replace (gimple cur_stmt, gimple_stmt_iterator gsi, gimple src_stmt,
 
   tmp = src;
 
-  /* Canonical form for 16 bit bswap is a rotate expression.  */
+  /* Canonical form for 16 bit bswap is a rotate expression.  Only 16bit values
+     are considered as rotation of 2N bit values by N bits is generally not
+     equivalent to a bswap.  Consider for instance 0x01020304 >> 16 which gives
+     0x03040102 while a bswap for that value is 0x04030201.  */
   if (bswap && n->range == 16)
     {
       tree count = build_int_cst (NULL, BITS_PER_UNIT);
@@ -2393,10 +2404,10 @@ pass_optimize_bswap::execute (function *fun)
       gimple_stmt_iterator gsi;
 
       /* We do a reverse scan for bswap patterns to make sure we get the
-	 widest match. As bswap pattern matching doesn't handle
+	 widest match. As bswap pattern matching doesn't handle previously
-	 previously inserted smaller bswap replacements as sub-
+	 inserted smaller bswap replacements as sub-patterns, the wider
-	 patterns, the wider variant wouldn't be detected.  */
+	 variant wouldn't be detected.  */
-      for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
+      for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
         {
 	  gimple src_stmt, cur_stmt = gsi_stmt (gsi);
 	  tree fndecl = NULL_TREE, bswap_type = NULL_TREE, load_type;
@@ -2404,6 +2415,14 @@ pass_optimize_bswap::execute (function *fun)
 	  struct symbolic_number n;
 	  bool bswap;
 
+	  /* This gsi_prev (&gsi) is not part of the for loop because cur_stmt
+	     might be moved to a different basic block by bswap_replace and gsi
+	     must not points to it if that's the case.  Moving the gsi_prev
+	     there make sure that gsi points to the statement previous to
+	     cur_stmt while still making sure that all statements are
+	     considered in this basic block.  */
+	  gsi_prev (&gsi);
+
 	  if (!is_gimple_assign (cur_stmt))
 	    continue;
 
@@ -2431,6 +2450,9 @@ pass_optimize_bswap::execute (function *fun)
 	  switch (n.range)
 	    {
 	    case 16:
+	      /* Already in canonical form, nothing to do.  */
+	      if (code == LROTATE_EXPR || code == RROTATE_EXPR)
+		continue;
 	      load_type = uint16_type_node;
 	      if (bswap16_p)
 		{
@@ -2461,8 +2483,8 @@ pass_optimize_bswap::execute (function *fun)
 	  if (bswap && !fndecl)
 	    continue;
 
-	  if (bswap_replace (cur_stmt, gsi, src_stmt, fndecl, bswap_type,
+	  if (bswap_replace (cur_stmt, src_stmt, fndecl, bswap_type, load_type,
-			     load_type, &n, bswap))
+			     &n, bswap))
 	    changed = true;
 	}
     }