[gcc(refs/users/tnfchris/heads/gcc-14-early-break)] Fix scale_loop_frequencies segfault on multiple-exits

[gcc(refs/users/tnfchris/heads/gcc-14-early-break)] Fix scale_loop_frequencies segfault on multiple-exits

[Tamar Christina]

https://gcc.gnu.org/g:c3c010cf7ac9e9c3d600466987c4dd98f253ffd4

commit c3c010cf7ac9e9c3d600466987c4dd98f253ffd4
Author: Tamar Christina <tamar.christina@arm.com>
Date:   Wed Jun 28 13:41:38 2023 +0100

    Fix scale_loop_frequencies segfault on multiple-exits
    
    There's an existing bug in loop frequency scaling where the if statement checks
    to see if there's a single exit, and records an dump file note but then
    continues.
    
    It then tries to access the null pointer, which of course fails.
    
    For multiple loop exists it's not really clear how to scale the exit
    probablities as it's really unknown which exit is most probably.
    
    For that reason I ignore the exit edges during scaling but still adjust the
    loop body.
    
    gcc/ChangeLog:
    
            * cfgloopmanip.cc (scale_loop_frequencies): Fix typo.
            (scale_loop_profile): Don't access null pointer.

Diff:
---
 gcc/cfgloopmanip.cc | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/gcc/cfgloopmanip.cc b/gcc/cfgloopmanip.cc
index 6e09dcbb0b1..b10ef3d2be8 100644
--- a/gcc/cfgloopmanip.cc
+++ b/gcc/cfgloopmanip.cc
@@ -501,7 +501,7 @@ scale_loop_frequencies (class loop *loop, profile_probability p)
 /* Scale profile in LOOP by P.
    If ITERATION_BOUND is non-zero, scale even further if loop is predicted
    to iterate too many times.
-   Before caling this function, preheader block profile should be already
+   Before calling this function, preheader block profile should be already
    scaled to final count.  This is necessary because loop iterations are
    determined by comparing header edge count to latch ege count and thus
    they need to be scaled synchronously.  */
@@ -597,14 +597,14 @@ scale_loop_profile (class loop *loop, profile_probability p,
       /* If latch exists, change its count, since we changed
 	 probability of exit.  Theoretically we should update everything from
 	 source of exit edge to latch, but for vectorizer this is enough.  */
-      if (loop->latch && loop->latch != e->src)
+      if (e && loop->latch && loop->latch != e->src)
 	loop->latch->count += count_delta;
 
       /* Scale the probabilities.  */
       scale_loop_frequencies (loop, p);
 
       /* Change latch's count back.  */
-      if (loop->latch && loop->latch != e->src)
+      if (e && loop->latch && loop->latch != e->src)
 	loop->latch->count -= count_delta;
 
       if (dump_file && (dump_flags & TDF_DETAILS))