zig

commit 199782edd16ca1fe08cee57ee2219c0a0c385fdc (tree)
parent bf21e4f72528e0cf5bfcbc95172f641b9d5b53e8
Author: Alex Rønne Petersen <alex@alexrp.com>
Date:   Sat,  2 Nov 2024 08:59:14 +0100

riscv64: Handle writes to the zero register sensibly in result bookkeeping.

Diffstat:
M
src/arch/riscv64/CodeGen.zig
 | 
9
++++++++-

1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/src/arch/riscv64/CodeGen.zig b/src/arch/riscv64/CodeGen.zig
@@ -1768,8 +1768,15 @@ fn finishAirBookkeeping(func: *Func) void {
 fn finishAirResult(func: *Func, inst: Air.Inst.Index, result: MCValue) void {
     if (func.liveness.isUnused(inst)) switch (result) {
         .none, .dead, .unreach => {},
-        else => unreachable, // Why didn't the result die?
+        // Why didn't the result die?
+        .register => |r| if (r != .zero) unreachable,
+        else => unreachable,
     } else {
+        switch (result) {
+            .register => |r| if (r == .zero) unreachable, // Why did we discard a used result?
+            else => {},
+        }
+
         tracking_log.debug("%{d} => {} (birth)", .{ inst, result });
         func.inst_tracking.putAssumeCapacityNoClobber(inst, InstTracking.init(result));
         // In some cases, an operand may be reused as the result.