shader_decode: Implement ISET

src/video_core/shader/decode/integer_set.cpp

@@ -16,7 +16,33 @@ u32 ShaderIR::DecodeIntegerSet(BasicBlock& bb, u32 pc) {
     const Instruction instr = {program_code[pc]};
     const auto opcode = OpCode::Decode(instr);
 
-    UNIMPLEMENTED();
+    const Node op_a = GetRegister(instr.gpr8);
+    const Node op_b = [&]() {
+        if (instr.is_b_imm) {
+            return Immediate(instr.alu.GetSignedImm20_20());
+        } else if (instr.is_b_gpr) {
+            return GetRegister(instr.gpr20);
+        } else {
+            return GetConstBuffer(instr.cbuf34.index, instr.cbuf34.offset);
+        }
+    }();
+
+    // The iset instruction sets a register to 1.0 or -1 (depending on the bf bit) if the condition
+    // is true, and to 0 otherwise.
+    const Node second_pred = GetPredicate(instr.iset.pred39, instr.iset.neg_pred != 0);
+    const Node first_pred =
+        GetPredicateComparisonInteger(instr.iset.cond, instr.iset.is_signed, op_a, op_b);
+
+    const OperationCode combiner = GetPredicateCombiner(instr.iset.op);
+
+    const Node predicate = Operation(combiner, first_pred, second_pred);
+
+    const Node true_value = instr.iset.bf ? Immediate(1.0f) : Immediate(-1);
+    const Node false_value = instr.iset.bf ? Immediate(0.0f) : Immediate(0);
+    const Node value =
+        Operation(OperationCode::Select, PRECISE, predicate, true_value, false_value);
+
+    SetRegister(bb, instr.gpr0, value);
 
     return pc;
 }