From a6172f19a0915fc690104a02e894b263d982e247 Mon Sep 17 00:00:00 2001
From: Karol Herbst <kherbst@redhat.com>
Date: Thu, 21 May 2026 14:17:52 +0200
Subject: [PATCH] vtn/opencl: fix edge case behavior for tanpi

Cc: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41726>
---
 src/compiler/spirv/vtn_opencl.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/compiler/spirv/vtn_opencl.c b/src/compiler/spirv/vtn_opencl.c
index c341910f56f..2d2a6e29a20 100644
--- a/src/compiler/spirv/vtn_opencl.c
+++ b/src/compiler/spirv/vtn_opencl.c
@@ -726,6 +726,21 @@ handle_special(struct vtn_builder *b, uint32_t opcode,
       break;
    }
 
+   case OpenCLstd_Tanpi: {
+      if (nb->fp_math_ctrl & nir_fp_preserve_signed_zero) {
+         nir_def *remainder = nir_fmod(nb, nir_fabs(nb, srcs[0]), nir_imm_floatN_t(nb, 2.0, ret->bit_size));
+         nir_def *is_odd = nir_feq_imm(nb, remainder, 1.0);
+         nir_def *is_even = nir_feq_imm(nb, remainder, 0.0);
+
+         /* tanpi(n) is copysign(0.0, - n) for odd integers n. */
+         ret = nir_bcsel(nb, is_odd, nir_copysign(nb, ret, nir_fneg(nb, srcs[0])), ret);
+
+         /* tanpi(n) is copysign(0.0, n) for even integers n. */
+         ret = nir_bcsel(nb, is_even, nir_copysign(nb, ret, srcs[0]), ret);
+      }
+      break;
+   }
+
    default:
       break;
    }