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Date: Tue, 06 Mar 2007 00:29:00 -0000
Subject: [Bug target/31054]  New: 80387 constants not emitted in 64-bit mode.
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From: "pluto at agmk dot net" <gcc-bugzilla@gcc.gnu.org>
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$ cat fpu.c
long double emit_fldlg2()
{ return 0.3010299956639811952256464283594894482L; }
long double emit_fldln2()
{ return 0.6931471805599453094286904741849753009L; /* or M_LN2l */ }
long double emit_fldl2e()
{ return 1.4426950408889634073876517827983434472L; /* or M_LOG2El */ }
long double emit_fldl2t()
{ return 3.3219280948873623478083405569094566090L; }
long double emit_fldpi()
{ return 3.1415926535897932385128089594061862044L; /* or M_PIl */ }

for 32-bit mode we get nice output:

$ gcc fpu.c -O1 -c -m32 -fomit-frame-pointer && objdump -d fpu.o

00000000 <emit_fldlg2>:
   0:   d9 ec                   fldlg2
   2:   c3                      ret
00000003 <emit_fldln2>:
   3:   d9 ed                   fldln2
   5:   c3                      ret
00000006 <emit_fldl2e>:
   6:   d9 ea                   fldl2e
   8:   c3                      ret
00000009 <emit_fldl2t>:
   9:   d9 e9                   fldl2t
   b:   c3                      ret
0000000c <emit_fldpi>:
   c:   d9 eb                   fldpi
   e:   c3                      ret

for 64-bits mode we get only memory loads :/

$ gcc fpu.c -O1 -c -m64 && objdump -d fpu.o

0000000000000000 <emit_fldlg2>:
   0:   db 2d 00 00 00 00       fldt   0(%rip)        # 6 <emit_fldlg2+0x6>
   6:   c3                      retq
0000000000000007 <emit_fldln2>:
   7:   db 2d 00 00 00 00       fldt   0(%rip)        # d <emit_fldln2+0x6>
   d:   c3                      retq
000000000000000e <emit_fldl2e>:
   e:   db 2d 00 00 00 00       fldt   0(%rip)        # 14 <emit_fldl2e+0x6>
  14:   c3                      retq
0000000000000015 <emit_fldl2t>:
  15:   db 2d 00 00 00 00       fldt   0(%rip)        # 1b <emit_fldl2t+0x6>
  1b:   c3                      retq
000000000000001c <emit_fldpi>:
  1c:   db 2d 00 00 00 00       fldt   0(%rip)        # 22 <emit_fldpi+0x6>
  22:   c3                      retq


-- 
           Summary: 80387 constants not emitted in 64-bit mode.
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pluto at agmk dot net
GCC target triplet: x86_64-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31054