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tint: Fix edge for CallSiteRequiredToBeUniform 

If the CallSiteRequiredToBeUniform tag is present, add the edge from
RequiredToBeUniform to a new diagnostic node for the function call,
instead of to the control flow coming out of the function call. Doing
the latter causes a false positive when a function both requires
uniform control flow and causes non-uniform control flow.

Bug: tint:880
Change-Id: Icade8f76302e8c21529502f5f945f1981acfc45a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/90582
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Auto-Submit: James Price <jrprice@google.com>
This commit is contained in:
James Price 2022-05-17 08:08:44 +00:00 committed by Dawn LUCI CQ
parent fac5e39c29
commit 5880ed164a
2 changed files with 30 additions and 5 deletions
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12
src/tint/resolver/uniformity.cc
View File

@ -1150,6 +1150,11 @@ class UniformityGraph {
args.push_back(arg_node);
}
// Note: This is an additional node that isn't described in the specification, for the
// purpose of providing diagnostic information.
Node* call_node = CreateNode(name + "_call", call);
call_node->AddEdge(cf_last_arg);
Node* result = CreateNode(name + "_return_value", call);
result->type = Node::kFunctionCallReturnValue;
Node* cf_after = CreateNode("CF_after_" + name, call);
@ -1199,12 +1204,9 @@ class UniformityGraph {
});
if (callsite_tag == CallSiteRequiredToBeUniform) {
// Note: This deviates from the rules in the specification, which would add the edge
// directly to the incoming CF node. Going through CF_after instead makes it easier to
// produce diagnostics that can identify the function being called.
current_function_->required_to_be_uniform->AddEdge(cf_after);
current_function_->required_to_be_uniform->AddEdge(call_node);
}
cf_after->AddEdge(cf_last_arg);
cf_after->AddEdge(call_node);
if (function_tag == SubsequentControlFlowMayBeNonUniform) {
cf_after->AddEdge(current_function_->may_be_non_uniform);

23
src/tint/resolver/uniformity_test.cc
View File

@ -5584,6 +5584,29 @@ test:7:12 note: reading from read_write storage buffer 'rw' may result in a non-
/// Miscellaneous statement and expression tests.
////////////////////////////////////////////////////////////////////////////////
TEST_F(UniformityAnalysisTest, FunctionRequiresUniformFlowAndCausesNonUniformFlow) {
// Test that a function that requires uniform flow and then causes non-uniform flow can be
// called without error.
std::string src = R"(
@group(0) @binding(0) var<storage, read_write> non_uniform_global : i32;
fn foo() {
_ = dpdx(0.5);
if (non_uniform_global == 0) {
discard;
}
}
@stage(fragment)
fn main() {
foo();
}
)";
RunTest(src, true);
}
TEST_F(UniformityAnalysisTest, TypeConstructor) {
std::string src = R"(
@group(0) @binding(0) var<storage, read_write> non_uniform_global : i32;