[Bug middle-end/18463] New: [4.0 Regression] Moving floating point through an integer register

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

The item "Moving floating point through integer registers" 
on http://gcc.gnu.org/projects/optimize.html shows how GCC 
can move a float array element via an integer register. 
 
Consider the following test case: 
 
void 
fcpy(float *restrict a,  float *restrict b, 
     float *restrict aa, float *restrict bb, int n) 
{ 
        int i; 
        for(i = 0; i < n; i++) { 
                aa[i]=a[i]; 
                bb[i]=b[i]; 
        } 
} 
 
GCC 3.3 produces the following code for the inner loop for 
-O2 -fomit-frame-pointer -fschedule-insns --std=c99: 
 
.L6: 
        movl    (%ebp,%ecx,4), %eax 
        movl    (%edi,%ecx,4), %edx 
        movl    %eax, (%esi,%ecx,4) 
        movl    %edx, (%ebx,%ecx,4) 
        incl    %ecx 
        cmpl    36(%esp), %ecx 
        jl      .L6 
 
GCC 4.0 (4.0.0 20041112) produces this piece of junk: 
 
.L4: 
        movl    20(%esp), %eax 
        leal    0(,%ebx,4), %edx 
        cmpl    %ebx, %ebp 
        movl    -4(%eax,%edx), %ecx 
        leal    1(%ebx), %eax 
        movl    %eax, %ebx 
        movl    %ecx, -4(%edi,%edx) 
        movl    24(%esp), %ecx 
        movl    -4(%edx,%ecx), %eax 
        movl    %eax, -4(%edx,%esi) 
        jg      .L4 
 
This is a bad regression from at least gcc 2.95 and gcc 3.1, 
as demonstraded on the projects/optimize.html page.

-- 
           Summary: [4.0 Regression] Moving floating point through an
                    integer register
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: middle-end
        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,jh at suse dot cz,zack
                    at codesourcery dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18463