Remove :salted-symbol-hash as a choice

crossbuild-runner/backends/arm/features

@@ -4,4 +4,3 @@
 ; hooks in for someone to add the support later.
 :arm-vfp :arm-vfpv2
 :fp-and-pc-standard-save
-:salted-symbol-hash

crossbuild-runner/backends/mips/features

@@ -1,3 +1,2 @@
 :gencgc :use-cons-region :soft-card-marks
 :alien-callbacks
-:salted-symbol-hash

crossbuild-runner/backends/ppc/features

@@ -1,3 +1,2 @@
 :gencgc
 :compare-and-swap-vops :alien-callbacks
-:salted-symbol-hash

crossbuild-runner/backends/sparc/features

@@ -1,2 +1 @@
 :gencgc
-:salted-symbol-hash

crossbuild-runner/backends/x86/features

@@ -6,4 +6,3 @@
 :alien-callbacks
 :cycle-counter
 :fp-and-pc-standard-save
-:salted-symbol-hash

src/code/cross-sxhash.lisp

@@ -58,9 +58,8 @@
              most-positive-fixnum)))
 
 (defun sxhash-symbol-xform (s)
-  #-salted-symbol-hash `(symbol-hash ,s)
-  #+(and salted-symbol-hash 64-bit) `(let ((h (symbol-name-hash ,s))) (sb-int:mix h h))
-  #+(and salted-symbol-hash (not 64-bit)) `(symbol-name-hash ,s))
+  #+64-bit `(let ((h (symbol-name-hash ,s))) (sb-int:mix h h)) ; get 60ish bits from 32
+  #-64-bit `(symbol-name-hash ,s))
 ) ; end EVAL-WHEN
 
 (defun calc-symbol-name-hash (string length)

src/code/symbol.lisp

@@ -392,8 +392,6 @@ distinct from the global value. Can also be SETF."
        (name-hash (calc-symbol-name-hash name (length name)))
        (symbol #+x86-64 (symbol-allocator-macro kind name)
                #-x86-64 (sb-vm::%alloc-symbol name)))
-    #-salted-symbol-hash (%set-symbol-hash symbol name-hash)
-    #+salted-symbol-hash
     (let ((salt (murmur-hash-word/fixnum
                  (word-mix name-hash (get-lisp-obj-address symbol)))))
       #+64-bit

src/cold/shared.lisp

@@ -319,12 +319,6 @@
           (pushnew :immobile-code sb-xc:*features*))
         (when (target-featurep :64-bit)
           (push :compact-symbol sb-xc:*features*))
-        (when (target-featurep :64-bit)
-          ;; Considering that a single config file governs rv32 and rv64, I don't
-          ;; know how to make this properly configurable. In theory, 32-bit builds could
-          ;; have a salted hash (gaining 3 bits by making the hash slot raw), but
-          ;; they don't, so in light of things, this is a valid criterion.
-          (push :salted-symbol-hash sb-xc:*features*))
         (when (target-featurep '(:and :sb-thread (:or (:and :darwin (:not (:or :ppc :x86))) :openbsd)))
           (push :os-thread-stack sb-xc:*features*))
         (when (target-featurep '(:and :x86 :int4-breakpoints))

src/compiler/generic/genesis.lisp

@@ -1154,9 +1154,6 @@ core and return a descriptor to it."
 (defun assign-symbol-hash (descriptor wordindex name)
   ;; "why not just call sb-c::symbol-name-hash?" you ask? because: no symbol.
   (let ((name-hash (sb-c::calc-symbol-name-hash name (length name))))
-    #-salted-symbol-hash
-    (write-wordindexed descriptor wordindex (make-fixnum-descriptor name-hash))
-    #+salted-symbol-hash
     (let* ((salt (sb-impl::murmur3-fmix-word (descriptor-bits descriptor)))
            (prng-byte sb-impl::symbol-hash-prng-byte)
            ;; 64-bit: Low 4 bytes to high 4 bytes of slot

src/compiler/generic/objdef.lisp

@@ -433,8 +433,7 @@ during backtrace.
         :init :null)
   (name :init :arg :ref-trans symbol-name)
   ;; The remaining slots can be ignored by GC
-  #+salted-symbol-hash (hash)
-  #-salted-symbol-hash (hash :set-trans %set-symbol-hash :ref-trans symbol-hash)
+  (hash)
   (package-id :type index ; actually 16 bits. (Could go in the header)
               :ref-trans symbol-package-id
               :set-trans sb-impl::set-symbol-package-id :set-known ())

src/compiler/sxhash.lisp

@@ -167,9 +167,6 @@
 (deftransform hash-as-if-symbol-name ((object) (symbol) * :important nil)
   `(symbol-name-hash object))
 
-#-salted-symbol-hash
-(define-source-transform symbol-name-hash (s) `(ldb (byte 32 0) (symbol-hash ,s)))
-
 (intern "SCRAMBLE" "SB-C")
 (intern "TAB" "SB-C")
 

tests/symbol.pure.lisp

@@ -126,7 +126,7 @@
     (values (/ n-well-hashed-sets n-homograph-sets)
             result)))
 
-(with-test (:name :hashing-improvements :skipped-on (not :salted-symbol-hash))
+(with-test (:name :hashing-improvements)
   ;; Roughly: For each set of symbols colliding on SXHASH at all, what fraction
   ;; of those sets do NOT have any collisions on SYMBOL-HASH.
   (let ((expectation