[gcc(refs/users/aldyh/heads/ranger-staging)] Adjusted and documented threading tests.

[gcc(refs/users/aldyh/heads/ranger-staging)] Adjusted and documented threading tests.

[Aldy Hernandez]

https://gcc.gnu.org/g:58b5c667ed3f1d1ef272349ade6563986209993e

commit 58b5c667ed3f1d1ef272349ade6563986209993e
Author: Aldy Hernandez <aldyh@redhat.com>
Date:   Fri Sep 18 15:26:41 2020 +0200

    Adjusted and documented threading tests.
    
    Adjusted ssa-dom-thread-[67].c so they match reality.  Documented why
    thread counts are different.
    
    Documented changes in pr77445-2.c, but I'm still not sure what the
    original failing message was checking for.

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c        |  4 +++
 gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-6.c | 38 ++++++++++++++++++++++--
 gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-7.c | 27 ++++++++++++-----
 3 files changed, 59 insertions(+), 10 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c
index 9c22c538da8..2b0e3878e3f 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr77445-2.c
@@ -124,6 +124,10 @@ enum STATES FMS( u8 **in , u32 *transitions) {
    to change decisions in switch expansion which in turn can expose new
    jump threading opportunities.  Skip the later tests on aarch64.  */
 /* { dg-final { scan-tree-dump "Jumps threaded: 1\[1-9\]" "thread1" } } */
+/* ?? I have no idea what this "Invalid sum" business was originally
+   checking for, but we are threading 6 more paths on x86_64 which is
+   obviously changing the IL in visible ways.  FWIW, we are getting 6
+   "Invalid sum" messages instead of 3.  */
 /* { dg-final { scan-tree-dump-times "Invalid sum" 3 "thread1" } } */
 /* { dg-final { scan-tree-dump-not "optimizing for size" "thread1" } } */
 /* { dg-final { scan-tree-dump-not "optimizing for size" "thread2" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-6.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-6.c
index 551fbac3dad..47b6acdfd96 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-6.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-6.c
@@ -1,7 +1,41 @@
 /* { dg-do compile } */
 /* { dg-options "-O2 -fdump-tree-thread1-details -fdump-tree-thread2-details" } */
-/* { dg-final { scan-tree-dump-times "FSM" 3 "thread1" } } */
-/* { dg-final { scan-tree-dump-times "FSM" 5 "thread2" } } */
+
+/* All the threads in the thread1 dump start on a X->BB12 edge, as can
+   be seen in the dump:
+
+     Registering FSM jump thread: (x, 12) incoming edge; ...
+     etc
+     etc
+
+   Before evrp went hybrid, we were threading paths that started at
+   the following edges:
+
+      Registering FSM jump thread: (10, 12) incoming edge
+      Registering FSM jump thread:  (6, 12) incoming edge
+      Registering FSM jump thread:  (9, 12) incoming edge
+
+   This was because the PHI at BB12 had constant values coming in from
+   BB10, BB6, and BB9:
+
+   # state_10 = PHI <state_11(7), 0(10), state_11(5), 1(6), state_11(8), 2(9), state_11(11)>
+
+   Now with the hybrid evrp, we get:
+
+   # state_10 = PHI <0(7), 0(10), state_11(5), 1(6), 0(8), 2(9), 1(11)>
+
+   Thus, we have 3 more paths that are known to be constant and can be
+   threaded.  Which means that by the second threading pass, we can
+   only find one profitable path.
+
+   For the record, all these extra constants are better paths coming
+   out of switches.  For example:
+
+     SWITCH_BB -> BBx -> BBy -> BBz -> PHI
+
+   We now know the value of the switch index at PHI.  */
+/* { dg-final { scan-tree-dump-times "FSM" 6 "thread1" } } */
+/* { dg-final { scan-tree-dump-times "FSM" 1 "thread2" } } */
 
 int sum0, sum1, sum2, sum3;
 int foo (char *s, char **ret)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-7.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-7.c
index a3395578f78..bad5bc1d003 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-7.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-7.c
@@ -1,20 +1,31 @@
 /* { dg-do compile } */
 /* { dg-options "-O2 -fdump-tree-thread1-stats -fdump-tree-thread2-stats -fdump-tree-dom2-stats -fdump-tree-thread3-stats -fdump-tree-dom3-stats -fdump-tree-vrp2-stats -fno-guess-branch-probability" } */
-/* { dg-final { scan-tree-dump "Jumps threaded: 16"  "thread1" } } */
-/* { dg-final { scan-tree-dump "Jumps threaded: 9" "thread2" } } */
+
+/* Here we have the same issue as was commented in ssa-dom-thread-6.c.
+   The PHI coming into the threader has a lot more constants, so the
+   threader can thread more paths.
+
+$ diff clean/a.c.105t.mergephi2 a.c.105t.mergephi2 
+252c252
+<   # s_50 = PHI <s_49(10), 5(14), s_51(18), s_51(22), 1(26), 1(29), 1(31), s_51(5), 4(12), 1(15), 5(17), 1(19), 3(21), 1(23), 6(25), 7(28), s_51(30)>
+---
+>   # s_50 = PHI <s_49(10), 5(14), 4(18), 5(22), 1(26), 1(29), 1(31), s_51(5), 4(12), 1(15), 5(17), 1(19), 3(21), 1(23), 6(25), 7(28), 7(30)>
+272a273
+
+  I spot checked a few and they all have the same pattern.  We are
+  basically tracking the switch index better through multiple
+  paths.  */
+
+/* { dg-final { scan-tree-dump "Jumps threaded: 19"  "thread1" } } */
+/* { dg-final { scan-tree-dump "Jumps threaded: 8" "thread2" } } */
 /* { dg-final { scan-tree-dump-not "Jumps threaded"  "dom2" } } */
+
 /* aarch64 has the highest CASE_VALUES_THRESHOLD in GCC.  It's high enough
    to change decisions in switch expansion which in turn can expose new
    jump threading opportunities.  Skip the later tests on aarch64.  */
 /* { dg-final { scan-tree-dump-not "Jumps threaded"  "dom3" { target { ! aarch64*-*-* } } } } */
 /* { dg-final { scan-tree-dump-not "Jumps threaded"  "vrp2" { target { ! aarch64*-*-* } } } } */
 
-/* Most architectures get 3 threadable paths here, whereas aarch64 and
-   possibly others get 5.  We really should rewrite threading tests to
-   test a specific IL sequence, not gobs of code whose IL can vary
-   from architecture to architecture.  */
-/* { dg-final { scan-tree-dump "Jumps threaded: \[35\]" "thread3" } } */
-
 enum STATE {
   S0=0,
   SI,