[PATCH 0/2] Zext/sext elimination using value range

[Kugan <kugan.vivekanandarajah@linaro.org>]

Hi,

This patch series (2) implements zext/sext extension elimination using
value ranges stored in SSA. Implementation is what was suggested in the
thread https://gcc.gnu.org/ml/gcc/2014-05/msg00213.html.

I have broken this into:

Patch 1 - Changes to store zero and sign extended promotions
(SPR_SIGNED_AND_UNSIGNED) in SUBREG with SUBREG_PROMOTED_VAR_P.
Patch 2 - Enables Zext/sext extensions by checking the value range.

test-cases that motivated this and the asm difference with the patch are:

1.
short foo(unsigned char c)
{
  c = c & (unsigned char)0x0F;
  if( c > 7 )
    return((short)(c - 5));
  else
    return(( short )c);
}

 	and	r0, r0, #15
 	cmp	r0, #7
 	subhi	r0, r0, #5
-	uxth	r0, r0
-	sxth	r0, r0
 	bx	lr

2.
unsigned short
crc2(unsigned short crc, unsigned char data)
{
   unsigned char i, x16, carry;
   for (i = 0; i < 8; i++)
     {
       x16 = (data ^ crc) & 1;
       data >>= 1;
       if (x16 == 1)
         {
           crc ^= 0x4002;
           carry = 1;
         }
       else
         carry = 0;
      crc >>= 1;
       if (carry)
         crc |= 0x8000;
       else
         crc &= 0x7fff;
     }
   return crc;
}

-	mov	r3, #8
+	mov	r2, #8
 .L3:
-	eor	r2, r1, r0
-	sub	r3, r3, #1
-	tst	r2, #1
+	eor	r3, r1, r0
 	mov	r1, r1, lsr #1
+	tst	r3, #1
 	eorne	r0, r0, #16384
 	moveq	r0, r0, lsr #1
 	eorne	r0, r0, #2
 	movne	r0, r0, lsr #1
 	orrne	r0, r0, #32768
-	ands	r3, r3, #255
+	subs	r2, r2, #1
 	bne	.L3
 	bx	lr

Tested both patches on x86_64-unknown-linux-gnu and
arm-none-linux-gnueabi with no new regressions. Is this OK?

Thanks,
Kugan