[Bug target/108048] New: PPCLE: gcc does not recognize that lbzx does zero extend

[jens.seifert at de dot ibm.com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108048

            Bug ID: 108048
           Summary: PPCLE: gcc does not recognize that lbzx does zero
                    extend
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jens.seifert at de dot ibm.com
  Target Milestone: ---

extern unsigned char magic1[256];

unsigned int hash(const unsigned char inp[4])
{
   const unsigned long long INIT = 0x1ULL;
   unsigned long long h1 = INIT;
   h1 = magic1[((unsigned long long)inp[0]) ^ h1];
   h1 = magic1[((unsigned long long)inp[1]) ^ h1];
   h1 = magic1[((unsigned long long)inp[2]) ^ h1];
   h1 = magic1[((unsigned long long)inp[3]) ^ h1];
   return h1;
}

Generates:

hash(unsigned char const*):
.LCF0:
        addi 2,2,.TOC.-.LCF0@l
        lbz 9,0(3)
        addis 10,2,.LC0@toc@ha
        ld 10,.LC0@toc@l(10)
        lbz 6,1(3)
        lbz 7,2(3)
        lbz 8,3(3)
        xori 9,9,0x1
        lbzx 9,10,9
        xor 9,9,6
        rlwinm 9,9,0,0xff <= unnecessary
        lbzx 9,10,9
        xor 9,9,7
        rlwinm 9,9,0,0xff <= unnecessary
        lbzx 9,10,9
        xor 9,9,8
        rlwinm 9,9,0,0xff <= unnecessary
        lbzx 3,10,9
        blr


All XOR operations are done in unsigned long long (64-bit). gcc adds
unnecessary rlwinm. lbz and lbzx does zero extension (no cleanup of upper bits
required).