From ff4596ae616fccfe9cfb1c1dd995464c5c7eefab Mon Sep 17 00:00:00 2001
From: Georg Lehmann <dadschoorse@gmail.com>
Date: Thu, 12 Sep 2024 09:04:13 +0200
Subject: [PATCH] spirv: explicitly lower derivatives to zero
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To allow removal of the existing nir_builder lowering.

Acked-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31137>
---
 src/compiler/spirv/vtn_alu.c | 68 +++++++++++++++++++++++-------------
 1 file changed, 44 insertions(+), 24 deletions(-)

diff --git a/src/compiler/spirv/vtn_alu.c b/src/compiler/spirv/vtn_alu.c
index fa8135e749c..94c41c710ca 100644
--- a/src/compiler/spirv/vtn_alu.c
+++ b/src/compiler/spirv/vtn_alu.c
@@ -617,6 +617,49 @@ vtn_mediump_upconvert_value(struct vtn_builder *b, struct vtn_ssa_value *value)
    }
 }
 
+static nir_def *
+vtn_handle_deriv(struct vtn_builder *b, SpvOp opcode, nir_def *src)
+{
+   /* SPV_NV_compute_shader_derivatives:
+    * In the GLCompute Execution Model:
+    * Selection of the four invocations is determined by the DerivativeGroup*NV
+    * execution mode that was specified for the entry point.
+    * If neither derivative group mode was specified, the derivatives return zero.
+    */
+   if (b->nb.shader->info.stage == MESA_SHADER_COMPUTE &&
+       b->nb.shader->info.derivative_group == DERIVATIVE_GROUP_NONE) {
+      return nir_imm_zero(&b->nb, src->num_components, src->bit_size);
+   }
+
+   switch (opcode) {
+   case SpvOpDPdx:
+      return nir_ddx(&b->nb, src);
+   case SpvOpDPdxFine:
+      return nir_ddx_fine(&b->nb, src);
+   case SpvOpDPdxCoarse:
+      return nir_ddx_coarse(&b->nb, src);
+   case SpvOpDPdy:
+      return nir_ddy(&b->nb, src);
+   case SpvOpDPdyFine:
+      return nir_ddy_fine(&b->nb, src);
+   case SpvOpDPdyCoarse:
+      return nir_ddy_coarse(&b->nb, src);
+   case SpvOpFwidth:
+      return nir_fadd(&b->nb,
+                      nir_fabs(&b->nb, nir_ddx(&b->nb, src)),
+                      nir_fabs(&b->nb, nir_ddy(&b->nb, src)));
+   case SpvOpFwidthFine:
+      return nir_fadd(&b->nb,
+                      nir_fabs(&b->nb, nir_ddx_fine(&b->nb, src)),
+                      nir_fabs(&b->nb, nir_ddy_fine(&b->nb, src)));
+   case SpvOpFwidthCoarse:
+      return nir_fadd(&b->nb,
+                      nir_fabs(&b->nb, nir_ddx_coarse(&b->nb, src)),
+                      nir_fabs(&b->nb, nir_ddy_coarse(&b->nb, src)));
+   default: unreachable("Not a derivative opcode");
+   }
+}
+
 void
 vtn_handle_alu(struct vtn_builder *b, SpvOp opcode,
                const uint32_t *w, unsigned count)
@@ -721,38 +764,15 @@ vtn_handle_alu(struct vtn_builder *b, SpvOp opcode,
    }
 
    case SpvOpDPdx:
-      dest->def = nir_ddx(&b->nb, src[0]);
-      break;
    case SpvOpDPdxFine:
-      dest->def = nir_ddx_fine(&b->nb, src[0]);
-      break;
    case SpvOpDPdxCoarse:
-      dest->def = nir_ddx_coarse(&b->nb, src[0]);
-      break;
    case SpvOpDPdy:
-      dest->def = nir_ddy(&b->nb, src[0]);
-      break;
    case SpvOpDPdyFine:
-      dest->def = nir_ddy_fine(&b->nb, src[0]);
-      break;
    case SpvOpDPdyCoarse:
-      dest->def = nir_ddy_coarse(&b->nb, src[0]);
-      break;
-
    case SpvOpFwidth:
-      dest->def = nir_fadd(&b->nb,
-                               nir_fabs(&b->nb, nir_ddx(&b->nb, src[0])),
-                               nir_fabs(&b->nb, nir_ddy(&b->nb, src[0])));
-      break;
    case SpvOpFwidthFine:
-      dest->def = nir_fadd(&b->nb,
-                               nir_fabs(&b->nb, nir_ddx_fine(&b->nb, src[0])),
-                               nir_fabs(&b->nb, nir_ddy_fine(&b->nb, src[0])));
-      break;
    case SpvOpFwidthCoarse:
-      dest->def = nir_fadd(&b->nb,
-                               nir_fabs(&b->nb, nir_ddx_coarse(&b->nb, src[0])),
-                               nir_fabs(&b->nb, nir_ddy_coarse(&b->nb, src[0])));
+      dest->def = vtn_handle_deriv(b, opcode, src[0]);
       break;
 
    case SpvOpVectorTimesScalar: