From d51a83d26565b58960bb526215d7b300d7b6675e Mon Sep 17 00:00:00 2001
From: MerryMage <MerryMage@users.noreply.github.com>
Date: Wed, 22 Apr 2020 00:20:38 +0100
Subject: [PATCH] constant_propagation_pass: Fold IsZero

---
 src/ir_opt/constant_propagation_pass.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/ir_opt/constant_propagation_pass.cpp b/src/ir_opt/constant_propagation_pass.cpp
index cf7592cc..02e8b104 100644
--- a/src/ir_opt/constant_propagation_pass.cpp
+++ b/src/ir_opt/constant_propagation_pass.cpp
@@ -337,6 +337,16 @@ void ConstantPropagation(IR::Block& block) {
         case Op::MostSignificantBit:
             FoldMostSignificantBit(inst);
             break;
+        case Op::IsZero32:
+            if (inst.AreAllArgsImmediates()) {
+                inst.ReplaceUsesWith(IR::Value{inst.GetArg(0).GetU32() == 0});
+            }
+            break;
+        case Op::IsZero64:
+            if (inst.AreAllArgsImmediates()) {
+                inst.ReplaceUsesWith(IR::Value{inst.GetArg(0).GetU64() == 0});
+            }
+            break;
         case Op::LogicalShiftLeft32:
             if (FoldShifts(inst)) {
                 ReplaceUsesWith(inst, true, Safe::LogicalShiftLeft<u32>(inst.GetArg(0).GetU32(), inst.GetArg(1).GetU8()));