From 374c734d9b3f8e6fa20810ad4d049ca2711e2156 Mon Sep 17 00:00:00 2001
From: Claudia <claui@users.noreply.github.com>
Date: Wed, 8 Jul 2020 20:53:10 +0200
Subject: [PATCH] Make `Hardware.oldest_cpu` depend on architecture

Starting with Xcode 12 Beta 2, builds that used to work on Apple Silicon
now break due to `Hardware#oldest_cpu` returning `:nehalem` [1].

This commit is the first in a series of improvements to
`Hardware#oldest_cpu`. It resolves the Xcode 12 Beta 2 issue for now.

[1]: https://github.com/Homebrew/brew/issues/7857#issuecomment-655536261
---
 Library/Homebrew/extend/os/mac/hardware.rb   |  4 +++-
 Library/Homebrew/hardware.rb                 | 17 +++++++++--------
 Library/Homebrew/os/mac/version.rb           |  4 ++++
 Library/Homebrew/test/os/mac/version_spec.rb |  1 +
 4 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/Library/Homebrew/extend/os/mac/hardware.rb b/Library/Homebrew/extend/os/mac/hardware.rb
index b41439350f..c1edebfa6d 100644
--- a/Library/Homebrew/extend/os/mac/hardware.rb
+++ b/Library/Homebrew/extend/os/mac/hardware.rb
@@ -2,7 +2,9 @@
 
 module Hardware
   def self.oldest_cpu(version = MacOS.version)
-    if version >= :mojave
+    if CPU.arch == :arm64
+      :arm_vortex_tempest
+    elsif version >= :mojave
       :nehalem
     else
       generic_oldest_cpu
diff --git a/Library/Homebrew/hardware.rb b/Library/Homebrew/hardware.rb
index e056439d54..789b34fb9c 100644
--- a/Library/Homebrew/hardware.rb
+++ b/Library/Homebrew/hardware.rb
@@ -12,14 +12,15 @@ module Hardware
     class << self
       def optimization_flags
         @optimization_flags ||= {
-          native:  arch_flag("native"),
-          nehalem: "-march=nehalem",
-          core2:   "-march=core2",
-          core:    "-march=prescott",
-          armv6:   "-march=armv6",
-          armv8:   "-march=armv8-a",
-          ppc64:   "-mcpu=powerpc64",
-          ppc64le: "-mcpu=powerpc64le",
+          native:             arch_flag("native"),
+          nehalem:            "-march=nehalem",
+          core2:              "-march=core2",
+          core:               "-march=prescott",
+          arm_vortex_tempest: "",
+          armv6:              "-march=armv6",
+          armv8:              "-march=armv8-a",
+          ppc64:              "-mcpu=powerpc64",
+          ppc64le:            "-mcpu=powerpc64le",
         }.freeze
       end
       alias generic_optimization_flags optimization_flags
diff --git a/Library/Homebrew/os/mac/version.rb b/Library/Homebrew/os/mac/version.rb
index 23bf6b178c..f80c225744 100644
--- a/Library/Homebrew/os/mac/version.rb
+++ b/Library/Homebrew/os/mac/version.rb
@@ -43,6 +43,10 @@ module OS
 
       # For OS::Mac::Version compatibility
       def requires_nehalem_cpu?
+        unless Hardware::CPU.intel?
+          raise "Unexpected architecture: #{Hardware::CPU.arch}. This only works with Intel architecture."
+        end
+
         Hardware.oldest_cpu(self) == :nehalem
       end
       # https://en.wikipedia.org/wiki/Nehalem_(microarchitecture)
diff --git a/Library/Homebrew/test/os/mac/version_spec.rb b/Library/Homebrew/test/os/mac/version_spec.rb
index 1d57fdbe0d..40c51974cb 100644
--- a/Library/Homebrew/test/os/mac/version_spec.rb
+++ b/Library/Homebrew/test/os/mac/version_spec.rb
@@ -50,6 +50,7 @@ describe OS::Mac::Version do
   end
 
   specify "#requires_nehalem_cpu?" do
+    expect(Hardware::CPU).to receive(:type).at_least(:twice).and_return(:intel)
     expect(described_class.new("10.14").requires_nehalem_cpu?).to be true
     expect(described_class.new("10.12").requires_nehalem_cpu?).to be false
   end