[PATCH] tree-optimization/99856 - fix overwideing pattern creation

[Richard Biener]

This fixes an omission of promoting a bit-precision required precision
to a vector element precision.

Bootstrapped & tested on x86_64-unknown-linux-gnu, pushed.

2021-04-01  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/99856
        * tree-vect-patterns.c (vect_recog_over_widening_pattern): Promote
        precision to vector element precision.

        * gcc.dg/vect/pr99856.c: New testcase.
---
 gcc/testsuite/gcc.dg/vect/pr99856.c | 33 +++++++++++++++++++++++++++++
 gcc/tree-vect-patterns.c            |  1 +
 2 files changed, 34 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/vect/pr99856.c

diff --git a/gcc/testsuite/gcc.dg/vect/pr99856.c 
b/gcc/testsuite/gcc.dg/vect/pr99856.c
new file mode 100644
index 00000000000..e5d2a45be57
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr99856.c
@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target vect_int } */
+/* { dg-require-effective-target vect_unpack } */
+/* { dg-require-effective-target vect_pack_trunc } */
+
+#define SHIFTFORDIV255(a)\
+    ((((a) >> 8) + a) >> 8)
+
+#define DIV255(a)\
+    SHIFTFORDIV255(a + 0x80)
+
+typedef unsigned char uint8_t;
+
+void
+opSourceOver_premul(uint8_t* restrict Rrgba,
+                    const uint8_t* restrict Srgba,
+                    const uint8_t* restrict Drgba, int len)
+{
+  Rrgba = __builtin_assume_aligned (Rrgba, __BIGGEST_ALIGNMENT__);
+  Srgba = __builtin_assume_aligned (Rrgba, __BIGGEST_ALIGNMENT__);
+  Drgba = __builtin_assume_aligned (Rrgba, __BIGGEST_ALIGNMENT__);
+  int i = 0;
+  for (; i < len*4; i += 4)
+    {
+      uint8_t Sa = Srgba[i + 3];
+      Rrgba[i + 0] = DIV255(Srgba[i + 0] * 255 + Drgba[i + 0] * (255 - Sa));
+      Rrgba[i + 1] = DIV255(Srgba[i + 1] * 255 + Drgba[i + 1] * (255 - Sa));
+      Rrgba[i + 2] = DIV255(Srgba[i + 2] * 255 + Drgba[i + 2] * (255 - Sa));
+      Rrgba[i + 3] = DIV255(Srgba[i + 3] * 255 + Drgba[i + 3] * (255 - Sa));
+    }
+}
+
+/* { dg-final { scan-tree-dump "vectorized 1 loops in function" "vect" } } */
diff --git a/gcc/tree-vect-patterns.c b/gcc/tree-vect-patterns.c
index b575b456301..803de3fc287 100644
--- a/gcc/tree-vect-patterns.c
+++ b/gcc/tree-vect-patterns.c
@@ -1705,6 +1705,7 @@ vect_recog_over_widening_pattern (vec_info *vinfo,
   /* Apply the minimum efficient precision we just calculated.  */
   if (new_precision < min_precision)
     new_precision = min_precision;
+  new_precision = vect_element_precision (new_precision);
   if (new_precision >= TYPE_PRECISION (type))
     return NULL;
 
-- 
2.26.2