Re: [patch] Fix invalid GIMPLE out of SRA

[Richard Guenther <richard dot guenther at gmail dot com>]

On Wed, Mar 23, 2011 at 9:54 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
> Hi,
>
> this is a fallout of one of my gimplifier changes. ?For the attached testcase,
> the compiler generates invalid GIMPLE at -O1 or above:
>
> p.adb: In function 'P.F':
> p.adb:24:1: error: invalid operand in unary operation
> D.2361_107 = (integer[1:1] *) &*S15b.16_56[D.2327_91 ...]{lb: 1 sz: 4};
>
> ?if (!is_gimple_val (rhs1))
> ? ?{
> ? ? ?error ("invalid operand in unary operation");
> ? ? ?return true;
> ? ?}
>
> (gdb) p rhs_code
> $6 = NOP_EXPR
> (gdb) p debug_generic_expr(rhs1)
> &*S15b.16_56[D.2327_91 ...]{lb: 1 sz: 4}
>
> i.e ADDR_EXPR of ARRAY_RANGE_REF with non-constant operand #1.
>
> The invalid statement is generated by the early SRA pass:
>
> ?integer a1[1:1];
>
> ?VIEW_CONVERT_EXPR<integer[1:1]>(*S15b.16_56[D.2327_91 ...]{lb: 1 sz: 4}) =
> a1;
>
> is rewritten into:
>
> ?Created a replacement for a1 offset: 0, size: 32: a1$1
>
> ?D.2361_107 = (integer[1:1] *) &*S15b.16_56[D.2327_91 ...]{lb: 1 sz: 4};
> ?MEM[(integer[1:D.2312] *)D.2361_107] = a1$1_92;
>
>
> It turns out that the problematic NOP_EXPR is a useless type conversion emitted
> by build_fold_addr_expr: if you add a call to force_gimple_operand at the hot
> spot, it ends up removing the NOP_EXPR and nothing else. ?So the proposed fix
> is just to add a call to STRIP_USELESS_TYPE_CONVERSION there.
>
> Tested on i586-suse-linux, OK for the mainline?

Ok.

At some point I hope we get gimple variants for most of the tree
building helpers (that build_fold_addr_expr, and also fold_convert).

Thanks,
Richard.

>
> 2011-03-23 ?Eric Botcazou ?<ebotcazou@adacore.com>
>
> ? ? ? ?* tree-sra.c (build_ref_for_offset): Call STRIP_USELESS_TYPE_CONVERSION
> ? ? ? ?on the address built for a reference with variable offset.
>
>
> 2011-03-23 ?Eric Botcazou ?<ebotcazou@adacore.com>
>
> ? ? ? ?* gnat.dg/array15.ad[sb]: New test.
> ? ? ? ?* gnat.dg/array15_pkg.ads: New helper.
>
>
> --
> Eric Botcazou
>