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gallivm: Updated lp_build_polynomial to compute odd and even terms separately to decrease data dependency for faster runtime.

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Signed-off-by: José Fonseca <jfonseca@vmware.com>
This commit is contained in:
James Benton 2012-04-05 20:32:51 +01:00 • committed by José Fonseca
parent 129d5138d6
commit 7c639feb2f
1 changed files with 25 additions and 7 deletions
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32
src/gallium/auxiliary/gallivm/lp_bld_arit.c
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@ -2163,7 +2163,8 @@ lp_build_polynomial(struct lp_build_context *bld,
unsigned num_coeffs)
{
const struct lp_type type = bld->type;
LLVMValueRef res = NULL;
LLVMValueRef even = NULL, odd = NULL;
LLVMValueRef x2;
unsigned i;
assert(lp_check_value(bld->type, x));
@ -2175,19 +2176,36 @@ lp_build_polynomial(struct lp_build_context *bld,
__FUNCTION__);
}
/*
* Calculate odd and even terms seperately to decrease data dependency
* Ex:
* c[0] + x^2 * c[2] + x^4 * c[4] ...
* + x * (c[1] + x^2 * c[3] + x^4 * c[5]) ...
*/
x2 = lp_build_mul(bld, x, x);
for (i = num_coeffs; i--; ) {
LLVMValueRef coeff;
coeff = lp_build_const_vec(bld->gallivm, type, coeffs[i]);
if(res)
res = lp_build_add(bld, coeff, lp_build_mul(bld, x, res));
else
res = coeff;
if (i % 2 == 0) {
if (even)
even = lp_build_add(bld, coeff, lp_build_mul(bld, x2, even));
else
even = coeff;
} else {
if (odd)
odd = lp_build_add(bld, coeff, lp_build_mul(bld, x2, odd));
else
odd = coeff;
}
}
if(res)
return res;
if (odd)
return lp_build_add(bld, lp_build_mul(bld, odd, x), even);
else if (even)
return even;
else
return bld->undef;
}