radeonsi/nir: handle key.mono.u.ps.interpolate_at_sample_force_center

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>

src/amd/common/ac_nir_to_llvm.c

@@ -3080,6 +3080,9 @@ static LLVMValueRef barycentric_at_sample(struct ac_nir_context *ctx,
 					  unsigned mode,
 					  LLVMValueRef sample_id)
 {
+	if (ctx->abi->interp_at_sample_force_center)
+		return barycentric_center(ctx, mode);
+
 	LLVMValueRef halfval = LLVMConstReal(ctx->ac.f32, 0.5f);
 
 	/* fetch sample ID */

src/amd/common/ac_shader_abi.h

@@ -203,6 +203,7 @@ struct ac_shader_abi {
 	/* Whether to clamp the shadow reference value to [0,1]on GFX8. Radeonsi currently
 	 * uses it due to promoting D16 to D32, but radv needs it off. */
 	bool clamp_shadow_reference;
+	bool interp_at_sample_force_center;
 
 	/* Whether to workaround GFX9 ignoring the stride for the buffer size if IDXEN=0
 	* and LLVM optimizes an indexed load with constant index to IDXEN=0. */

src/gallium/drivers/radeonsi/si_shader_nir.c

@@ -1243,6 +1243,9 @@ bool si_nir_build_llvm(struct si_shader_context *ctx, struct nir_shader *nir)
                                 ac_to_integer(&ctx->ac,
                                               ac_build_gather_values(&ctx->ac, values, 4));
                 }
+
+		ctx->abi.interp_at_sample_force_center =
+			ctx->shader->key.mono.u.ps.interpolate_at_sample_force_center;
 	}
 
 	ctx->abi.inputs = &ctx->inputs[0];