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

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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
This commit is contained in:
bors 2024-03-29 00:24:01 +00:00
commit e8c13080f7
2 changed files with 38 additions and 16 deletions
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30
example/mini_core.rs
View File

@ -465,6 +465,36 @@ 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_bounds_check"]
#[track_caller]
fn panic_bounds_check(index: usize, len: usize) -> ! {

24
src/base.rs
View File

@ -372,8 +372,14 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
);
}
_ => {
let msg_str = msg.description();
codegen_panic(fx, msg_str, source_info);
let location = fx.get_caller_location(source_info).load_scalar(fx);
codegen_panic_inner(
fx,
msg.panic_function(),
&[location],
Some(source_info.span),
);
}
}
}
@ -957,20 +963,6 @@ pub(crate) fn codegen_operand<'tcx>(
}
}
pub(crate) fn codegen_panic<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
msg_str: &str,
source_info: mir::SourceInfo,
) {
let location = fx.get_caller_location(source_info).load_scalar(fx);
let msg_ptr = fx.anonymous_str(msg_str);
let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
let args = [msg_ptr, msg_len, location];
codegen_panic_inner(fx, rustc_hir::LangItem::Panic, &args, Some(source_info.span));
}
pub(crate) fn codegen_panic_nounwind<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
msg_str: &str,