[Bug middle-end/35309] New: Late struct expansion leads to missing PRE

[xinliangli at gmail dot com]

// Example: the load of structs at return is partially redundant

struct A {
  int a;
  int b;
  int c;
  int d;
} ag, ag2,ag3;


struct A foo(int n)
{
   if (n)
   {
     ag2 = ag;
   }

   return ag;
}

// Gcc generated assembly code:

foo:
.LFB2:
        testl   %edi, %edi
        je      .L2
        movq    ag(%rip), %rax
        movq    %rax, ag2(%rip)
        movq    ag+8(%rip), %rax
        movq    %rax, ag2+8(%rip)
.L2:
        movq    ag+8(%rip), %rdx
        movq    ag(%rip), %rax
        ret
.LFE2:


-- 
           Summary: Late struct expansion leads to missing PRE
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: xinliangli at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35309