Patchwork Reload related segfaults

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Submitter Alan Modra
Date Oct. 27, 2011, 2:59 a.m.
Message ID <20111027025956.GQ29439@bubble.grove.modra.org>
Download mbox | patch
Permalink /patch/122057/
State New
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Comments

Alan Modra - Oct. 27, 2011, 2:59 a.m.
Some recent patch has exposed a reload bug.  I'm seeing

libtool: compile:  /home/amodra/build/gcc-curr/./gcc/xgcc -B/home/amodra/build/gcc-curr/./gcc/ -B/home/amodra/gnu/powerpc-linux/bin/ -B/home/amodra/gnu/powerpc-linux/lib/ -isystem /home/amodra/gnu/powerpc-linux/include -isystem /home/amodra/gnu/powerpc-linux/sys-include -m64 -fPIC -mstrict-align -DHAVE_CONFIG_H -I. -I/home/amodra/src/gcc-current/libjava/classpath/native/fdlibm -I../../include -fexceptions -fasynchronous-unwind-tables -g -O2 -m64 -fPIC -mstrict-align -MT sf_fabs.lo -MD -MP -MF .deps/sf_fabs.Tpo -c /home/amodra/src/gcc-current/libjava/classpath/native/fdlibm/sf_fabs.c  -fPIC -DPIC -o .libs/sf_fabs.o
/home/amodra/src/gcc-current/libjava/classpath/native/fdlibm/sf_fabs.c: In function 'fabsf':
/home/amodra/src/gcc-current/libjava/classpath/native/fdlibm/sf_fabs.c:33:1: internal compiler error: Segmentation fault

(insn 11 9 15 2 (parallel [
            (set (subreg:SI (reg:SF 123 [ <retval> ]) 0)
                (and:SI (subreg:SI (reg:SF 33 1 [ x ]) 0)
                    (const_int 2147483647 [0x7fffffff])))
            (clobber (scratch:CC))
        ]) /home/amodra/src/gcc-current/libjava/classpath/native/fdlibm/sf_fabs.c:32 146 {andsi3_mc}
     (expr_list:REG_DEAD (reg:SF 33 1 [ x ])
        (nil)))

Reloads for insn # 11
Reload 0: GENERAL_REGS, RELOAD_FOR_INPUT_ADDRESS (opnum = 0), can't combine, secondary_reload_p
	reload_reg_rtx: (reg:SF 8 8)
Reload 1: GENERAL_REGS, RELOAD_FOR_OUTPUT_ADDRESS (opnum = 0), can't combine, secondary_reload_p
	reload_reg_rtx: (reg:SF 8 8)
Reload 2: reload_in (SF) = (reg:SF 33 1 [orig:123 <retval> ] [123])
	reload_out (SF) = (reg:SF 33 1 [orig:123 <retval> ] [123])
	NON_FLOAT_REGS, RELOAD_OTHER (opnum = 0)
	reload_in_reg: (reg:SF 33 1 [orig:123 <retval> ] [123])
	reload_out_reg: (reg:SF 33 1 [orig:123 <retval> ] [123])
	reload_reg_rtx: (reg:SF 10 10)
	secondary_in_reload = 0, secondary_out_reload = 1

Reload 3: reload_out (SI) = (subreg:SI (reg:SF 33 1 [orig:123 <retval> ] [123]) 0)
	GENERAL_REGS, RELOAD_FOR_OUTPUT (opnum = 0)
	reload_out_reg: (subreg:SI (reg:SF 33 1 [orig:123 <retval> ] [123]) 0)
	reload_reg_rtx: (reg:SI 9 9)
Reload 4: reload_in (SF) = (reg:SF 33 1 [ x ])
	GENERAL_REGS, RELOAD_FOR_INPUT (opnum = 1)
	reload_in_reg: (reg:SF 33 1 [ x ])
	reload_reg_rtx: (reg:SF 8 8)

Notice reload 3 has a subreg for reload_out.  We wind up in the
gen_reload code shown below, and try to use REGNO on a subreg, leading
to

(gdb) p debug_rtx(out)
(reg:DI -166922608)

Or at least, that's what you get after fixing print_rtx to not
segfault..  Bootstrap and regression test powerpc-linux in progress.
OK to apply, assuming no regressions?

	* reload1.c (gen_reload): Don't use REGNO on SUBREGs.
	* print-rtl.c (print_rtx): Don't segfault on negative regno.

Note that s/REGNO (in_rtx)/value/ in print_rtx is reasonable given
that REG in rtl.def has a format of "i00", so XINT (in_rtx, i) is
always XINT (in_rtx, 0) for a reg, which is equivalent to REGNO apart
from signedness.
David Miller - Oct. 27, 2011, 3:07 a.m.
From: Alan Modra <amodra@gmail.com>
Date: Thu, 27 Oct 2011 13:29:56 +1030

> Some recent patch has exposed a reload bug.  I'm seeing

I think this might be a side effect or Eric's recent changes,
CC:'d.
David Miller - Oct. 27, 2011, 6:40 a.m.
From: David Miller <davem@davemloft.net>
Date: Wed, 26 Oct 2011 23:07:11 -0400 (EDT)

> From: Alan Modra <amodra@gmail.com>
> Date: Thu, 27 Oct 2011 13:29:56 +1030
> 
>> Some recent patch has exposed a reload bug.  I'm seeing
> 
> I think this might be a side effect or Eric's recent changes,
> CC:'d.

