Re: Remove redundant AND from count reduction loop

[Marc Glisse]

On Tue, 23 Jun 2015, Richard Sandiford wrote:

+/* Vector comparisons are defined to produce all-one or all-zero results.  */
+(simplify
+ (vec_cond @0 integer_all_onesp@1 integer_zerop@2)
+ (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))
+   (convert @0)))

I am trying to understand why the test tree_nop_conversion_p is the right 
one (at least for the transformations not using VIEW_CONVERT_EXPR). By 
definition of VEC_COND_EXPR, type and TREE_TYPE (@0) are both integer 
vector types of the same size and number of elements. It thus seems like a 
conversion is always fine. For vectors, tree_nop_conversion_p apparently 
only checks that they have the same mode (quite often VOIDmode I guess).

+/* We could instead convert all instances of the vec_cond to negate,
+   but that isn't necessarily a win on its own.  */
+(simplify
+ (plus:c @3 (vec_cond @0 integer_each_onep@1 integer_zerop@2))
+ (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))
+  (minus @3 (convert @0))))
+
+(simplify
+ (plus:c @3 (view_convert_expr

Aren't we suppose to drop _expr in match.pd?

+            (vec_cond @0 integer_each_onep@1 integer_zerop@2)))
+ (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))
+  (minus @3 (convert @0))))
+
+(simplify
+ (minus @3 (vec_cond @0 integer_each_onep@1 integer_zerop@2))
+ (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))
+  (plus @3 (convert @0))))
+
+(simplify
+ (minus @3 (view_convert_expr
+           (vec_cond @0 integer_each_onep@1 integer_zerop@2)))
+ (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))
+  (plus @3 (convert @0))))
+
/* Simplifications of comparisons.  */

/* We can simplify a logical negation of a comparison to the
Index: gcc/testsuite/gcc.target/aarch64/vect-add-sub-cond.c
===================================================================
--- /dev/null   2015-06-02 17:27:28.541944012 +0100
+++ gcc/testsuite/gcc.target/aarch64/vect-add-sub-cond.c        2015-06-23 
12:06:27.120203685 +0100
@@ -0,0 +1,94 @@
+/* Make sure that vector comaprison results are not unnecessarily ANDed
+   with vectors of 1.  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-vectorize" } */
+
+#define COUNT1(X) if (X) count += 1
+#define COUNT2(X) if (X) count -= 1
+#define COUNT3(X) count += (X)
+#define COUNT4(X) count -= (X)
+
+#define COND1(X) (X)
+#define COND2(X) ((X) ? 1 : 0)
+#define COND3(X) ((X) ? -1 : 0)
+#define COND4(X) ((X) ? 0 : 1)
+#define COND5(X) ((X) ? 0 : -1)
+
+#define TEST_LT(X, Y) ((X) < (Y))
+#define TEST_LE(X, Y) ((X) <= (Y))
+#define TEST_GT(X, Y) ((X) > (Y))
+#define TEST_GE(X, Y) ((X) >= (Y))
+#define TEST_EQ(X, Y) ((X) == (Y))
+#define TEST_NE(X, Y) ((X) != (Y))
+
+#define COUNT_LOOP(ID, TYPE, CMP_ARRAY, TEST, COUNT) \
+  TYPE \
+  reduc_##ID (__typeof__ (CMP_ARRAY[0]) x) \
+  { \
+    TYPE count = 0; \
+    for (unsigned int i = 0; i < 1024; ++i) \
+      COUNT (TEST (CMP_ARRAY[i], x)); \
+    return count; \
+  }
+
+#define COND_LOOP(ID, ARRAY, CMP_ARRAY, TEST, COND) \
+  void \
+  plus_##ID (__typeof__ (CMP_ARRAY[0]) x) \
+  { \
+    for (unsigned int i = 0; i < 1024; ++i) \
+      ARRAY[i] += COND (TEST (CMP_ARRAY[i], x)); \
+  } \
+  void \
+  plusc_##ID (void) \
+  { \
+    for (unsigned int i = 0; i < 1024; ++i) \
+      ARRAY[i] += COND (TEST (CMP_ARRAY[i], 10)); \
+  } \
+  void \
+  minus_##ID (__typeof__ (CMP_ARRAY[0]) x) \
+  { \
+    for (unsigned int i = 0; i < 1024; ++i) \
+      ARRAY[i] -= COND (TEST (CMP_ARRAY[i], x)); \
+  } \
+  void \
+  minusc_##ID (void) \
+  { \
+    for (unsigned int i = 0; i < 1024; ++i) \
+      ARRAY[i] += COND (TEST (CMP_ARRAY[i], 1)); \
+  }
+
+#define ALL_LOOPS(ID, ARRAY, CMP_ARRAY, TEST) \
+  typedef __typeof__(ARRAY[0]) ID##_type; \
+  COUNT_LOOP (ID##_1, ID##_type, CMP_ARRAY, TEST, COUNT1) \
+  COUNT_LOOP (ID##_2, ID##_type, CMP_ARRAY, TEST, COUNT2) \
+  COUNT_LOOP (ID##_3, ID##_type, CMP_ARRAY, TEST, COUNT3) \
+  COUNT_LOOP (ID##_4, ID##_type, CMP_ARRAY, TEST, COUNT4) \
+  COND_LOOP (ID##_1, ARRAY, CMP_ARRAY, TEST, COND1) \
+  COND_LOOP (ID##_2, ARRAY, CMP_ARRAY, TEST, COND2) \
+  COND_LOOP (ID##_3, ARRAY, CMP_ARRAY, TEST, COND3) \
+  COND_LOOP (ID##_4, ARRAY, CMP_ARRAY, TEST, COND4) \
+  COND_LOOP (ID##_5, ARRAY, CMP_ARRAY, TEST, COND5)
+
+signed int asi[1024] __attribute__ ((aligned (16)));
+unsigned int aui[1024] __attribute__ ((aligned (16)));
+signed long long asl[1024] __attribute__ ((aligned (16)));
+unsigned long long aul[1024] __attribute__ ((aligned (16)));
+float af[1024] __attribute__ ((aligned (16)));
+double ad[1024] __attribute__ ((aligned (16)));
+
+ALL_LOOPS (si_si, aui, asi, TEST_LT)
+ALL_LOOPS (ui_si, aui, asi, TEST_LE)
+ALL_LOOPS (si_ui, aui, asi, TEST_GT)
+ALL_LOOPS (ui_ui, aui, asi, TEST_GE)
+ALL_LOOPS (sl_sl, asl, asl, TEST_NE)
+ALL_LOOPS (ul_ul, aul, aul, TEST_NE)
+ALL_LOOPS (si_f, asi, af, TEST_LE)
+ALL_LOOPS (ui_f, aui, af, TEST_GT)
+ALL_LOOPS (sl_d, asl, ad, TEST_GE)
+ALL_LOOPS (ul_d, aul, ad, TEST_GT)
+
+/* { dg-final { scan-assembler-not "\tand\t" } } */
+/* { dg-final { scan-assembler-not "\tld\[^\t\]*\t\[wx\]" } } */
+/* { dg-final { scan-assembler-not "\tst\[^\t\]*\t\[wx\]" } } */
+/* { dg-final { scan-assembler "\tldr\tq" } } */
+/* { dg-final { scan-assembler "\tstr\tq" } } */

--
Marc Glisse