From bfd7592c10befe0ba086f15bf169ab85a311a75e Mon Sep 17 00:00:00 2001
From: Nathan Lee <me@nwlee.tech>
Date: Mon, 24 Aug 2026 20:23:16 -0500
Subject: add floating point error CSR

---
 src/core.rs | 8 ++++++--
 src/main.rs | 3 ++-
 2 files changed, 8 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/core.rs b/src/core.rs
index 2746d1b..24c6a8f 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -388,8 +388,12 @@ pub fn fdiv_s(state: &mut CpuState, rd: usize, rs1: usize, rs2: usize) {
     let b = state.f_registers[rs2];
 
     state.f_registers[rd] = if b == 0.0 {
-        f32::NAN
-        // todo: raise division by zero in csr
+        state.csr[0x001 /*fflags*/] |= 0b100;
+        if a.is_sign_positive() {
+            f32::INFINITY
+        } else {
+            f32::NEG_INFINITY
+        }
     } else {
         a / b
     }
diff --git a/src/main.rs b/src/main.rs
index 74515b1..814dfeb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -420,7 +420,8 @@ fn return_to_userspace(state: &mut CpuState) {
 }
 
 fn exit(state: &mut CpuState) {
-    let data = read_all(&state.memory, RINGBUF_ADDR as u32, RINGBUF_SIZE as u32);
+    let mut data = read_all(&state.memory, RINGBUF_ADDR as u32, RINGBUF_SIZE as u32);
+    data.retain(|&x| x != 0);
     std::fs::write("core_dump.txt", data).unwrap();
     std::process::exit(0);
 }
-- 
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