Re: [PATCH 29/31] PDP11: Use `const_double_zero' to express double zero constant

[Martin Liška]

On 11/20/20 4:36 AM, Maciej W. Rozycki wrote:

We do not define a comparison operation between floating-point and
integer data, including integer zero constant.  Consequently the RTL
instruction stream presented to the post-reload comparison elimination
pass will include, where applicable, floating-point comparison insns
against `const_double:DF 0.0 [0x0.0p+0]' rather than `const_int 0 [0]',
meaning that the latter expression will not match when used in machine
description.

Use `const_double_zero' then for the relevant patterns to match the
intended RTL instructions.

        gcc/
        * config/pdp11/pdp11.md (fcc_cc, fcc_ccnz): Use
        `const_double_zero' to express double zero constant.
---
  gcc/config/pdp11/pdp11.md | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gcc/config/pdp11/pdp11.md b/gcc/config/pdp11/pdp11.md
index 7a4d50fdba9..cdef49f3979 100644
--- a/gcc/config/pdp11/pdp11.md
+++ b/gcc/config/pdp11/pdp11.md
@@ -105,7 +105,7 @@ (define_subst "fcc_cc"
     (clobber (reg FCC_REGNUM))]
    ""
    [(set (reg:CC FCC_REGNUM)
-       (compare:CC (match_dup 1) (const_int 0)))
+       (compare:CC (match_dup 1) (const_double_zero)))
     (set (match_dup 0) (match_dup 1))])

(define_subst "fcc_ccnz"

@@ -113,7 +113,7 @@ (define_subst "fcc_ccnz"
     (clobber (reg FCC_REGNUM))]
    ""
    [(set (reg:CCNZ FCC_REGNUM)
-       (compare:CCNZ (match_dup 1) (const_int 0)))
+       (compare:CCNZ (match_dup 1) (const_double_zero)))
     (set (match_dup 0) (match_dup 1))])

(define_subst_attr "cc_cc" "cc_cc" "_nocc" "_cc")

Hello.

If I see correctly, starting from this revision I can't compile a cross
compiler of x86_64-linux-gnu:

../configure --target=pdp11-aout --disable-bootstrap --enable-languages=c,c++ 
--disable-multilib  --enable-obsolete

$ make
build/genemit ../../gcc/common.md ../../gcc/config/pdp11/pdp11.md \
  insn-conditions.md > tmp-emit.c
genemit: Internal error: abort in gen_exp, at genemit.c:202
make: *** [Makefile:2427: s-emit] Error 1

$ Breakpoint 1, fancy_abort (file=0x435238 "../../gcc/genemit.c", line=202, func=0x435230 
"gen_exp") at ../../gcc/errors.c:133
133       internal_error ("abort in %s, at %s:%d", func, trim_filename (file), 
line);
(gdb) bt
#0  fancy_abort (file=0x435238 "../../gcc/genemit.c", line=202, func=0x435230 
"gen_exp") at ../../gcc/errors.c:133
#1  0x0000000000402e4b in gen_exp (x=0x470de0, subroutine_type=DEFINE_INSN, used=0x4aa4b0 
"", info=0x7fffffffdea0) at ../../gcc/genemit.c:202
#2  0x0000000000402f68 in gen_exp (x=0x4d6c70, subroutine_type=DEFINE_INSN, used=0x4aa4b0 
"", info=0x7fffffffdea0) at ../../gcc/genemit.c:227
#3  0x0000000000402f68 in gen_exp (x=0x4d6c50, subroutine_type=DEFINE_INSN, used=0x4aa4b0 
"", info=0x7fffffffdea0) at ../../gcc/genemit.c:227
#4  0x000000000040307d in gen_exp (x=0x4aa490, subroutine_type=DEFINE_INSN, used=0x4aa4b0 
"", info=0x7fffffffdea0) at ../../gcc/genemit.c:255
#5  0x00000000004036c1 in gen_insn (info=0x7fffffffdea0) at 
../../gcc/genemit.c:435
#6  0x0000000000404930 in main (argc=3, argv=0x7fffffffdfc8) at 
../../gcc/genemit.c:911

Can you please take a look?
Thanks,
Martin