Auto merge of rust-lang#108446 - Zoxc:named-allocs, r=oli-obk

Name LLVM anonymous constants by a hash of their contents

This makes the names stable between different versions of a crate unlike the `AllocId` naming, making LLVM IR comparisons with `llvm-diff` more practical.

Author: bors

compiler/rustc_codegen_llvm/src/common.rs

@@ -10,6 +10,7 @@ use crate::value::Value;
 use rustc_ast::Mutability;
 use rustc_codegen_ssa::mir::place::PlaceRef;
 use rustc_codegen_ssa::traits::*;
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_hir::def_id::DefId;
 use rustc_middle::bug;
 use rustc_middle::mir::interpret::{ConstAllocation, GlobalAlloc, Scalar};
@@ -252,8 +253,13 @@ impl<'ll, 'tcx> ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                             Mutability::Mut => self.static_addr_of_mut(init, alloc.align, None),
                             _ => self.static_addr_of(init, alloc.align, None),
                         };
-                        if !self.sess().fewer_names() {
-                            llvm::set_value_name(value, format!("{:?}", alloc_id).as_bytes());
+                        if !self.sess().fewer_names() && llvm::get_value_name(value).is_empty() {
+                            let hash = self.tcx.with_stable_hashing_context(|mut hcx| {
+                                let mut hasher = StableHasher::new();
+                                alloc.hash_stable(&mut hcx, &mut hasher);
+                                hasher.finish::<u128>()
+                            });
+                            llvm::set_value_name(value, format!("alloc_{hash:032x}").as_bytes());
                         }
                         (value, AddressSpace::DATA)
                     }

tests/codegen/consts.rs

@@ -9,11 +9,11 @@
 // CHECK: @STATIC = {{.*}}, align 4
 
 // This checks the constants from inline_enum_const
-// CHECK: @alloc12 = {{.*}}, align 2
+// CHECK: @alloc_76bfe2f13a3e3b01074971d122eac57e = {{.*}}, align 2
 
 // This checks the constants from {low,high}_align_const, they share the same
 // constant, but the alignment differs, so the higher one should be used
-// CHECK: [[LOW_HIGH:@alloc[0-9]+]] = {{.*}}, align 4
+// CHECK: [[LOW_HIGH:@alloc_[a-f0-9]+]] = {{.*}}, align 4
 
 #[derive(Copy, Clone)]
 // repr(i16) is required for the {low,high}_align_const test

tests/codegen/remap_path_prefix/main.rs

@@ -12,7 +12,7 @@ mod aux_mod;
 include!("aux_mod.rs");
 
 // Here we check that the expansion of the file!() macro is mapped.
-// CHECK: @alloc2 = private unnamed_addr constant <{ [34 x i8] }> <{ [34 x i8] c"/the/src/remap_path_prefix/main.rs" }>
+// CHECK: @alloc_92a59126a55aa3c0019b6c8a007fe001 = private unnamed_addr constant <{ [34 x i8] }> <{ [34 x i8] c"/the/src/remap_path_prefix/main.rs" }>
 pub static FILE_PATH: &'static str = file!();
 
 fn main() {