tint: Fix uniformity ICE during error reporting wrt non-uniform pointer parameters

Added support for reporting when pointer parameters point to non-uniform
values. Also add support for binary expressions results that may be
non-uniform.

Bug: chromium:1374534
Change-Id: Ia51557e3a984c69a39f2878c964bf07085599809
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/106560
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>

src/tint/resolver/uniformity.cc

@@ -831,7 +831,7 @@ class UniformityGraph {
                 // Create input nodes for any variables declared before this loop.
                 for (auto* v : current_function_->local_var_decls) {
                     auto name = builder_->Symbols().NameFor(v->Declaration()->symbol);
-                    auto* in_node = CreateNode(name + "_value_loop_in");
+                    auto* in_node = CreateNode(name + "_value_loop_in", v->Declaration());
                     in_node->AddEdge(current_function_->variables.Get(v));
                     info.var_in_nodes[v] = in_node;
                     current_function_->variables.Set(v, in_node);
@@ -1111,7 +1111,7 @@ class UniformityGraph {
                 } else {
                     auto [cf1, v1] = ProcessExpression(cf, b->lhs);
                     auto [cf2, v2] = ProcessExpression(cf1, b->rhs);
-                    auto* result = CreateNode("binary_expr_result");
+                    auto* result = CreateNode("binary_expr_result", b);
                     result->AddEdge(v1);
                     result->AddEdge(v2);
                     return std::pair<Node*, Node*>(cf2, result);
@@ -1527,40 +1527,49 @@ class UniformityGraph {
             // the actual cause of divergence.
         }
 
-        // Show the source of the non-uniform value.
+        auto get_var_type = [&](const sem::Variable* var) {
-        Switch(
-            non_uniform_source->ast,
-            [&](const ast::IdentifierExpression* ident) {
-                std::string var_type = "";
-                auto* var = sem_.Get<sem::VariableUser>(ident)->Variable();
             switch (var->AddressSpace()) {
                 case ast::AddressSpace::kStorage:
-                        var_type = "read_write storage buffer ";
+                    return "read_write storage buffer ";
-                        break;
                 case ast::AddressSpace::kWorkgroup:
-                        var_type = "workgroup storage variable ";
+                    return "workgroup storage variable ";
-                        break;
                 case ast::AddressSpace::kPrivate:
-                        var_type = "module-scope private variable ";
+                    return "module-scope private variable ";
-                        break;
                 default:
-                        if (ast::HasAttribute<ast::BuiltinAttribute>(
+                    if (ast::HasAttribute<ast::BuiltinAttribute>(var->Declaration()->attributes)) {
-                                var->Declaration()->attributes)) {
+                        return "builtin ";
-                            var_type = "builtin ";
                     } else if (ast::HasAttribute<ast::LocationAttribute>(
                                    var->Declaration()->attributes)) {
-                            var_type = "user-defined input ";
+                        return "user-defined input ";
                     } else {
                         // TODO(jrprice): Provide more info for this case.
                     }
                     break;
             }
+            return "";
+        };
+
+        // Show the source of the non-uniform value.
+        Switch(
+            non_uniform_source->ast,
+            [&](const ast::IdentifierExpression* ident) {
+                auto* var = sem_.Get<sem::VariableUser>(ident)->Variable();
+                std::string var_type = get_var_type(var);
                 diagnostics_.add_note(diag::System::Resolver,
                                       "reading from " + var_type + "'" +
                                           builder_->Symbols().NameFor(ident->symbol) +
                                           "' may result in a non-uniform value",
                                       ident->source);
             },
+            [&](const ast::Variable* v) {
+                auto* var = sem_.Get(v);
+                std::string var_type = get_var_type(var);
+                diagnostics_.add_note(diag::System::Resolver,
+                                      "reading from " + var_type + "'" +
+                                          builder_->Symbols().NameFor(v->symbol) +
+                                          "' may result in a non-uniform value",
+                                      v->source);
+            },
             [&](const ast::CallExpression* c) {
                 auto target_name = builder_->Symbols().NameFor(
                     c->target.name->As<ast::IdentifierExpression>()->symbol);
@@ -1600,6 +1609,10 @@ class UniformityGraph {
                     }
                 }
             },
+            [&](const ast::Expression* e) {
+                diagnostics_.add_note(diag::System::Resolver,
+                                      "result of expression may be non-uniform", e->source);
+            },
             [&](Default) {
                 TINT_ICE(Resolver, diagnostics_) << "unhandled source of non-uniformity";
             });

