Auto merge of #122671 - Mark-Simulacrum:const-panic-msg, r=Nilstrieb

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 shared library (see [perf]).

A sample improvement from nightly:

```
        leaq    str.0(%rip), %rdi
        leaq    .Lalloc_d6aeb8e2aa19de39a7f0e861c998af13(%rip), %rdx
        movl    $25, %esi
        callq   *_ZN4core9panicking5panic17h17cabb89c5bcc999E@GOTPCREL(%rip)
```

to this PR:

```
        leaq    .Lalloc_d6aeb8e2aa19de39a7f0e861c998af13(%rip), %rdi
        callq   *_RNvNtNtCsduqIKoij8JB_4core9panicking11panic_const23panic_const_div_by_zero@GOTPCREL(%rip)
```

[perf]: https://perf.rust-lang.org/compare.html?start=a7e4de13c1785819f4d61da41f6704ed69d5f203&end=64fbb4f0b2d621ff46d559d1e9f5ad89a8d7789b&stat=instructions:u

tests/codegen-units/item-collection/implicit-panic-call.rs

@@ -16,10 +16,17 @@ struct Location<'a> {
     _col: u32,
 }
 
-#[lang = "panic"]
+#[lang = "panic_const_div_by_zero"]
 #[inline]
 #[track_caller]
-fn panic(_: &'static str) -> ! {
+fn panic_div_zero() -> ! {
+    loop {}
+}
+
+#[lang = "panic_const_div_overflow"]
+#[inline]
+#[track_caller]
+fn panic_div_overflow() -> ! {
     loop {}
 }
 
@@ -55,4 +62,5 @@ pub fn foo() {
 
 //~ MONO_ITEM fn foo
 //~ MONO_ITEM fn <i32 as Div>::div
-//~ MONO_ITEM fn panic
+//~ MONO_ITEM fn panic_div_zero
+//~ MONO_ITEM fn panic_div_overflow

tests/codegen/inherit_overflow.rs

@@ -4,7 +4,7 @@
 //@[NOASSERT] compile-flags: -Coverflow-checks=off
 
 // CHECK-LABEL: define{{.*}} @assertion
-// ASSERT: call void @{{.*4core9panicking5panic}}
+// ASSERT: call void @{{.*4core9panicking11panic_const24panic_const_add_overflow}}
 // NOASSERT: ret i8 0
 #[no_mangle]
 pub fn assertion() -> u8 {