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[RFA] More type narrowing in match.pd V2


Here's an updated patch to add more type narrowing to match.pd.

Changes since the last version:

Slight refactoring of the condition by using types_match as suggested by Richi. I also applied the new types_match to 2 other patterns in match.pd where it seemed clearly appropriate.

Additionally the transformation is restricted by using the new single_use predicate. I didn't change other patterns in match.pd to use the new single_use predicate. But some probably could be changed.

This (of course) continues to pass the bootstrap and regression check for x86-linux-gnu.

There's still a ton of work to do in this space. This is meant to be an incremental stand-alone improvement.

OK now?



Jeff
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e006b26..5ee89de 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2015-05-01  Jeff Law  <law@redhat.com>
+
+	* match.pd (bit_and (plus/minus (convert @0) (convert @1) mask): New
+	simplifier to narrow arithmetic.
+
 2015-05-01  Rasmus Villemoes  <rv@rasmusvillemoes.dk>
 
 	* match.pd: New simplification patterns.
diff --git a/gcc/generic-match-head.c b/gcc/generic-match-head.c
index daa56aa..303b237 100644
--- a/gcc/generic-match-head.c
+++ b/gcc/generic-match-head.c
@@ -70,4 +70,20 @@ along with GCC; see the file COPYING3.  If not see
 #include "dumpfile.h"
 #include "generic-match.h"
 
+/* Routine to determine if the types T1 and T2 are effectively
+   the same for GENERIC.  */
 
+inline bool
+types_match (tree t1, tree t2)
+{
+  return TYPE_MAIN_VARIANT (t1) == TYPE_MAIN_VARIANT (t2);
+}
+
+/* Return if T has a single use.  For GENERIC, we assume this is
+   always true.  */
+
+inline bool
+single_use (tree t)
+{
+  return true;
+}
diff --git a/gcc/gimple-match-head.c b/gcc/gimple-match-head.c
index c7b2f95..dc13218 100644
--- a/gcc/gimple-match-head.c
+++ b/gcc/gimple-match-head.c
@@ -861,3 +861,21 @@ do_valueize (tree (*valueize)(tree), tree op)
   return op;
 }
 
+/* Routine to determine if the types T1 and T2 are effectively
+   the same for GIMPLE.  */
+
+inline bool
+types_match (tree t1, tree t2)
+{
+  return types_compatible_p (t1, t2);
+}
+
+/* Return if T has a single use.  For GIMPLE, we also allow any
+   non-SSA_NAME (ie constants) and zero uses to cope with uses
+   that aren't linked up yet.  */
+
+inline bool
+single_use (tree t)
+{
+  return TREE_CODE (t) != SSA_NAME || has_zero_uses (t) || has_single_use (t);
+}
diff --git a/gcc/match.pd b/gcc/match.pd
index 87ecaf1..51a950a 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -289,8 +289,7 @@ along with GCC; see the file COPYING3.  If not see
   (if (((TREE_CODE (@1) == INTEGER_CST
 	 && INTEGRAL_TYPE_P (TREE_TYPE (@0))
 	 && int_fits_type_p (@1, TREE_TYPE (@0)))
-	|| (GIMPLE && types_compatible_p (TREE_TYPE (@0), TREE_TYPE (@1)))
-	|| (GENERIC && TREE_TYPE (@0) == TREE_TYPE (@1)))
+	|| types_match (TREE_TYPE (@0), TREE_TYPE (@1)))
        /* ???  This transform conflicts with fold-const.c doing
 	  Convert (T)(x & c) into (T)x & (T)c, if c is an integer
 	  constants (if x has signed type, the sign bit cannot be set
@@ -949,8 +948,7 @@ along with GCC; see the file COPYING3.  If not see
 /* Unordered tests if either argument is a NaN.  */
 (simplify
  (bit_ior (unordered @0 @0) (unordered @1 @1))
- (if ((GIMPLE && types_compatible_p (TREE_TYPE (@0), TREE_TYPE (@1)))
-      || (GENERIC && TREE_TYPE (@0) == TREE_TYPE (@1)))
+ (if (types_match (TREE_TYPE (@0), TREE_TYPE (@1)))
   (unordered @0 @1)))
 (simplify
  (bit_ior:c (unordered @0 @0) (unordered:c@2 @0 @1))
@@ -1054,7 +1052,7 @@ along with GCC; see the file COPYING3.  If not see
    operation and convert the result to the desired type.  */
 (for op (plus minus)
   (simplify
-    (convert (op (convert@2 @0) (convert@3 @1)))
+    (convert (op@4 (convert@2 @0) (convert@3 @1)))
     (if (INTEGRAL_TYPE_P (type)
 	 /* We check for type compatibility between @0 and @1 below,
 	    so there's no need to check that @1/@3 are integral types.  */
@@ -1070,15 +1068,45 @@ along with GCC; see the file COPYING3.  If not see
 	 && TYPE_PRECISION (type) == GET_MODE_PRECISION (TYPE_MODE (type))
 	 /* The inner conversion must be a widening conversion.  */
 	 && TYPE_PRECISION (TREE_TYPE (@2)) > TYPE_PRECISION (TREE_TYPE (@0))
-	 && ((GENERIC 
-	      && (TYPE_MAIN_VARIANT (TREE_TYPE (@0))
-		  == TYPE_MAIN_VARIANT (TREE_TYPE (@1)))
-	      && (TYPE_MAIN_VARIANT (TREE_TYPE (@0))
-		  == TYPE_MAIN_VARIANT (type)))
-	     || (GIMPLE
-		 && types_compatible_p (TREE_TYPE (@0), TREE_TYPE (@1))
-		 && types_compatible_p (TREE_TYPE (@0), type))))
+	 && types_match (TREE_TYPE (@0), TREE_TYPE (@1))
+	 && types_match (TREE_TYPE (@0), type)
+	 && single_use (@4))
       (if (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0)))
 	(convert (op @0 @1)))
       (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
 	(convert (op (convert:utype @0) (convert:utype @1)))))))
+
+/* This is another case of narrowing, specifically when there's an outer
+   BIT_AND_EXPR which masks off bits outside the type of the innermost
+   operands.   Like the previous case we have to convert the operands
+   to unsigned types to avoid introducing undefined behaviour for the
+   arithmetic operation.  */
+(for op (minus plus)
+  (simplify
+    (bit_and (op@5 (convert@2 @0) (convert@3 @1)) INTEGER_CST@4)
+    (if (INTEGRAL_TYPE_P (type)
+	 /* We check for type compatibility between @0 and @1 below,
+	    so there's no need to check that @1/@3 are integral types.  */
+	 && INTEGRAL_TYPE_P (TREE_TYPE (@0))
+	 && INTEGRAL_TYPE_P (TREE_TYPE (@2))
+	 /* The precision of the type of each operand must match the
+	    precision of the mode of each operand, similarly for the
+	    result.  */
+	 && (TYPE_PRECISION (TREE_TYPE (@0))
+	     == GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (@0))))
+	 && (TYPE_PRECISION (TREE_TYPE (@1))
+	     == GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (@1))))
+	 && TYPE_PRECISION (type) == GET_MODE_PRECISION (TYPE_MODE (type))
+	 /* The inner conversion must be a widening conversion.  */
+	 && TYPE_PRECISION (TREE_TYPE (@2)) > TYPE_PRECISION (TREE_TYPE (@0))
+	 && types_match (TREE_TYPE (@0), TREE_TYPE (@1))
+	 && (tree_int_cst_min_precision (@4, UNSIGNED)
+	     <= TYPE_PRECISION (TREE_TYPE (@0)))
+	 && single_use (@5))
+      (if (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0)))
+	(with { tree ntype = TREE_TYPE (@0); }
+	  (convert (bit_and (op @0 @1) (convert:ntype @4)))))
+      (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
+	(convert (bit_and (op (convert:utype @0) (convert:utype @1))
+			  (convert:utype @4)))))))
+
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 2aedc46..bd32179 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2015-05-01  Jeff Law  <law@redhat.com>
+
+	* gcc.dg/tree-ssa/shorten-1.c: New test.
+
 2015-05-01  Rasmus Villemoes  <rv@rasmusvillemoes.dk>
 
