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Auto merge of #130052 - khuey:clear-dilocation-after-const-emission, r=michaelwoerister

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Don't leave debug locations for constants sitting on the builder indefinitely

Because constants are currently emitted *before* the prologue, leaving the debug location on the IRBuilder spills onto other instructions in the prologue and messes up both line numbers as well as the point LLVM chooses to be the prologue end.

Example LLVM IR (irrelevant IR elided):
Before:
```
define internal { i64, i64 } `@_ZN3tmp3Foo18var_return_opt_try17he02116165b0fc08cE(ptr` align 8 %self) !dbg !347 { start:
  %self.dbg.spill = alloca [8 x i8], align 8
  %_0 = alloca [16 x i8], align 8
  %residual.dbg.spill = alloca [0 x i8], align 1
    #dbg_declare(ptr %residual.dbg.spill, !353, !DIExpression(), !357)
  store ptr %self, ptr %self.dbg.spill, align 8, !dbg !357
    #dbg_declare(ptr %self.dbg.spill, !350, !DIExpression(), !358)
```
After:
```
define internal { i64, i64 } `@_ZN3tmp3Foo18var_return_opt_try17h00b17d08874ddd90E(ptr` align 8 %self) !dbg !347 { start:
  %self.dbg.spill = alloca [8 x i8], align 8
  %_0 = alloca [16 x i8], align 8
  %residual.dbg.spill = alloca [0 x i8], align 1
    #dbg_declare(ptr %residual.dbg.spill, !353, !DIExpression(), !357)
  store ptr %self, ptr %self.dbg.spill, align 8
    #dbg_declare(ptr %self.dbg.spill, !350, !DIExpression(), !358)
```
Note in particular how !357 from %residual.dbg.spill's dbg_declare no longer falls through onto the store to %self.dbg.spill. This fixes argument values at entry when the constant is a ZST (e.g. `<Option as Try>::Residual`). This fixes #130003 (but note that it does *not* fix issues with argument values and non-ZST constants, which emit their own stores that have debug info on them, like #128945).

r? `@michaelwoerister`
This commit is contained in:
bors 2024-09-13 08:57:41 +00:00
commit 5e842953cc
6 changed files with 86 additions and 2 deletions
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72
tests/debuginfo/zst-interferes-with-prologue.rs Normal file
View file

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//@ min-lldb-version: 310
//@ compile-flags:-g
// === GDB TESTS ===================================================================================
// gdb-command:break zst_interferes_with_prologue::Foo::var_return_opt_try
// gdb-command:run
// gdb-command:print self
// gdb-command:next
// gdb-command:print self
// gdb-command:print $1 == $2
// gdb-check:true
// === LLDB TESTS ==================================================================================
// lldb-command:b "zst_interferes_with_prologue::Foo::var_return_opt_try"
// lldb-command:run
// lldb-command:expr self
// lldb-command:next
// lldb-command:expr self
// lldb-command:print $0 == $1
// lldb-check:true
struct Foo {
a: usize,
}
impl Foo {
#[inline(never)]
fn get_a(&self) -> Option<usize> {
Some(self.a)
}
#[inline(never)]
fn var_return(&self) -> usize {
let r = self.get_a().unwrap();
r
}
#[inline(never)]
fn var_return_opt_unwrap(&self) -> Option<usize> {
let r = self.get_a().unwrap();
Some(r)
}
#[inline(never)]
fn var_return_opt_match(&self) -> Option<usize> {
let r = match self.get_a() {
None => return None,
Some(a) => a,
};
Some(r)
}
#[inline(never)]
fn var_return_opt_try(&self) -> Option<usize> {
let r = self.get_a()?;
Some(r)
}
}
fn main() {
let f1 = Foo{ a: 1 };
let f2 = Foo{ a: 1 };
f1.var_return();
f1.var_return_opt_unwrap();
f1.var_return_opt_match();
f2.var_return_opt_try();
}