[Bug target/123624] New: aarch64: Shrink wrapping incorrectly reduces streaming mode usage in locally streaming functions

[acarlotti at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123624

            Bug ID: 123624
           Summary: aarch64: Shrink wrapping incorrectly reduces streaming
                    mode usage in locally streaming functions
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: acarlotti at gcc dot gnu.org
  Target Milestone: ---

Shrink wrapping can incorrectly postpone a switch into streaming mode until
after instructions like cntd, whose result can depend on whether or not we're
in streaming mode.

The following test is miscompiled:


int foo(int x);// __arm_streaming;

__arm_locally_streaming
int bar(int x)
{
    if (x)
        return foo(3);
    return svcntd();
}


Shrink wrapping moves the prologue into the if (x) branch, leaving the cntd
instruction in !x branch executing in non-streaming mode.

I'll post a fix shortly.