Re: [AARCH64, PATCH] Fix ICE in aarch64_float_const_representable_p

[Ramana Radhakrishnan <ramana.gcc@googlemail.com>]

On Fri, May 30, 2014 at 9:14 AM, Tom de Vries <Tom_deVries@mentor.com> wrote:
> Marcus,
>
> when building for aarch64-linux-gnu with --enable-checking=yes,rtl, I run
> into the following error:
> ...
> In file included from src/libgcc/libgcc2.c:56:0:
> src/libgcc/libgcc2.c: In function ‘__floattisf’:
> src/libgcc/libgcc2.h:200:20: internal compiler error: RTL check: expected
> code 'const_double' and not mode 'VOID', have code 'const_double' and mode
> 'VOID' in aarch64_float_const_representable_p, at
> config/aarch64/aarch64.c:8481
>  #define __NDW(a,b) __ ## a ## ti ## b
>                     ^
> src/libgcc/libgcc2.h:293:21: note: in expansion of macro ‘__NDW’
>  #define __floatdisf __NDW(float,sf)
>                      ^
> src/libgcc/libgcc2.c:1569:14: note: in expansion of macro ‘__floatdisf’
>  #define FUNC __floatdisf
>               ^
> src/libgcc/libgcc2.c:1579:1: note: in expansion of macro ‘FUNC’
>  FUNC (DWtype u)
>  ^
> 0xc1a278 rtl_check_failed_code_mode(rtx_def const*, rtx_code, machine_mode,
> bool, char const*, int, char const*)
>         src/gcc/rtl.c:833
> 0x1062b7b aarch64_float_const_representable_p(rtx_def*)
>         src/gcc/config/aarch64/aarch64.c:8481
> 0x1052ae2 aarch64_rtx_costs
>         src/gcc/config/aarch64/aarch64.c:5003
> 0x1059a9c aarch64_rtx_costs_wrapper
>         src/gcc/config/aarch64/aarch64.c:5804
> 0xc38f1a rtx_cost(rtx_def*, rtx_code, int, bool)
>         src/gcc/rtlanal.c:3878
> 0xb159a9 avoid_expensive_constant
>         src/gcc/optabs.c:1389
> 0xb15ca9 expand_binop_directly
>         src/gcc/optabs.c:1441
> 0xb161e7 expand_binop(machine_mode, optab_tag, rtx_def*, rtx_def*, rtx_def*,
> int, optab_methods)
>         src/gcc/optabs.c:1568
> 0x87f27f expand_expr_real_2(separate_ops*, rtx_def*, machine_mode,
> expand_modifier)
>         src/gcc/expr.c:9200
> 0x87fe4b expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
> expand_modifier, rtx_def**, bool)
>         src/gcc/expr.c:9388
> 0x879534 expand_expr_real(tree_node*, rtx_def*, machine_mode,
> expand_modifier, rtx_def**, bool)
>         src/gcc/expr.c:7921
> 0x79a720 expand_normal
>         src/gcc/expr.h:471
> 0x79cdb3 do_jump_by_parts_greater
>         src/gcc/dojump.c:741
> 0x79b682 do_jump_1(tree_code, tree_node*, tree_node*, rtx_def*, rtx_def*,
> int)
>         src/gcc/dojump.c:280
> 0x79a8ce jumpifnot_1(tree_code, tree_node*, tree_node*, rtx_def*, int)
>         src/gcc/dojump.c:138
> 0x700de4 expand_gimple_cond
>         src/gcc/cfgexpand.c:2145
> 0x70ed7f expand_gimple_basic_block
>         src/gcc/cfgexpand.c:5063
> 0x71189c execute
>         src/gcc/cfgexpand.c:5803
> Please submit a full bug report,
> with preprocessed source if appropriate.
> Please include the complete backtrace with any bug report.
> See <http://gcc.gnu.org/bugs.html> for instructions.
> ...
>
> We assert here during REAL_VALUE_FROM_CONST_DOUBLE because x has VOIDmode,
> which means it has integer rather than floating point type:
> ...
> bool
> aarch64_float_const_representable_p (rtx x)
> {
>   /* This represents our current view of how many bits
>      make up the mantissa.  */
>   int point_pos = 2 * HOST_BITS_PER_WIDE_INT - 1;
>   int exponent;
>   unsigned HOST_WIDE_INT mantissa, mask;
>   REAL_VALUE_TYPE r, m;
>   bool fail;
>
>   if (!CONST_DOUBLE_P (x))
>     return false;
>
>   REAL_VALUE_FROM_CONST_DOUBLE (r, x);
> ...
>
> Attached patch fixes the ICE by handling the case that x is VOIDmode, and
> allows me to complete the build.
>

IIUC it would be better to shift the AArch64 port to
TARGET_SUPPORTS_WIDE_INT and not worry about x being VOIDmode at all.
In this case we should not have any const_double's containing
integers.

I have a couple of patches in testing that did this but with all the
other breakages in AArch64 and ARM land in the past couple of weeks I
have been unable to submit this.

regards
Ramana

> OK for trunk if build and test succeeds?
>
> I think the call site in aarch64_rtx_costs may need a separate fix.
>
> Thanks,
> - Tom