Re: optimization/9566: Inline function produces much worse code than manual inlining.

[Andrew Pinski <pinskia@physics.uc.edu>]

The following reply was made to PR optimization/9566; it has been noted by GNATS.

From: Andrew Pinski <pinskia@physics.uc.edu>
To: gcc-gnats@gcc.gnu.org, osv@javad.ru, gcc-bugs@gcc.gnu.org,
   nobody@gcc.gnu.org, gcc-prs@gcc.gnu.org
Cc: Andrew Pinski <pinskia@physics.uc.edu>
Subject: Re: optimization/9566: Inline function produces much worse code than manual inlining.
Date: Mon, 14 Apr 2003 19:35:58 -0400

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit- 
 trail&database=gcc&pr=9566
 
 The problem is because inlining causes a temporary variable which  
 causes this and causes it to spill to the stack.
 
 struct A {
    char const* src;
    char* dest;
    void copy() { *++dest = *++src; }
 };
 
 void g1() {
    A a;
    for(int i = 0; i < 10; ++i)
      a.copy();
 }
 
 void g2() {
    A a;
    for(int i = 0; i < 10; ++i)
        *++a.dest = *++a.src;
 }
 
 void g3() {
    A a;
    for(int i = 0; i < 10; ++i)
    {
      struct A b = a;
      {
        *++b.dest = *++b.src;
      }
      a = b;
    }
 }
 
 Note here g3 and g1 produce the same asm on PPC.
 
 Thanks,
 Andrew Pinski