[Bug target/68879] New: PowerPC: SImode cstore optimisation produces bad code

[anton at samba dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68879

            Bug ID: 68879
           Summary: PowerPC: SImode cstore optimisation produces bad code
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anton at samba dot org
  Target Milestone: ---

Created attachment 37017
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37017&action=edit
Test case

csmith found an issue that bisects to "rs6000: Optimise SImode cstore on
64-bit"

Attached is a simplified test case. A diff shows:

-       addi 9,10,2
-       orc 9,9,10
-       srwi 9,9,31

+       subf 9,9,6
+       srdi 9,9,63
+       xori 9,9,0x1