From 4aae0b09cfdc444a0b4e98d3ed7f83bfe421c06f Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Sat, 3 Dec 2022 19:30:08 -0700
Subject: CBE and LLVM: handle unused try instructions

In both backends they did not observe the Liveness information for try
instructions. Now they do. For the C backend this is necessary for
correctness; for the LLVM backend, it improves code generation.
---
 src/codegen/c.zig | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'src/codegen/c.zig')

diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index 372e89bac7..ac22ac3fa6 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -4092,9 +4092,14 @@ fn lowerTry(
         }
     }
 
+    try reap(f, inst, &.{operand});
+
+    if (f.liveness.isUnused(inst)) {
+        return CValue.none;
+    }
+
     const target = f.object.dg.module.getTarget();
     const is_array = lowersToArray(payload_ty, target);
-    try reap(f, inst, &.{operand});
     const local = try f.allocLocal(inst, result_ty);
     if (is_array) {
         try writer.writeAll("memcpy(");
-- 
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