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RFAdvice - a couple of old lost Altivec patches
- From: Zack Weinberg <zack at codesourcery dot com>
- To: gcc at gcc dot gnu dot org
- Date: Wed, 2 Oct 2002 15:33:38 -0700
- Subject: RFAdvice - a couple of old lost Altivec patches
I've been going through a customer's old 2.95+Altivec tree trying to
bring them up to 3.2. I found a couple of patches that appear not to
have made it into 3.2, but may still be desirable there.
One is very simple: it adds to ppc-asm.h
#define vX X
for X in 0 .. 31. (Near the existing such defines for rX and fX.)
This can be put in easily but I don't know if it's wanted or not.
The other is a bit hairier. The existing easy_vector_constant()
routine in rs6000.c only considers all-bits-zero easy. The patch adds
a whole bunch more bit patterns that are considered easy - I quote the
code below for reference. This is a clearly desirable feature; the
difficulty is, the routine is written to the old layout of
CONST_VECTOR. I'm having trouble figuring out how to update it for
the new one. Anyone have suggestions?
zw
int
easy_vector_constant (op)
register rtx op;
{
unsigned HOST_WIDE_INT immed;
if (GET_CODE (op) != CONST_VECTOR
|| GET_MODE (op) != SVmode)
return 0;
immed = CONST_VECTOR_0 (op);
/* If the four 32-bit words aren't the same, it can't be done unless it
matches an lvsl or lvsr value. */
if (immed != CONST_VECTOR_1 (op)
|| immed != CONST_VECTOR_2 (op)
|| immed != CONST_VECTOR_3 (op))
{
if (immed + 0x04040404 == CONST_VECTOR_1 (op)
&& CONST_VECTOR_1 (op) + 0x04040404 == CONST_VECTOR_2 (op)
&& CONST_VECTOR_2 (op) + 0x04040404 == CONST_VECTOR_3 (op)
&& (immed >> 16) + 0x0202 == (immed & 0xffff)
&& (immed >> 24) + 1 == ((immed >> 16) & 0xff)
&& (immed >>= 24) <= 0x10)
{
if (immed == 0x10)
/* Use lvsr 0,0. */
return 7;
else
/* Use lvsl 0,immed. */
return 8;
}
else
return 0;
}
/* vxor v,v,v and vspltisw v,0 will work. */
else if (immed == 0)
return 1;
/* vcmpequw v,v,v and vspltisw v,-1 will work. */
else if (immed + 1 == 0)
return 2;
/* vsubcuw v,v,v and vspltisw v,1 will work. */
else if (immed == 1)
return 3;
/* vspltisw will work. */
else if (immed + 16 < 32)
return 4;
/* The two 16-bit halves aren't the same. */
else if (immed >> 16 != (immed & 0xffff))
return 0;
/* vspltish will work. */
else if (((immed + 16) & 0xffff) < 32)
return 5;
/* The two 8-bit halves aren't the same. */
else if (immed >> 24 != (immed & 0xff))
return 0;
/* vspltisb will work. */
else if (((immed + 16) & 0xff) < 32)
return 6;
return 0;
}