Auto merge of rust-lang#93014 - Kobzol:revert-92103-stable-hash-skip-zero-bytes, r=the8472

Revert "Do not hash leading zero bytes of i64 numbers in Sip128 hasher"

Reverts rust-lang#92103. It had a (in retrospect, obvious) correctness problem where changing the order of two adjacent values would produce identical hashes, which is problematic in stable hashing (see [this comment](rust-lang#92103 (comment))).

I'll try to send the PR again with a fix for this issue.

r? `@the8472`

Author: bors

compiler/rustc_data_structures/src/sip128.rs

@@ -409,20 +409,6 @@ impl SipHasher128 {
     }
 }
 
-macro_rules! dispatch_value {
-    ($target: expr, $value:expr) => {
-        let value = $value;
-        #[allow(unreachable_patterns)]
-        #[allow(overflowing_literals)]
-        match value {
-            0..=0xFF => $target.short_write(value as u8),
-            0x100..=0xFFFF => $target.short_write(value as u16),
-            0x10000..=0xFFFFFFFF => $target.short_write(value as u32),
-            _ => $target.short_write(value as u64),
-        }
-    };
-}
-
 impl Hasher for SipHasher128 {
     #[inline]
     fn write_u8(&mut self, i: u8) {
@@ -436,7 +422,7 @@ impl Hasher for SipHasher128 {
 
     #[inline]
     fn write_u32(&mut self, i: u32) {
-        dispatch_value!(self, i);
+        self.short_write(i);
     }
 
     #[inline]
@@ -466,7 +452,7 @@ impl Hasher for SipHasher128 {
 
     #[inline]
     fn write_i64(&mut self, i: i64) {
-        dispatch_value!(self, i as u64);
+        self.short_write(i as u64);
     }
 
     #[inline]

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#fe3cfa0214ac55c7}>();
 // 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$3fcd7c34c1555be6> (void)
+// cdb-check:[...] a!function_names::const_generic_fn_non_int<CONST$fe3cfa0214ac55c7> (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)