[Bug target/21588] New: x86 machine builtins do not have any const/pure attributes set

["steven at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

Consider this snippet: 
 
typedef float v4sf __attribute__ ((vector_size (16))); 
float global; 
float 
waste_global (float p[4]) 
{ 
  __builtin_ia32_loadups (p); 
  global += 1.0; 
} 
 
GCC now thinks __builtin_ia32_loadups clobbers global: 
 
waste_global (pD.1564) 
{ 
  floatD.28 D.1568; 
  floatD.28 global.0D.1567; 
 
  # BLOCK 0 
  # PRED: ENTRY [100.0%]  (fallthru,exec) 
  #   globalD.1563_6 = V_MAY_DEF <globalD.1563_2>; 
  __builtin_ia32_loadups (pD.1564_1); 
  #   VUSE <globalD.1563_6>; 
  global.0D.1567_3 = globalD.1563; 
  D.1568_4 = global.0D.1567_3 + 1.0e+0; 
  #   globalD.1563_5 = V_MUST_DEF <globalD.1563_6>; 
  globalD.1563 = D.1568_4; 
  return; 
  # SUCC: EXIT [100.0%] 
 
} 
 
 
This is a bit silly, if we encourage people to use builtins instead 
of inline assembly.

-- 
           Summary: x86 machine builtins do not have any const/pure
                    attributes set
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: steven at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org,hubicka at gcc dot gnu
                    dot org,rth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21588