patch

0001-gallivm-Use-nextafterf-0.5-0.0-as-rounding-constant.patch (text/plain), 1.20 KB, created by Matt Turner on 2018-11-21 20:18:14 UTC

From e88bef7b7d7e523ddeedd133a0860b935efb65db Mon Sep 17 00:00:00 2001
From: Matt Turner <[e-mail]>
Date: Wed, 21 Nov 2018 12:13:19 -0800
Subject: [PATCH] gallivm: Use nextafterf(0.5, 0.0) as rounding constant

The common truncf(x + 0.5) fails for the floating-point value just less
than 0.5 (nextafterf(0.5, 0.0)) for x=0.5. nextafterf(0.5, 0.0) + 0.5,
after rounding is 1.0, thus truncf does not produce the desired value.

The solution is to add nextafterf(0.5, 0.0). This works for all values.

Distro-bug: https://bugs.gentoo.org/665570
---
 src/gallium/auxiliary/gallivm/lp_bld_arit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/gallium/auxiliary/gallivm/lp_bld_arit.c b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
index f348833206b..c050bfdb936 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_arit.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
@@ -2477,7 +2477,7 @@ lp_build_iround(struct lp_build_context *bld,
    else {
       LLVMValueRef half;
 
-      half = lp_build_const_vec(bld->gallivm, type, 0.5);
+      half = lp_build_const_vec(bld->gallivm, type, nextafterf(0.5, 0.0));
 
       if (type.sign) {
          LLVMTypeRef vec_type = bld->vec_type;
-- 
2.18.1