src/tint/resolver/uniformity_test.cc

@@ -7962,6 +7962,99 @@ test:13:7 note: reading from read_write storage buffer 'non_uniform_value' may r
 )");
 }
 
+TEST_F(UniformityAnalysisTest,
+       Error_ParameterRequiredToBeUniformForSubsequentControlFlow_ViaPointer) {
+    // Make sure we correctly identify the function call as the source of non-uniform control flow
+    // and not the if statement with the uniform condition.
+    std::string src = R"(
+@group(0) @binding(1) var<storage, read_write> non_uniform_value : vec4<f32>;
+
+fn foo(limit : ptr<function, f32>) -> f32 {
+  var i : i32;
+  if (f32(i) > *limit) {
+      return 0.0;
+  }
+  return 1.0f;
+}
+
+fn main() {
+  var param : f32 = non_uniform_value.y;
+  let i = foo(&param);
+  let y = dpdx(vec3<f32>());
+}
+)";
+
+    RunTest(src, false);
+    EXPECT_EQ(error_,
+              R"(test:15:11 error: 'dpdx' must only be called from uniform control flow
+  let y = dpdx(vec3<f32>());
+          ^^^^
+
+test:14:15 note: non-uniform function call argument causes subsequent control flow to be non-uniform
+  let i = foo(&param);
+              ^
+
+test:6:3 note: control flow depends on non-uniform value
+  if (f32(i) > *limit) {
+  ^^
+
+test:6:14 note: result of expression may be non-uniform
+  if (f32(i) > *limit) {
+             ^
+
+test:13:21 note: reading from read_write storage buffer 'non_uniform_value' may result in a non-uniform value
+  var param : f32 = non_uniform_value.y;
+                    ^^^^^^^^^^^^^^^^^
+)");
+}
+
+TEST_F(UniformityAnalysisTest,
+       Error_ParameterRequiredToBeUniformForSubsequentControlFlow_ViaPointer_InLoop) {
+    // Make sure we correctly identify the function call as the source of non-uniform control flow
+    // and not the if statement with the uniform condition.
+    std::string src = R"(
+@group(0) @binding(1) var<storage, read_write> non_uniform_value : vec4<f32>;
+
+fn foo(limit : ptr<function, f32>) -> f32 {
+  var i : i32;
+  loop {
+    if (f32(i) > *limit) {
+      return 0.0;
+    }
+  }
+}
+
+fn main() {
+  var param : f32 = non_uniform_value.y;
+  let i = foo(&param);
+  let y = dpdx(vec3<f32>());
+}
+)";
+
+    RunTest(src, false);
+    EXPECT_EQ(error_,
+              R"(test:16:11 error: 'dpdx' must only be called from uniform control flow
+  let y = dpdx(vec3<f32>());
+          ^^^^
+
+test:15:15 note: non-uniform function call argument causes subsequent control flow to be non-uniform
+  let i = foo(&param);
+              ^
+
+test:7:5 note: control flow depends on non-uniform value
+    if (f32(i) > *limit) {
+    ^^
+
+test:4:8 note: reading from 'limit' may result in a non-uniform value
+fn foo(limit : ptr<function, f32>) -> f32 {
+       ^^^^^
+
+test:14:21 note: reading from read_write storage buffer 'non_uniform_value' may result in a non-uniform value
+  var param : f32 = non_uniform_value.y;
+                    ^^^^^^^^^^^^^^^^^
+)");
+}
+
 TEST_F(UniformityAnalysisTest, Error_ShortCircuitingExprCausesNonUniformControlFlow) {
     // Make sure we correctly identify the short-circuit as the source of non-uniform control flow
     // and not the if statement with the uniform condition.