> -----Original Message-----
> From: Kyrylo Tkachov
> Sent: 27 February 2015 14:30
> To: Kyrylo Tkachov; GCC Patches
> Cc: Ramana Radhakrishnan; Richard Earnshaw
> Subject: RE: [PATCH][ARM] PR target/64600 Fix another ICE with -
> mtune=xscale: properly sign-extend mask during constant splitting
> 
> On 03/02/15 15:18, Kyrill Tkachov wrote:
> > Hi all,
> >
> > The ICE in this PR occurs when -mtune=xscale triggers a particular
> > path through arm_gen_constant during expand that creates a 0xfffff00f
> > mask but for a 64-bit HOST_WIDE_INT doesn't sign extend it into
> > 0xfffffffffffff00f that signifies the required -4081. It leaves it as
> > 0xfffff00f (4294963215) that breaks when later combine tries to
> > perform an SImode bitwise AND using the wide-int machinery.
> >
> > I think the correct approach here is to use trunc_int_for_mode that
> > correctly sign-extends the constant so that it is properly represented
> > by a HOST_WIDE_INT for the required mode.
> >
> > Bootstrapped and tested arm-none-linux-gnueabihf with -mtune=xscale in
> > BOOT_CFLAGS.
> >
> > The testcase triggers for -mcpu=xscale and all slowmul targets because
> > they are the only ones that have the constant_limit tune parameter set
> > to anything >1 which is required to follow this particular path
> > through arm_split_constant. Also, the rtx costs can hide this ICE
> > sometimes.
> >
> > Ok for trunk?
> >
> > Thanks,
> > Kyrill
> >
> > 2015-02-03  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
> >
> >      PR target/64600
> >      * config/arm/arm.c (arm_gen_constant, AND case): Call
> >      trunc_int_for_mode when constructing AND mask.
> >
> > 2015-02-03  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
> >
> >      PR target/64600
> >      * gcc.target/arm/pr64600_1.c: New test.
> > arm-xscale-wide.patch
> > commit 52388a359dd65276bccfac499a2fd9e406fbe1a8
> > Author: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
> > Date:   Tue Jan 20 11:21:34 2015 +0000
> >
> >     [ARM] Fix ICE due to arm_gen_constant not sign_extending
> >
> > diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c index
> > db4834b..d0f3a52 100644
> > --- a/gcc/config/arm/arm.c
> > +++ b/gcc/config/arm/arm.c
> > @@ -4709,19 +4709,20 @@ arm_gen_constant (enum rtx_code code,
> > machine_mode mode, rtx cond,
> >
> >  	  if ((remainder | shift_mask) != 0xffffffff)
> >  	    {
> > +	      HOST_WIDE_INT new_val
> > +	        = trunc_int_for_mode (remainder | shift_mask, mode);
> 
> Offlist, Richard mentioned that trunc_int_for_mode may pessimize codegen
> for HImode values due to excessive setting of bits and using
> ARM_SIGN_EXTEND might be preferable.
> I've tried that and it does fix the ICE and goes through testing ok. Bootstrap
> still ongoing.
> I didn't perform any code quality investigation. Richard, are there any
> particular code sequences  that you'd like us to investigate here?
> 

Here's the alternative version using ARM_SIGN_EXTEND if you want to have  a look.
Thanks,
Kyrill


2015-03-03  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

       PR target/64600
       * config/arm/arm.c (arm_gen_constant, AND case): Use
       ARM_SIGN_EXTEND when constructing AND mask.

2015-03-03  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

       PR target/64600
       * gcc.target/arm/pr64600_1.c: New test.

> Thanks,
> Kyrill
> 
> >
> > +
> >  	      if (generate)
> >  		{
> >  		  rtx new_src = subtargets ? gen_reg_rtx (mode) : target;
> > -		  insns = arm_gen_constant (AND, mode, cond,
> > -					    remainder | shift_mask,
> > +		  insns = arm_gen_constant (AND, SImode, cond, new_val,
> >  					    new_src, source, subtargets, 1);
> >  		  source = new_src;
> >  		}
> >  	      else
> >  		{
> >  		  rtx targ = subtargets ? NULL_RTX : target;
> > -		  insns = arm_gen_constant (AND, mode, cond,
> > -					    remainder | shift_mask,
> > +		  insns = arm_gen_constant (AND, mode, cond, new_val,
> >  					    targ, source, subtargets, 0);
> >  		}
> >  	    }
> > @@ -4744,12 +4745,13 @@ arm_gen_constant (enum rtx_code code,
> > machine_mode mode, rtx cond,
> >
> >  	  if ((remainder | shift_mask) != 0xffffffff)
> >  	    {
> > +	      HOST_WIDE_INT new_val
> > +	        = trunc_int_for_mode (remainder | shift_mask, mode);
> >  	      if (generate)
> >  		{
> >  		  rtx new_src = subtargets ? gen_reg_rtx (mode) : target;
> >
> > -		  insns = arm_gen_constant (AND, mode, cond,
> > -					    remainder | shift_mask,
> > +		  insns = arm_gen_constant (AND, mode, cond, new_val,
> >  					    new_src, source, subtargets, 1);
> >  		  source = new_src;
> >  		}
> > @@ -4757,8 +4759,7 @@ arm_gen_constant (enum rtx_code code,
> machine_mode mode, rtx cond,
> >  		{
> >  		  rtx targ = subtargets ? NULL_RTX : target;
> >
> > -		  insns = arm_gen_constant (AND, mode, cond,
> > -					    remainder | shift_mask,
> > +		  insns = arm_gen_constant (AND, mode, cond, new_val,
> >  					    targ, source, subtargets, 0);
> >  		}
> >  	    }
> > diff --git a/gcc/testsuite/gcc.target/arm/pr64600_1.c
> > b/gcc/testsuite/gcc.target/arm/pr64600_1.c
> > new file mode 100644
> > index 0000000..6ba3fa2
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/pr64600_1.c
> > @@ -0,0 +1,15 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -mtune=xscale" } */
> > +
> > +typedef unsigned int speed_t;
> > +typedef unsigned int tcflag_t;
> > +
> > +struct termios {
> > + tcflag_t c_cflag;
> > +};
> > +
> > +speed_t
> > +cfgetospeed (const struct termios *tp) {
> > +  return tp->c_cflag & 010017;
> > +}
>