diff mbox series

Combine new calculated ranges with existing range.

Message ID 4d5351a2-3776-e819-4186-11127ecb8269@redhat.com
State New
Headers show
Series Combine new calculated ranges with existing range. | expand

Commit Message

Andrew MacLeod Nov. 6, 2020, 7:27 p.m. UTC 
This patch fixed PR 97737 and 97741.

basically, when we re-calculate a range, intersect it with whatever we 
knew before so we dont lose any accumulated information.  PR97741 
details the specific case, but I was considering doing this anyway as it 
will allo us to retain any externally accumulated information that is 
known about an SSA_NAME which we would lose right now.

It wasnt really an issue before because the ranger never recalculated a 
range, but with the temporal cache allowing for follow on calculations 
it become more important.

bootstrapped on x86_64-pc-linux-gnu, no regressions. pushed.

Andrew
diff mbox series

Patch

commit 129e1a8a96d140150705fab30d25afb464eb1d99
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Fri Nov 6 14:14:46 2020 -0500

    Combine new calculated ranges with existing range.
    
    When a range is recalculated, retain what was previously known as IL changes
    can produce different results from un-executed code.   This also paves
    the way for external injection of ranges.
    
            gcc/
            PR tree-optimization/97737
            PR tree-optimization/97741
            * gimple-range.cc: (gimple_ranger::range_of_stmt): Intersect newly
            calculated ranges with the existing known global range.
            gcc/testsuite/
            * gcc.dg/pr97737.c: New.
            * gcc.dg/pr97741.c: New.

diff --git a/gcc/gimple-range.cc b/gcc/gimple-range.cc
index 0c8ec40448f..92a6335bec5 100644
--- a/gcc/gimple-range.cc
+++ b/gcc/gimple-range.cc
@@ -1026,8 +1026,14 @@  gimple_ranger::range_of_stmt (irange &r, gimple *s, tree name)
   if (m_cache.get_non_stale_global_range (r, name))
     return true;
 
-  // Otherwise calculate a new value and save it.
-  calc_stmt (r, s, name);
+  // Otherwise calculate a new value.
+  int_range_max tmp;
+  calc_stmt (tmp, s, name);
+
+  // Combine the new value with the old value.  This is required because
+  // the way value propagation works, when the IL changes on the fly we
+  // can sometimes get different results.  See PR 97741.
+  r.intersect (tmp);
   m_cache.set_global_range (name, r);
   return true;
 }
diff --git a/gcc/testsuite/gcc.dg/pr97737.c b/gcc/testsuite/gcc.dg/pr97737.c
new file mode 100644
index 00000000000..eef1c353191
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr97737.c
@@ -0,0 +1,16 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+int a = 1, b, c;
+
+void d() {
+  int e = 1;
+L1:
+  b = e;
+L2:
+  e = e / a;
+  if (!(e || c || e - 1))
+    goto L1;
+  if (!b)
+    goto L2;
+}
diff --git a/gcc/testsuite/gcc.dg/pr97741.c b/gcc/testsuite/gcc.dg/pr97741.c
new file mode 100644
index 00000000000..47115d31d4a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr97741.c
@@ -0,0 +1,17 @@ 
+/* { dg-do compile } */
+/* { dg-options "-Wall -Wextra -fno-strict-aliasing -fwrapv -Os -fno-toplevel-reorder -fno-tree-ccp -fno-tree-fre" } */
+
+short a = 0;
+long b = 0;
+char c = 0;
+void d() {
+  int e = 0;
+f:
+  for (a = 6; a;)
+    c = e;
+  e = 0;
+  for (; e == 20; ++e)
+    for (; b;)
+      goto f;
+}
+int main() { return 0; }