[gcc r12-3791] Set bound/cmp/control for until wrap loop.

[gcc r12-3791] Set bound/cmp/control for until wrap loop.

[Jiu Fu Guo]

https://gcc.gnu.org/g:3087d1b0a2cbe8880ccbbb67744726ff4e5d390e

commit r12-3791-g3087d1b0a2cbe8880ccbbb67744726ff4e5d390e
Author: Jiufu Guo <guojiufu@linux.ibm.com>
Date:   Wed Sep 22 13:20:29 2021 +0800

    Set bound/cmp/control for until wrap loop.
    
    In patch r12-3136, niter->control, niter->bound and niter->cmp are
    derived from number_of_iterations_lt.  While for 'until wrap condition',
    the calculation in number_of_iterations_lt is not align the requirements
    on the define of them and requirements in determine_exit_conditions.
    
    This patch calculate niter->control, niter->bound and niter->cmp in
    number_of_iterations_until_wrap.
    
    gcc/ChangeLog:
    
    2021-09-22  Jiufu Guo  <guojiufu@linux.ibm.com>
    
            PR tree-optimization/102087
            * tree-ssa-loop-niter.c (number_of_iterations_until_wrap):
            Update bound/cmp/control for niter.
    
    gcc/testsuite/ChangeLog:
    
    2021-09-22  Jiufu Guo  <guojiufu@linux.ibm.com>
    
            * gcc.dg/pr102087.c: New test.
            PR tree-optimization/102087

Diff:
---
 gcc/testsuite/gcc.dg/pr102087.c | 35 +++++++++++++++++++++++++++++++++++
 gcc/tree-ssa-loop-niter.c       | 16 +++++++++++++++-
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/pr102087.c b/gcc/testsuite/gcc.dg/pr102087.c
new file mode 100644
index 00000000000..5cd094fc097
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr102087.c
@@ -0,0 +1,35 @@
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+unsigned __attribute__ ((noinline))
+foo (int *__restrict__ a, int *__restrict__ b, unsigned l, unsigned n)
+{
+  while (n < ++l)
+    *a++ = *b++ + 1;
+  return l;
+}
+
+volatile int a[1];
+unsigned b;
+int c;
+
+int
+check ()
+{
+  int d;
+  for (; b > 1; b++)
+    for (c = 0; c < 2; c++)
+      for (d = 0; d < 2; d++)
+	a[0];
+  return 0;
+}
+
+char **clip_image_gfi_0;
+int clip_image_y, clip_image_shift;
+void
+clip_image ()
+{
+  for (; clip_image_y >= clip_image_shift; clip_image_y++)
+    clip_image_gfi_0[clip_image_shift]
+      = clip_image_gfi_0[clip_image_y];
+}
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index 7af92d1c893..75109407124 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -1482,7 +1482,7 @@ number_of_iterations_until_wrap (class loop *, tree type, affine_iv *iv0,
 				 affine_iv *iv1, class tree_niter_desc *niter)
 {
   tree niter_type = unsigned_type_for (type);
-  tree step, num, assumptions, may_be_zero;
+  tree step, num, assumptions, may_be_zero, span;
   wide_int high, low, max, min;
 
   may_be_zero = fold_build2 (LE_EXPR, boolean_type_node, iv1->base, iv0->base);
@@ -1557,6 +1557,20 @@ number_of_iterations_until_wrap (class loop *, tree type, affine_iv *iv0,
 
   niter->control.no_overflow = false;
 
+  /* Update bound and exit condition as:
+     bound = niter * STEP + (IVbase - STEP).
+     { IVbase - STEP, +, STEP } != bound
+     Here, biasing IVbase by 1 step makes 'bound' be the value before wrap.
+     */
+  niter->control.base = fold_build2 (MINUS_EXPR, niter_type,
+				     niter->control.base, niter->control.step);
+  span = fold_build2 (MULT_EXPR, niter_type, niter->niter,
+		      fold_convert (niter_type, niter->control.step));
+  niter->bound = fold_build2 (PLUS_EXPR, niter_type, span,
+			      fold_convert (niter_type, niter->control.base));
+  niter->bound = fold_convert (type, niter->bound);
+  niter->cmp = NE_EXPR;
+
   return true;
 }