Mesa (master): gallivm: fix edge cases in exp2
Zack Rusin
zack at kemper.freedesktop.org
Fri Jul 19 20:34:22 UTC 2013
Module: Mesa
Branch: master
Commit: 7b672c1503abffcc83a30a9731419539f52ac73f
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=7b672c1503abffcc83a30a9731419539f52ac73f
Author: Zack Rusin <zackr at vmware.com>
Date: Thu Jul 18 02:38:54 2013 -0400
gallivm: fix edge cases in exp2
exp(0) has to be exactly 1, exp(-inf) has to be 0, exp(inf) has
to be inf and exp(nan) has to be nan, this fixes all of those
cases.
Signed-off-by: Zack Rusin <zackr at vmware.com>
Reviewed-by: Jose Fonseca <jfonseca at vmware.com>
Reviewed-by: Roland Scheidegger <sroland at vmware.com>
---
src/gallium/auxiliary/gallivm/lp_bld_arit.c | 10 +++++++---
1 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_arit.c b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
index d2d91f5..34e3ed9 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_arit.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
@@ -3141,7 +3141,7 @@ lp_build_polynomial(struct lp_build_context *bld,
*/
const double lp_build_exp2_polynomial[] = {
#if EXP_POLY_DEGREE == 5
- 0.999999925063526176901,
+ 1.000000000000000000000, /*XXX: was 0.999999925063526176901, recompute others */
0.693153073200168932794,
0.240153617044375388211,
0.0558263180532956664775,
@@ -3196,8 +3196,12 @@ lp_build_exp2_approx(struct lp_build_context *bld,
assert(type.floating && type.width == 32);
- x = lp_build_min(bld, x, lp_build_const_vec(bld->gallivm, type, 129.0));
- x = lp_build_max(bld, x, lp_build_const_vec(bld->gallivm, type, -126.99999));
+ /* We want to preserve NaN and make sure than for exp2 if x > 128,
+ * the result is INF and if it's smaller than -126.9 the result is 0 */
+ x = lp_build_min_ext(bld, lp_build_const_vec(bld->gallivm, type, 128.0), x,
+ GALLIVM_NAN_RETURN_SECOND);
+ x = lp_build_max_ext(bld, lp_build_const_vec(bld->gallivm, type, -126.99999), x,
+ GALLIVM_NAN_RETURN_SECOND);
/* ipart = floor(x) */
/* fpart = x - ipart */
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