Cycles: tweaks for better GPU code generation

Uninitialized variables are harder to handle for the compiler.

Ref D5363

intern/cycles/kernel/kernel_emission.h

@@ -27,7 +27,7 @@ ccl_device_noinline float3 direct_emissive_eval(KernelGlobals *kg,
                                                 float time)
 {
   /* setup shading at emitter */
-  float3 eval;
+  float3 eval = make_float3(0.0f, 0.0f, 0.0f);
 
   if (shader_constant_emission_eval(kg, ls->shader, &eval)) {
     if ((ls->prim != PRIM_NONE) && dot(ls->Ng, I) < 0.0f) {
@@ -314,7 +314,7 @@ ccl_device_noinline float3 indirect_background(KernelGlobals *kg,
   }
 
   /* Evaluate background shader. */
-  float3 L;
+  float3 L = make_float3(0.0f, 0.0f, 0.0f);
   if (!shader_constant_emission_eval(kg, shader, &L)) {
 #  ifdef __SPLIT_KERNEL__
     Ray priv_ray = *ray;

intern/cycles/kernel/kernel_path.h

@@ -103,7 +103,7 @@ ccl_device_forceinline void kernel_path_lamp_emission(KernelGlobals *kg,
     light_ray.dP = ray->dP;
 
     /* intersect with lamp */
-    float3 emission;
+    float3 emission = make_float3(0.0f, 0.0f, 0.0f);
 
     if (indirect_lamp_emission(kg, emission_sd, state, &light_ray, &emission))
       path_radiance_accum_emission(L, state, throughput, emission);

intern/cycles/kernel/kernel_shader.h

@@ -778,7 +778,7 @@ ccl_device_inline int shader_bsdf_sample(KernelGlobals *kg,
   kernel_assert(CLOSURE_IS_BSDF(sc->type));
 
   int label;
-  float3 eval;
+  float3 eval = make_float3(0.0f, 0.0f, 0.0f);
 
   *pdf = 0.0f;
   label = bsdf_sample(kg, sd, sc, randu, randv, &eval, omega_in, domega_in, pdf);
@@ -808,7 +808,7 @@ ccl_device int shader_bsdf_sample_closure(KernelGlobals *kg,
   PROFILING_INIT(kg, PROFILING_CLOSURE_SAMPLE);
 
   int label;
-  float3 eval;
+  float3 eval = make_float3(0.0f, 0.0f, 0.0f);
 
   *pdf = 0.0f;
   label = bsdf_sample(kg, sd, sc, randu, randv, &eval, omega_in, domega_in, pdf);
@@ -1221,7 +1221,7 @@ ccl_device int shader_volume_phase_sample(KernelGlobals *kg,
    * depending on color channels, even if this is perhaps not a common case */
   const ShaderClosure *sc = &sd->closure[sampled];
   int label;
-  float3 eval;
+  float3 eval = make_float3(0.0f, 0.0f, 0.0f);
 
   *pdf = 0.0f;
   label = volume_phase_sample(sd, sc, randu, randv, &eval, omega_in, domega_in, pdf);
@@ -1246,7 +1246,7 @@ ccl_device int shader_phase_sample_closure(KernelGlobals *kg,
   PROFILING_INIT(kg, PROFILING_CLOSURE_VOLUME_SAMPLE);
 
   int label;
-  float3 eval;
+  float3 eval = make_float3(0.0f, 0.0f, 0.0f);
 
