[Bug target/124637] New: powerpc64: invalid code while passing a struct via register

[gcc at breakpoint dot cc via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124637

            Bug ID: 124637
           Summary: powerpc64: invalid code while passing a struct via
                    register
           Product: gcc
           Version: 15.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc at breakpoint dot cc
  Target Milestone: ---

Created attachment 64027
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64027&action=edit
Archive with testcase and compile script

OpenSSL has struct such as
  typedef struct {
      uint16_t kem_id;
      uint16_t kdf_id;
      uint16_t aead_id;
  } OSSL_HPKE_SUITE;

which is then passed argument. For the content { 0x20, 1, 1 } the compiler
produces the following opcodes:
         lis 9,0x20
         lis 4,0x1
         ori 9,9,0x1
         rldimi 4,9,32,0

which ends with r4 = 0x0020_0001_0000_0000
Correct would be:    0x0000_0020_0001_0001

powerpc64-linux-gnu is affected with -O1+, -O0 is fine.
powerpc64le-linux-gnu is not affected but it does not use rldimi. 

I'm attaching a testcase to
$ ./tc-comp.sh && ./m-0 && ./m-2 
20 1 1
1 1 0

The output should "20 1 1" from both m-0 (compiled at -O0) and m-2 (compiled at
-O2)

Sebastian