From 3cf9ae6ff30f2648b6233ede61ad0d1e75a30d14 Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Fri, 10 Dec 2021 13:05:06 +0530
Subject: [PATCH 1/3] inline slice panics on panic_immediate_abort

---
 library/core/src/slice/index.rs | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/library/core/src/slice/index.rs b/library/core/src/slice/index.rs
index f7224303549..0298bba8d32 100644
--- a/library/core/src/slice/index.rs
+++ b/library/core/src/slice/index.rs
@@ -27,35 +27,40 @@ fn index_mut(&mut self, index: I) -> &mut I::Output {
     }
 }
 
-#[inline(never)]
+#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+#[cfg_attr(feature = "panic_immediate_abort", inline)]
 #[cold]
 #[track_caller]
 fn slice_start_index_len_fail(index: usize, len: usize) -> ! {
     panic!("range start index {} out of range for slice of length {}", index, len);
 }
 
-#[inline(never)]
+#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+#[cfg_attr(feature = "panic_immediate_abort", inline)]
 #[cold]
 #[track_caller]
 fn slice_end_index_len_fail(index: usize, len: usize) -> ! {
     panic!("range end index {} out of range for slice of length {}", index, len);
 }
 
-#[inline(never)]
+#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+#[cfg_attr(feature = "panic_immediate_abort", inline)]
 #[cold]
 #[track_caller]
 fn slice_index_order_fail(index: usize, end: usize) -> ! {
     panic!("slice index starts at {} but ends at {}", index, end);
 }
 
-#[inline(never)]
+#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+#[cfg_attr(feature = "panic_immediate_abort", inline)]
 #[cold]
 #[track_caller]
 fn slice_start_index_overflow_fail() -> ! {
     panic!("attempted to index slice from after maximum usize");
 }
 
-#[inline(never)]
+#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+#[cfg_attr(feature = "panic_immediate_abort", inline)]
 #[cold]
 #[track_caller]
 fn slice_end_index_overflow_fail() -> ! {

From 0adee2c01eb5ecb91df3b4ac1c045b18f8a4c2f5 Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Fri, 10 Dec 2021 13:08:06 +0530
Subject: [PATCH 2/3] inline Option panics on panic_immediate_abort

---
 library/core/src/option.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index 7b9c6e43960..aae3af81a52 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -1656,7 +1656,8 @@ pub const fn transpose(self) -> Result<Option<T>, E> {
 }
 
 // This is a separate function to reduce the code size of .expect() itself.
-#[inline(never)]
+#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+#[cfg_attr(feature = "panic_immediate_abort", inline)]
 #[cold]
 #[track_caller]
 const fn expect_failed(msg: &str) -> ! {

From 917dafc73a9eb257b9b5c2d357c4abd8bb1c3a8e Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Fri, 10 Dec 2021 13:12:26 +0530
Subject: [PATCH 3/3] Add separate impl of unwrap_failed to avoid constructing
 trait objects

---
 library/core/src/result.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/library/core/src/result.rs b/library/core/src/result.rs
index e6b8c8ec338..ab067d57d08 100644
--- a/library/core/src/result.rs
+++ b/library/core/src/result.rs
@@ -1653,6 +1653,7 @@ pub const fn into_ok_or_err(self) -> T {
 }
 
 // This is a separate function to reduce the code size of the methods
+#[cfg(not(feature = "panic_immediate_abort"))]
 #[inline(never)]
 #[cold]
 #[track_caller]
@@ -1660,6 +1661,18 @@ fn unwrap_failed(msg: &str, error: &dyn fmt::Debug) -> ! {
     panic!("{}: {:?}", msg, error)
 }
 
+// This is a separate function to avoid constructing a `dyn Debug`
+// that gets immediately thrown away, since vtables don't get cleaned up
+// by dead code elimination if a trait object is constructed even if it goes
+// unused
+#[cfg(feature = "panic_immediate_abort")]
+#[inline]
+#[cold]
+#[track_caller]
+fn unwrap_failed<T>(_msg: &str, _error: &T) -> ! {
+    panic!()
+}
+
 /////////////////////////////////////////////////////////////////////////////
 // Trait implementations
 /////////////////////////////////////////////////////////////////////////////