shader: materialize exact buffer capacity through shared clean reads

Co-authored-by: shadowbeat070 <70843316+shadowbeat070@users.noreply.github.com>

src/graphics/shader/recompiler/ir/Program.cpp

@@ -190,6 +190,18 @@ Value ResolveInvariantPhi(const ResourcePlan& program, Value value) {
 	return invariant;
 }
 
+Value ResolveActiveU32(Value value, Value active) {
+	for (uint32_t depth = 0; depth <= 32; ++depth) {
+		value = value.Resolve();
+		const auto* inst = value.TryInstruction();
+		if (inst == nullptr || inst->GetOpcode() != ValueOpcode::SelectU32 ||
+		    inst->Arg(0).Resolve() != active)
+			return value;
+		value = inst->Arg(1);
+	}
+	return {};
+}
+
 bool HasShaderMemoryWrites(const Program& program) {
 	for (const auto* block: program.blocks) {
 		for (const auto& inst: *block) {