   *pdf = 0.0f;
   label = volume_phase_sample(sd, sc, randu, randv, &eval, omega_in, domega_in, pdf);

intern/cycles/kernel/kernel_volume.h

@@ -187,7 +187,7 @@ ccl_device void kernel_volume_shadow_homogeneous(KernelGlobals *kg,
                                                  ShaderData *sd,
                                                  float3 *throughput)
 {
-  float3 sigma_t;
+  float3 sigma_t = make_float3(0.0f, 0.0f, 0.0f);
 
   if (volume_shader_extinction_sample(kg, sd, state, ray->P, &sigma_t))
     *throughput *= volume_color_transmittance(sigma_t, ray->t);
@@ -225,7 +225,7 @@ ccl_device void kernel_volume_shadow_heterogeneous(KernelGlobals *kg,
     }
 
     float3 new_P = ray->P + ray->D * (t + step_offset);
-    float3 sigma_t;
+    float3 sigma_t = make_float3(0.0f, 0.0f, 0.0f);
 
     /* compute attenuation over segment */
     if (volume_shader_extinction_sample(kg, sd, state, new_P, &sigma_t)) {
@@ -621,6 +621,7 @@ kernel_volume_integrate_heterogeneous_distance(KernelGlobals *kg,
         new_tp = tp * transmittance;
       }
       else {
+        transmittance = make_float3(0.0f, 0.0f, 0.0f);
         new_tp = tp;
       }
 

intern/cycles/kernel/svm/svm_attribute.h

@@ -46,8 +46,8 @@ ccl_device AttributeDescriptor svm_node_attr_init(
 
 ccl_device void svm_node_attr(KernelGlobals *kg, ShaderData *sd, float *stack, uint4 node)
 {
-  NodeAttributeType type;
-  uint out_offset;
+  NodeAttributeType type = NODE_ATTR_FLOAT;
+  uint out_offset = 0;
   AttributeDescriptor desc = svm_node_attr_init(kg, sd, node, &type, &out_offset);
 
   /* fetch and store attribute */
@@ -88,8 +88,8 @@ ccl_device_noinline
     void
     svm_node_attr_bump_dx(KernelGlobals *kg, ShaderData *sd, float *stack, uint4 node)
 {
-  NodeAttributeType type;
-  uint out_offset;
+  NodeAttributeType type = NODE_ATTR_FLOAT;
+  uint out_offset = 0;
   AttributeDescriptor desc = svm_node_attr_init(kg, sd, node, &type, &out_offset);
 
   /* fetch and store attribute */
@@ -133,8 +133,8 @@ ccl_device_noinline
     void
     svm_node_attr_bump_dy(KernelGlobals *kg, ShaderData *sd, float *stack, uint4 node)
 {
-  NodeAttributeType type;
-  uint out_offset;
+  NodeAttributeType type = NODE_ATTR_FLOAT;
+  uint out_offset = 0;
   AttributeDescriptor desc = svm_node_attr_init(kg, sd, node, &type, &out_offset);
 
   /* fetch and store attribute */

intern/cycles/kernel/svm/svm_bevel.h

@@ -53,7 +53,7 @@ ccl_device_noinline float3 svm_bevel(KernelGlobals *kg,
   float3 sum_N = make_float3(0.0f, 0.0f, 0.0f);
 
   for (int sample = 0; sample < num_samples; sample++) {
-    float disk_u, disk_v;
+    float disk_u = 0.0f, disk_v = 0.0f;
     path_branched_rng_2D(
         kg, state->rng_hash, state, sample, num_samples, PRNG_BEVEL_U, &disk_u, &disk_v);
 

intern/cycles/kernel/svm/svm_brick.h

@@ -18,7 +18,7 @@ CCL_NAMESPACE_BEGIN
 
 /* Brick */
 
-ccl_device_noinline float brick_noise(uint n) /* fast integer noise */
+ccl_device_inline float brick_noise(uint n) /* fast integer noise */
 {
   uint nn;
   n = (n + 1013) & 0x7fffffff;

intern/cycles/kernel/svm/svm_checker.h

@@ -18,7 +18,7 @@ CCL_NAMESPACE_BEGIN
 
 /* Checker */
 
-ccl_device_noinline float svm_checker(float3 p)
+ccl_device float svm_checker(float3 p)
 {
   /* avoid precision issues on unit coordinates */
   p.x = (p.x + 0.000001f) * 0.999999f;