Eric, I'm seeing a similar segmentation fault in reload on sparc64.
But it's in a slightly different place than Alan's crash.

Simply compile gcc.target/ultrasp12.c with "-m64 -O2 -mcpu=ultrasparc -mvis"
to see this.

The crash is in find_valid_class() called from push_reload(), via this
code block around line 1184 of reload.c:

      enum reg_class in_out_class
	= find_valid_class (outmode, GET_MODE (SUBREG_REG (out)),
			    subreg_regno_offset (REGNO (SUBREG_REG (out)),
						 GET_MODE (SUBREG_REG (out)),
						 SUBREG_BYTE (out),
						 GET_MODE (out)),
			    REGNO (SUBREG_REG (out)));

'out' is:

(subreg:DI (reg/v:V4QI 50 %f18 [orig:314 s2hi4_ ] [314]) 0)

so subreg_regno_offset() returns -1, and find_valid_class() isn't too happy
about getting "-1" for it's 'n' argument.

I suspect the test that you removed in order to fix rtl-optimization/46603
would guard against this happening.

And indeed, I confirmed that backing out the rtl-optimization/46603
fix makes the segmentation fault go away.
Alan Modra - Nov. 4, 2011, 1:32 p.m.
Ping http://gcc.gnu.org/ml/gcc-patches/2011-10/msg02429.html

Eric fixed the bootstrap breakage by another patch, but there is a
fairly obvious bug in gen_reload fixed by my patch.  I gave enough
contect in the diff that you don't even need to look at the file. :)
Eric Botcazou - Nov. 4, 2011, 4:51 p.m.
> OK to apply, assuming no regressions?
>
> 	* reload1.c (gen_reload): Don't use REGNO on SUBREGs.
> 	* print-rtl.c (print_rtx): Don't segfault on negative regno.

OK, thanks.

Patch

Index: gcc/reload1.c
===================================================================
--- gcc/reload1.c	(revision 180542)
+++ gcc/reload1.c	(working copy)
@@ -8588,28 +8588,28 @@  gen_reload (rtx out, rtx in, int opnum, 
 	   && reg_or_subregno (in) < FIRST_PSEUDO_REGISTER
 	   && (REG_P (out)
 	       || (GET_CODE (out) == SUBREG && REG_P (SUBREG_REG (out))))
 	   && reg_or_subregno (out) < FIRST_PSEUDO_REGISTER
 	   && SECONDARY_MEMORY_NEEDED (REGNO_REG_CLASS (reg_or_subregno (in)),
 				       REGNO_REG_CLASS (reg_or_subregno (out)),
 				       GET_MODE (out)))
     {
       /* Get the memory to use and rewrite both registers to its mode.  */
       rtx loc = get_secondary_mem (in, GET_MODE (out), opnum, type);
 
       if (GET_MODE (loc) != GET_MODE (out))
-	out = gen_rtx_REG (GET_MODE (loc), REGNO (out));
+	out = gen_rtx_REG (GET_MODE (loc), reg_or_subregno (out));
 
       if (GET_MODE (loc) != GET_MODE (in))
-	in = gen_rtx_REG (GET_MODE (loc), REGNO (in));
+	in = gen_rtx_REG (GET_MODE (loc), reg_or_subregno (in));
 
       gen_reload (loc, in, opnum, type);
       gen_reload (out, loc, opnum, type);
     }
 #endif
   else if (REG_P (out) && UNARY_P (in))
     {
       rtx insn;
       rtx op1;
       rtx out_moded;
       rtx set;
 
Index: gcc/print-rtl.c
===================================================================
--- gcc/print-rtl.c	(revision 180542)
+++ gcc/print-rtl.c	(working copy)
@@ -465,13 +465,12 @@  print_rtx (const_rtx in_rtx)
 	    int value = XINT (in_rtx, i);
 	    const char *name;
 
 #ifndef GENERATOR_FILE
-	    if (REG_P (in_rtx) && value < FIRST_PSEUDO_REGISTER)
-	      fprintf (outfile, " %d %s", REGNO (in_rtx),
-		       reg_names[REGNO (in_rtx)]);
+	    if (REG_P (in_rtx) && (unsigned) value < FIRST_PSEUDO_REGISTER)
+	      fprintf (outfile, " %d %s", value, reg_names[value]);
 	    else if (REG_P (in_rtx)
-		     && value <= LAST_VIRTUAL_REGISTER)
+		     && (unsigned) value <= LAST_VIRTUAL_REGISTER)
 	      {
 		if (value == VIRTUAL_INCOMING_ARGS_REGNUM)
 		  fprintf (outfile, " %d virtual-incoming-args", value);
 		else if (value == VIRTUAL_STACK_VARS_REGNUM)