glsl: lower builtins to mediump that always return mediump or lowp

[mesa.git] / src / compiler / glsl / lower_precision.cpp

diff --git a/src/compiler/glsl/lower_precision.cpp b/src/compiler/glsl/lower_precision.cpp
index e9975322e84f1daa9f923cdfba6eccd98363b341..7fb7257f2ab08a25881fccb5353184d8dcfc7003 100644 (file)
--- a/src/compiler/glsl/lower_precision.cpp
+++ b/src/compiler/glsl/lower_precision.cpp
@@ -408,6 +408,17 @@ find_lowerable_rvalues_visitor::visit_enter(ir_expression *ir)
    return visit_continue;
 }
 
+static bool
+function_always_returns_mediump_or_lowp(const char *name)
+{
+   return !strcmp(name, "bitCount") ||
+          !strcmp(name, "findLSB") ||
+          !strcmp(name, "findMSB") ||
+          !strcmp(name, "unpackHalf2x16") ||
+          !strcmp(name, "unpackUnorm4x8") ||
+          !strcmp(name, "unpackSnorm4x8");
+}
+
 static bool
 is_lowerable_builtin(ir_call *ir,
                      const struct set *lowerable_rvalues)
@@ -499,10 +510,33 @@ is_lowerable_builtin(ir_call *ir,
 
    assert(ir->callee->return_precision == GLSL_PRECISION_NONE);
 
+   /* Number of parameters to check if they are lowerable. */
+   unsigned check_parameters = ir->actual_parameters.length();
+
+   /* Interpolation functions only consider the precision of the interpolant. */
+   /* Bitfield functions ignore the precision of "offset" and "bits". */
+   if (!strcmp(ir->callee_name(), "interpolateAtOffset") ||
+       !strcmp(ir->callee_name(), "interpolateAtSample") ||
+       !strcmp(ir->callee_name(), "bitfieldExtract")) {
+      check_parameters = 1;
+   } else if (!strcmp(ir->callee_name(), "bitfieldInsert")) {
+      check_parameters = 2;
+   } if (function_always_returns_mediump_or_lowp(ir->callee_name())) {
+      /* These only lower the return value. Parameters keep their precision,
+       * which is preserved in map_builtin.
+       */
+      check_parameters = 0;
+   }
+
    foreach_in_list(ir_rvalue, param, &ir->actual_parameters) {
+      if (!check_parameters)
+         break;
+
       if (!param->as_constant() &&
           _mesa_set_search(lowerable_rvalues, param) == NULL)
          return false;
+
+      --check_parameters;
    }
 
    return true;
@@ -857,8 +891,14 @@ find_precision_visitor::map_builtin(ir_function_signature *sig)
    ir_function_signature *lowered_sig =
       sig->clone(lowered_builtin_mem_ctx, clone_ht);
 
-   foreach_in_list(ir_variable, param, &lowered_sig->parameters) {
-      param->data.precision = GLSL_PRECISION_MEDIUM;
+   /* Functions that always return mediump or lowp should keep their
+    * parameters intact, because they can be highp. NIR can lower
+    * the up-conversion for parameters if needed.
+    */
+   if (!function_always_returns_mediump_or_lowp(sig->function_name())) {
+      foreach_in_list(ir_variable, param, &lowered_sig->parameters) {
+         param->data.precision = GLSL_PRECISION_MEDIUM;
+      }
    }
 
    lower_precision(options, &lowered_sig->body);