tint/hlsl: for default-only switch, only emit condition if it has side-effects
This fixes edge-cases, like the condition expression being a type-cast,
which DXC apparently sees as a variable re-declaration. Example:
fn foo(x : f32) {
switch (i32(x)) {
default {
}
}
}
was emitted as HLSL:
void foo(float x) {
int(x);
do {
} while (false);
}
The `int(x)` is seen as a re-declaration of `x` by DXC.
We fix this by only emitted the condition expression if it has
side-effects (which currently means it contains a call expression).
Bug: tint:1820
Change-Id: I7e4320fa09ea2d634c9e324cb0b752b0ee7dcde9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/118161
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
diff --git a/src/tint/writer/hlsl/generator_impl.cc b/src/tint/writer/hlsl/generator_impl.cc
index bde9d70..d49bcc9 100644
--- a/src/tint/writer/hlsl/generator_impl.cc
+++ b/src/tint/writer/hlsl/generator_impl.cc
@@ -3859,10 +3859,9 @@
// default case body. We work around this here by emitting the default case
// without the switch.
- // Emit the switch condition as-is in case it has side-effects (e.g.
- // function call). Note that's it's fine not to assign the result of the
- // expression.
- {
+ // Emit the switch condition as-is if it has side-effects (e.g.
+ // function call). Note that we can ignore the result of the expression (if any).
+ if (auto* sem_cond = builder_.Sem().Get(stmt->condition); sem_cond->HasSideEffects()) {
auto out = line();
if (!EmitExpression(out, stmt->condition)) {
return false;
