account for endianness in debuginfo for const args

Author: b-naber

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -707,12 +707,15 @@ fn push_const_param<'tcx>(tcx: TyCtxt<'tcx>, ct: ty::Const<'tcx>, output: &mut S
                 hcx.while_hashing_spans(false, |hcx| ct.to_valtree().hash_stable(hcx, &mut hasher));
                 // Let's only emit 64 bits of the hash value. That should be plenty for
                 // avoiding collisions and will make the emitted type names shorter.
-                let hash: u64 = hasher.finish();
+                // Note: Don't use `StableHashResult` impl of `u64` here directly, since that
+                // would lead to endianness problems.
+                let hash: u128 = hasher.finish();
+                let hash_short = (hash.to_le() as u64).to_le();
 
                 if cpp_like_debuginfo(tcx) {
-                    write!(output, "CONST${:x}", hash)
+                    write!(output, "CONST${:x}", hash_short)
                 } else {
-                    write!(output, "{{CONST#{:x}}}", hash)
+                    write!(output, "{{CONST#{:x}}}", hash_short)
                 }
             }
         },

src/test/debuginfo/function-names.rs

@@ -37,7 +37,7 @@
 // Const generic parameter
 // gdb-command:info functions -q function_names::const_generic_fn.*
 // gdb-check:[...]static fn function_names::const_generic_fn_bool<false>();
-// gdb-check:[...]static fn function_names::const_generic_fn_non_int<{CONST#3fcd7c34c1555be6}>();
+// gdb-check:[...]static fn function_names::const_generic_fn_non_int<{CONST#6348c650c7b26618}>();
 // gdb-check:[...]static fn function_names::const_generic_fn_signed_int<-7>();
 // gdb-check:[...]static fn function_names::const_generic_fn_unsigned_int<14>();
 
@@ -76,7 +76,7 @@
 // Const generic parameter
 // cdb-command:x a!function_names::const_generic_fn*
 // cdb-check:[...] a!function_names::const_generic_fn_bool<false> (void)
-// cdb-check:[...] a!function_names::const_generic_fn_non_int<CONST$3fcd7c34c1555be6> (void)
+// cdb-check:[...] a!function_names::const_generic_fn_non_int<CONST$6348c650c7b26618> (void)
 // cdb-check:[...] a!function_names::const_generic_fn_unsigned_int<14> (void)
 // cdb-check:[...] a!function_names::const_generic_fn_signed_int<-7> (void)