Auto merge of #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 #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](#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)
 

src/test/ui/symbol-names/basic.legacy.stderr

@@ -1,10 +1,10 @@
-error: symbol-name(_ZN5basic4main17h13492e1c4157543fE)
+error: symbol-name(_ZN5basic4main17h7c2c715a9b77648bE)
   --> $DIR/basic.rs:8:1
    |
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling(basic::main::h13492e1c4157543f)
+error: demangling(basic::main::h7c2c715a9b77648b)
   --> $DIR/basic.rs:8:1
    |
 LL | #[rustc_symbol_name]

src/test/ui/symbol-names/issue-60925.legacy.stderr

@@ -1,10 +1,10 @@
-error: symbol-name(_ZN11issue_609253foo37Foo$LT$issue_60925..llv$u6d$..Foo$GT$3foo17hd250581ce0d79d13E)
+error: symbol-name(_ZN11issue_609253foo37Foo$LT$issue_60925..llv$u6d$..Foo$GT$3foo17h419983d0842a72aeE)
   --> $DIR/issue-60925.rs:21:9
    |
 LL |         #[rustc_symbol_name]
    |         ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling(issue_60925::foo::Foo<issue_60925::llvm::Foo>::foo::hd250581ce0d79d13)
+error: demangling(issue_60925::foo::Foo<issue_60925::llvm::Foo>::foo::h419983d0842a72ae)
   --> $DIR/issue-60925.rs:21:9
    |
 LL |         #[rustc_symbol_name]