[gcc r13-3434] Restore 'libgomp.oacc-c-c++-common/nvptx-sese-1.c' SESE regions checking [PR107195, PR107344]

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:a9de836c2b22f878cff592b96e11c1b95d4d36ee

commit r13-3434-ga9de836c2b22f878cff592b96e11c1b95d4d36ee
Author: Thomas Schwinge <thomas@codesourcery.com>
Date:   Sun Oct 16 00:07:20 2022 +0200

    Restore 'libgomp.oacc-c-c++-common/nvptx-sese-1.c' SESE regions checking [PR107195, PR107344]
    
    That is, adjust for optimization introduced with recent
    commit r13-3217-gc4d15dddf6b9eacb36f535807ad2ee364af46e04
    "[PR107195] Set range to zero when nonzero mask is 0", where GCC now
    understands that after 'r *= 2;', 'r & 1' will never hold here, and thus
    transforms/optimizes/"disturbs" the original code such that GCC/nvptx's later
    "Neuter whole SESE regions" optimization no longer is applicable to it:
    
        UNSUPPORTED: libgomp.oacc-c/../libgomp.oacc-c-c++-common/nvptx-sese-1.c -DACC_DEVICE_TYPE_nvidia=1 -DACC_MEM_SHARED=0 -foffload=nvptx-none  -O0
        PASS: libgomp.oacc-c/../libgomp.oacc-c-c++-common/nvptx-sese-1.c -DACC_DEVICE_TYPE_nvidia=1 -DACC_MEM_SHARED=0 -foffload=nvptx-none  -O2  (test for excess errors)
        PASS: libgomp.oacc-c/../libgomp.oacc-c-c++-common/nvptx-sese-1.c -DACC_DEVICE_TYPE_nvidia=1 -DACC_MEM_SHARED=0 -foffload=nvptx-none  -O2  execution test
        [-PASS:-]{+FAIL:+} libgomp.oacc-c/../libgomp.oacc-c-c++-common/nvptx-sese-1.c -DACC_DEVICE_TYPE_nvidia=1 -DACC_MEM_SHARED=0 -foffload=nvptx-none  -O2   scan-nvptx-none-offload-rtl-dump mach "SESE regions:.* [0-9]+{[0-9]+->[0-9]+(\\.[0-9]+)+}"
    
    Same for C++.
    
    It's unclear to me if this is an actual "problem", which optimization is "more
    important", so I've filed PR107344 "GCC/nvptx SESE region optimization" to
    capture this question, and here restore what we intend to be testing (to my
    understanding) in 'libgomp.oacc-c-c++-common/nvptx-sese-1.c'.
    
            PR tree-optimization/107195
            PR target/107344
            libgomp/
            * testsuite/libgomp.oacc-c-c++-common/nvptx-sese-1.c: Restore SESE
            regions checking.

Diff:
---
 libgomp/testsuite/libgomp.oacc-c-c++-common/nvptx-sese-1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libgomp/testsuite/libgomp.oacc-c-c++-common/nvptx-sese-1.c b/libgomp/testsuite/libgomp.oacc-c-c++-common/nvptx-sese-1.c
index 9583265c775..6507e1affb0 100644
--- a/libgomp/testsuite/libgomp.oacc-c-c++-common/nvptx-sese-1.c
+++ b/libgomp/testsuite/libgomp.oacc-c-c++-common/nvptx-sese-1.c
@@ -22,7 +22,7 @@ int main ()
     if (foo (r))
       r *= 2;
 
-    if (r & 1) /* to here. */
+    if (r & 8) /* to here. */
 #pragma acc loop vector reduction (+:r)
       for (int i = 00; i < 40; i++)
 	r += i;