Codegen const panic messages as function calls

This skips emitting extra arguments at every callsite (of which there
can be many). For a librustc_driver build with overflow checks enabled,
this cuts 0.7MB from the resulting binary.

Author: Mark-Simulacrum

example/mini_core.rs

@@ -418,6 +418,36 @@ pub fn panic(_msg: &'static str) -> ! {
     }
 }
 
+macro_rules! panic_const {
+    ($($lang:ident = $message:expr,)+) => {
+        #[cfg(not(bootstrap))]
+        pub mod panic_const {
+            use super::*;
+
+            $(
+                #[track_caller]
+                #[lang = stringify!($lang)]
+                pub fn $lang() -> ! {
+                    panic($message);
+                }
+            )+
+        }
+    }
+}
+
+panic_const! {
+    panic_const_add_overflow = "attempt to add with overflow",
+    panic_const_sub_overflow = "attempt to subtract with overflow",
+    panic_const_mul_overflow = "attempt to multiply with overflow",
+    panic_const_div_overflow = "attempt to divide with overflow",
+    panic_const_rem_overflow = "attempt to calculate the remainder with overflow",
+    panic_const_neg_overflow = "attempt to negate with overflow",
+    panic_const_shr_overflow = "attempt to shift right with overflow",
+    panic_const_shl_overflow = "attempt to shift left with overflow",
+    panic_const_div_by_zero = "attempt to divide by zero",
+    panic_const_rem_by_zero = "attempt to calculate the remainder with a divisor of zero",
+}
+
 #[lang = "panic_cannot_unwind"]
 fn panic_cannot_unwind() -> ! {
     unsafe {