From 723446a749fc5b4492500932dd39618310f9b646 Mon Sep 17 00:00:00 2001
From: Cody Tapscott <topolarity@tapscott.me>
Date: Wed, 19 Nov 2025 17:46:22 -0500
Subject: [PATCH] Add Preference to disable runtime invalidation

This makes the package (nearly) `--trim` compatible and also provides a
nice preference for users who do not wish for HostCPUFeatures.jl to ever
cause an "invalidation storm", even if it means running with the wrong
CPU info.
---
 Project.toml            |  1 +
 src/HostCPUFeatures.jl  | 14 +++++++++++---
 src/cpu_info.jl         | 19 ++++++++++++++-----
 src/cpu_info_aarch64.jl | 14 ++++++++++++--
 src/cpu_info_x86.jl     | 16 ++++++++++++----
 5 files changed, 50 insertions(+), 14 deletions(-)

diff --git a/Project.toml b/Project.toml
index 0fc7612..fe96591 100644
--- a/Project.toml
+++ b/Project.toml
@@ -7,6 +7,7 @@ version = "0.1.17"
 BitTwiddlingConvenienceFunctions = "62783981-4cbd-42fc-bca8-16325de8dc4b"
 IfElse = "615f187c-cbe4-4ef1-ba3b-2fcf58d6d173"
 Libdl = "8f399da3-3557-5675-b5ff-fb832c97cbdb"
+Preferences = "21216c6a-2e73-6563-6e65-726566657250"
 Static = "aedffcd0-7271-4cad-89d0-dc628f76c6d3"
 
 [compat]
diff --git a/src/HostCPUFeatures.jl b/src/HostCPUFeatures.jl
index 3e8b5ba..700475e 100644
--- a/src/HostCPUFeatures.jl
+++ b/src/HostCPUFeatures.jl
@@ -7,6 +7,7 @@ end
 using Libdl, Static
 using Static: Zero, One, lt, gt
 using IfElse: ifelse
+using Preferences
 
 using BitTwiddlingConvenienceFunctions: prevpow2, nextpow2, intlog2
 
@@ -37,19 +38,26 @@ unwrap(::StaticSymbol{S}) where {S} = S
 
 @noinline function redefine()
   @debug "Defining CPU name."
-  define_cpu_name()
+  redefine_cpu_name()
 
   reset_features!()
   reset_extra_features!()
 end
 const BASELINE_CPU_NAME = get_cpu_name()
+const allow_eval = @load_preference("allow_runtime_invalidation", false)
+
 function __init__()
   ccall(:jl_generating_output, Cint, ()) == 1 && return
   if Sys.ARCH === :x86_64 || Sys.ARCH === :i686
     target = Base.unsafe_string(Base.JLOptions().cpu_target)
-    occursin("native",  target) || return make_generic(target)
+    if !occursin("native",  target)
+      make_generic(target)
+      return nothing
+    end
+  end
+  if BASELINE_CPU_NAME != Sys.CPU_NAME::String
+    redefine()
   end
-  BASELINE_CPU_NAME == Sys.CPU_NAME::String || redefine()
   return nothing
 end
 
diff --git a/src/cpu_info.jl b/src/cpu_info.jl
index 52b49fe..ca35d83 100644
--- a/src/cpu_info.jl
+++ b/src/cpu_info.jl
@@ -48,8 +48,12 @@ function reset_features!()
     for ext ∈ features
         feature, has = process_feature(ext)
         if _has_feature(feature) ≠ has
-            @debug "Defining $(has ? "presence" : "absense") of feature $feature."
-            set_feature(feature, has)
+            if allow_eval
+                @debug "Defining $(has ? "presence" : "absense") of feature $feature."
+                set_feature(feature, has)
+            else
+                @warn "Runtime invalidation was disabled, but the CPU info is out-of-date.\nWill continue with incorrect CPU feature flag: $ext."
+            end
         end
     end
     Libc.free(features_cstring)
@@ -58,8 +62,13 @@ end
 register_size(::Type{T}) where {T} = register_size()
 register_size(::Type{T}) where {T<:Union{Signed,Unsigned}} = simd_integer_register_size()
 
-function define_cpu_name()
+function redefine_cpu_name()
     cpu = QuoteNode(Symbol(get_cpu_name()))
-    @eval cpu_name() = Val{$cpu}()
+    if allow_eval
+      @eval cpu_name() = Val{$cpu}()
+    else
+      @warn "Runtime invalidation was disabled, but the CPU info is out-of-date.\nWill continue with incorrect CPU name (from build time)."
+    end
 end
-define_cpu_name()
+cpu = QuoteNode(Symbol(get_cpu_name()))
+@eval cpu_name() = Val{$cpu}()
diff --git a/src/cpu_info_aarch64.jl b/src/cpu_info_aarch64.jl
index 605d54d..ffa64d6 100644
--- a/src/cpu_info_aarch64.jl
+++ b/src/cpu_info_aarch64.jl
@@ -39,10 +39,20 @@ end
 
 function reset_extra_features!()
     drs = _dynamic_register_size()
-    register_size() ≠ drs && _set_sve_vector_width!(drs)
+    if register_size() ≠ drs
+        if allow_eval
+            _set_sve_vector_width!(drs)
+        else
+            @warn "Runtime invalidation was disabled, but the CPU info is out-of-date.\nWill continue with incorrect CPU register size."
+        end
+    end
     hassve = _has_aarch64_sve()
     if hassve ≠ has_feature(Val(:aarch64_sve_cpuid))
-        @eval has_feature(::Val{:aarch64_sve_cpuid}) = $(Expr(:call, hassve ? :True : :False))
+        if allow_eval
+            @eval has_feature(::Val{:aarch64_sve_cpuid}) = $(Expr(:call, hassve ? :True : :False))
+        else
+            @warn "Runtime invalidation was disabled, but the CPU info is out-of-date.\nWill continue with incorrect CPU feature flag: :aarch64_sve_cpuid."
+        end
     end
 end
 
diff --git a/src/cpu_info_x86.jl b/src/cpu_info_x86.jl
index b0348c0..7550729 100644
--- a/src/cpu_info_x86.jl
+++ b/src/cpu_info_x86.jl
@@ -32,14 +32,22 @@ fast_int64_to_double() = has_feature(Val(:x86_64_avx512dq))
 
 fast_half() = False()
 
-@noinline function setfeaturefalse(s)
+@inline function setfeaturefalse(s)
   if has_feature(Val(s)) === True()
-    @eval has_feature(::Val{$(QuoteNode(s))}) = False()
+    if allow_eval
+      @eval has_feature(::Val{$(QuoteNode(s))}) = False()
+    else
+      @warn "Runtime invalidation was disabled, but the CPU info is out-of-date.\nWill continue with incorrect CPU feature flag: $s."
+    end
   end
 end
-@noinline function setfeaturetrue(s)
+@inline function setfeaturetrue(s)
   if has_feature(Val(s)) === False()
-    @eval has_feature(::Val{$(QuoteNode(s))}) = True()
+    if allow_eval
+      @eval has_feature(::Val{$(QuoteNode(s))}) = True()
+    else
+      @warn "Runtime invalidation was disabled, but the CPU info is out-of-date.\nWill continue with incorrect CPU feature flag: $s."
+    end
   end
 end