RE: [PING] PR middle-end/95126: Expand small const structs as immediate constants

["Roger Sayle" <roger@nextmovesoftware.com>]

Hi Rainer (and Andreas),
My sincere apologies for the breakage.  I'm currently regression testing a
solution to the ICEs introduced by my "small const struct" patch, which
fingers-crossed might also fix this Ada bootstrap.  For a while when
Rainer also reported the bootstrap failure is visible, on
x86_64-pc-linux-gnu,
I thought I'd be able to diagnose and fix the issue myself, but alas my
--enable-languages="all" builds (still) fail earlier with:

gcc -std=gnu99 -c -g  -gnatpg -gnatwns -gnata -W -Wall -I- -I.
-Iada/generated -Iada -I../../gcc/gcc/ada ../../gcc/gcc/ada/osint.adb -o
ada/osint.o
osint.adb:438:31: "strlen" not declared in "CRTL"
osint.adb:441:14: "strncpy" not declared in "CRTL"
osint.adb:675:21: "strlen" not declared in "CRTL"
osint.adb:728:16: "Open_Append" is undefined
osint.adb:1108:41: "int64" not declared in "CRTL"
osint.adb:3144:28: "strlen" not declared in "CRTL"
osint.adb:3147:11: "strncpy" not declared in "CRTL"

The one experiment I'd like to be able to try, to investigate the cause/cure
of this, is:

diff --git a/gcc/calls.cc b/gcc/calls.cc
index a4336c1..05fdd24 100644
--- a/gcc/calls.cc
+++ b/gcc/calls.cc
@@ -2177,7 +2177,7 @@ load_register_parameters (struct arg_data *args, int
num_a
             VAR_DECL with a simple constructor, expand that constructor
             via a pseudo rather than read from (possibly misaligned)
             memory.  PR middle-end/95126.  */
-         else if (nregs == 1
+         else if (0 && nregs == 1
                   && partial == 0
                   && !args[i].pass_on_stack
                   && VAR_P (tree_value)

My "small const structs" patch affected code generation in three places, and
identifying
which of these is causing the miscompilation issue for gnat will help narrow
down the
problem, or worst case allow reverting less of the problematic patch.

Again my deep apologies for the breakage.  Hopefully the fix I'm testing
will cure this as
well (but an ICE is different symptom to a silent miscompilation).

Sorry again,
Roger
--

> -----Original Message-----
> From: Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>
> Sent: 05 June 2022 21:31
> To: Andreas Schwab <schwab@linux-m68k.org>
> Cc: Roger Sayle <roger@nextmovesoftware.com>; gcc-patches@gcc.gnu.org
> Subject: Re: [PING] PR middle-end/95126: Expand small const structs as
> immediate constants
> 
> Andreas Schwab <schwab@linux-m68k.org> writes:
> 
> > This breaks Ada on aarch64 in stage3, probably a miscompiled stage2
> > compiler.  For example:
> >
> > /opt/gcc/gcc-20220605/Build/./prev-gcc/xgcc
> > -B/opt/gcc/gcc-20220605/Build/./prev-gcc/
> > -B/usr/aarch64-suse-linux/bin/ -B/usr/aarch64-suse-linux/bin/
> > -B/usr/aarch64-suse-linux/lib/ -isystem
> > /usr/aarch64-suse-linux/include -isystem
> > /usr/aarch64-suse-linux/sys-include -fchecking=1 -c -g -O2
> > -fchecking=1 -gnatpg -gnata -W -Wall -nostdinc -I- -I. -Iada/generated
> > -Iada -I../../gcc/ada -Iada/libgnat -I../../gcc/ada/libgnat
> > -Iada/gcc-interface -I../../gcc/ada/gcc-interface
> > ../../gcc/ada/spark_xrefs.adb -o ada/spark_xrefs.o
> > +===========================GNAT BUG
> > +DETECTED==============================+
> > | 13.0.0 20220605 (experimental) [master ad6919374be]
(aarch64-suse-linux)
> |
> > | Assert_Failure failed precondition from sinfo-nodes.ads:5419
|
> > | Error detected at types.ads:53:28
|
> > | Compiling ../../gcc/ada/spark_xrefs.adb
|
> > | Please submit a bug report; see https://gcc.gnu.org/bugs/ .
|
> > | Use a subject line meaningful to you and us to track the bug.
|
> > | Include the entire contents of this bug box in the report.
|
> > | Include the exact command that you entered.
|
> > | Also include sources listed below.
|
> >
> +================================================================
> =====
> > +=====+
> 
> Confirmed: this also happens on i386-pc-solaris2.11,
sparc-sun-solaris2.11, and
> x86_64-pc-linux-gnu.