 	* gcc.dg/20150120-1.c: New test.
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/shorten-1.c b/gcc/testsuite/gcc.dg/tree-ssa/shorten-1.c
new file mode 100644
index 0000000..cecdd44
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/shorten-1.c
@@ -0,0 +1,78 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+extern const unsigned char mode_ibit[];
+extern const unsigned char mode_fbit[];
+extern const signed char smode_ibit[];
+extern const signed char smode_fbit[];
+
+/* We use bit-and rather than modulo to ensure we're actually
+   testing the desired match.pd pattern.  */
+unsigned char
+muufubar (int indx)
+{
+  int ret = (mode_fbit [indx] - mode_ibit [indx]) & 3;
+  return ret;
+}
+
+signed char
+msufubar (int indx)
+{
+  int ret = (mode_fbit [indx] - mode_ibit [indx]) & 3;
+  return ret;
+}
+
+unsigned char
+musfubar (int indx)
+{
+  int ret = (smode_fbit [indx] - smode_ibit [indx]) & 3;
+  return ret;
+}
+
+signed char
+mssfubar (int indx)
+{
+  int ret = (smode_fbit [indx] - smode_ibit [indx]) & 3;
+  return ret;
+}
+
+
+unsigned char
+puufubar (int indx)
+{
+  int ret = (mode_fbit [indx] + mode_ibit [indx]) & 3;
+  return ret;
+}
+
+signed char
+psufubar (int indx)
+{
+  int ret = (mode_fbit [indx] + mode_ibit [indx]) & 3;
+  return ret;
+}
+
+unsigned char
+pusfubar (int indx)
+{
+  int ret = (smode_fbit [indx] + smode_ibit [indx]) & 3;
+  return ret;
+}
+
+signed char
+pssfubar (int indx)
+{
+  int ret = (smode_fbit [indx] + smode_ibit [indx]) & 3;
+  return ret;
+}
+
+/* The shortening patterns in match.pd should arrange to do the
+   arithmetic in char modes and thus any casts to ints should
+   have been removed.  */
+/* { dg-final {scan-tree-dump-not "\\(int\\)" "optimized"} } */
+
+/* We should have casted 4 operands from signed to unsigned char types.  */
+/* { dg-final {scan-tree-dump-times "\\(unsigned char\\)" 8 "optimized" } } */
+
+/* And two return values should have been casted from unsigned char to
+   a normal char.  */
+/* { dg-final {scan-tree-dump-times "\\(signed char\\)" 4 "optimized" } } */

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