From 491e57451df47cda88f658601a92d6d006ae09d7 Mon Sep 17 00:00:00 2001
From: Tamar Christina <tamar.christina@arm.com>
Date: Tue, 13 Feb 2024 11:04:38 +0000
Subject: [PATCH] middle-end: update vector loop upper bounds when early break
vect [PR113734]
When doing early break vectorization we should treat the final iteration as
possibly being partial. This so that when we calculate the vector loop upper
bounds we take into account that final iteration could have done some work.
The attached testcase shows that if we don't then cunroll may unroll the loop an
if the upper bound is wrong we lose a vector iteration.
This is similar to how we adjust the scalar loop bounds for the PEELED case.
gcc/ChangeLog:
PR tree-optimization/113734
* tree-vect-loop.cc (vect_transform_loop): Treat the final iteration of
an early break loop as partial.
gcc/testsuite/ChangeLog:
PR tree-optimization/113734
* gcc.dg/vect/vect-early-break_117-pr113734.c: New test.
---
.../vect/vect-early-break_117-pr113734.c | 37 +++++++++++++++++++
gcc/tree-vect-loop.cc | 3 +-
2 files changed, 39 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c
diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c b/gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c
new file mode 100644
index 000000000000..36ae09483dfd
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c
@@ -0,0 +1,37 @@
+/* { dg-add-options vect_early_break } */
+/* { dg-require-effective-target vect_early_break_hw } */
+/* { dg-require-effective-target vect_int } */
+/* { dg-additional-options "-O3" } */
+
+/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
+
+#include "tree-vect.h"
+
+#define N 306
+#define NEEDLE 136
+
+int table[N];
+
+__attribute__ ((noipa))
+int foo (int i, unsigned short parse_tables_n)
+{
+ parse_tables_n >>= 9;
+ parse_tables_n += 11;
+ while (i < N && parse_tables_n--)
+ table[i++] = 0;
+
+ return table[NEEDLE];
+}
+
+int main ()
+{
+ check_vect ();
+
+ for (int j = 0; j < N; j++)
+ table[j] = -1;
+
+ if (foo (0, 0xFFFF) != 0)
+ __builtin_abort ();
+
+ return 0;
+}
diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index 04f4b5b6b2fa..367077965fd9 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -12174,7 +12174,8 @@ vect_transform_loop (loop_vec_info loop_vinfo, gimple *loop_vectorized_call)
/* True if the final iteration might not handle a full vector's
worth of scalar iterations. */
bool final_iter_may_be_partial
- = LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo);
+ = LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo)
+ || LOOP_VINFO_EARLY_BREAKS (loop_vinfo);
/* The minimum number of iterations performed by the epilogue. This
is 1 when peeling for gaps because we always need a final scalar
iteration. */
--
GitLab