Mesa (master): aco: disable omod if the sign of zeros should be preserved

[GitLab Mirror]

Module: Mesa
Branch: master
Commit: 558daa73f9adb1275ddcf00515c7f79f726b7ae1
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=558daa73f9adb1275ddcf00515c7f79f726b7ae1

Author: Rhys Perry <pendingchaos02 at gmail.com>
Date:   Fri Nov 13 15:10:58 2020 +0000

aco: disable omod if the sign of zeros should be preserved

The RDNA ISA doc says that omod doesn't preserve -0.0 in 6.2.2. LLVM
appears to always disable omod in this situation, but clamp is unaffected.

Signed-off-by: Rhys Perry <pendingchaos02 at gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
Fixes: df645fa369d ("aco: implement VK_KHR_shader_float_controls")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7605>

---

 src/amd/compiler/aco_optimizer.cpp | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/amd/compiler/aco_optimizer.cpp b/src/amd/compiler/aco_optimizer.cpp
index 01dcafdcb44..62567941541 100644
--- a/src/amd/compiler/aco_optimizer.cpp
+++ b/src/amd/compiler/aco_optimizer.cpp
@@ -2606,9 +2606,14 @@ bool apply_omod_clamp(opt_ctx &ctx, Block& block, aco_ptr<Instruction>& instr)
    if (!instr->isSDWA() && !can_vop3)
       return false;
 
-   /* omod has no effect if denormals are enabled */
-   bool can_use_omod = (instr->definitions[0].bytes() == 4 ? block.fp_mode.denorm32 : block.fp_mode.denorm16_64) == 0;
-   can_use_omod = can_use_omod && (can_vop3 || ctx.program->chip_class >= GFX9); /* SDWA omod is GFX9+ */
+   /* omod flushes -0 to +0 and has no effect if denormals are enabled */
+   bool can_use_omod = (can_vop3 || ctx.program->chip_class >= GFX9); /* SDWA omod is GFX9+ */
+   if (instr->definitions[0].bytes() == 4)
+      can_use_omod = can_use_omod && block.fp_mode.denorm32 == 0 &&
+                     !block.fp_mode.preserve_signed_zero_inf_nan32;
+   else
+      can_use_omod = can_use_omod && block.fp_mode.denorm16_64 == 0 &&
+                     !block.fp_mode.preserve_signed_zero_inf_nan16_64;
 
    ssa_info& def_info = ctx.info[instr->definitions[0].tempId()];