From 59d960818b891ae9570bc4d152c7ca68efd8f424 Mon Sep 17 00:00:00 2001
From: Jeremy Koritzinsky <jekoritz@microsoft.com>
Date: Mon, 9 Mar 2020 10:03:08 -0700
Subject: [PATCH 1/3] Disable System.Private.CoreLib IBCMerge on MacOS.

---
 .../System.Private.CoreLib/System.Private.CoreLib.csproj    | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/coreclr/src/System.Private.CoreLib/System.Private.CoreLib.csproj b/src/coreclr/src/System.Private.CoreLib/System.Private.CoreLib.csproj
index 7e215d1ad72a8a..d0ef73e84ab162 100644
--- a/src/coreclr/src/System.Private.CoreLib/System.Private.CoreLib.csproj
+++ b/src/coreclr/src/System.Private.CoreLib/System.Private.CoreLib.csproj
@@ -20,6 +20,12 @@
     <ILLinkClearInitLocals>true</ILLinkClearInitLocals>
     <ILLinkTrimAssembly>true</ILLinkTrimAssembly>
     <ILLinkTrimXml>$(IntermediateOutputPath)System.Private.CoreLib.xml</ILLinkTrimXml>
+
+    <!-- We don't generate IBC data for the Mac-specific build of System.Private.CoreLib
+         and the Linux one is not valid for the Mac build
+         so we need to disable merging in the IBC data on the Mac build
+    -->
+    <IsEligibleForNgenOptimization Condition="'$(TargetOS)' == 'OSX'">false</IsEligibleForNgenOptimization>
   </PropertyGroup>
 
   <!-- Note that various places in SPCL depend on this resource name i.e. TplEventSource -->

From 7c8629126354477fd72480a6279aab6683e27b52 Mon Sep 17 00:00:00 2001
From: Jeremy Koritzinsky <jekoritz@microsoft.com>
Date: Mon, 9 Mar 2020 10:38:44 -0700
Subject: [PATCH 2/3] Disable IBCMerge on mac across the board.

---
 eng/codeOptimization.targets                                | 4 ++++
 .../System.Private.CoreLib/System.Private.CoreLib.csproj    | 6 ------
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/eng/codeOptimization.targets b/eng/codeOptimization.targets
index 9f135452346a24..bf143e171e3b5e 100644
--- a/eng/codeOptimization.targets
+++ b/eng/codeOptimization.targets
@@ -4,6 +4,10 @@
      <IsEligibleForNgenOptimization>true</IsEligibleForNgenOptimization>
      <IsEligibleForNgenOptimization Condition="'$(IsReferenceAssembly)' == 'true'">false</IsEligibleForNgenOptimization>
      <IsEligibleForNgenOptimization Condition="'$(GeneratePlatformNotSupportedAssembly)' == 'true' or '$(GeneratePlatformNotSupportedAssemblyMessage)' != ''">false</IsEligibleForNgenOptimization>
+      <!-- There's an issue causing IBCMerge failures across many of our assemblies on Mac, so disable
+           IBCMerge optimizations on Mac for now to unblock the offical build.
+      -->
+      <IsEligibleForNgenOptimization Condition="'$(TargetOS)' == 'OSX'">false</IsEligibleForNgenOptimization>
   </PropertyGroup>
 
   <Target Name="SetApplyNgenOptimization"
diff --git a/src/coreclr/src/System.Private.CoreLib/System.Private.CoreLib.csproj b/src/coreclr/src/System.Private.CoreLib/System.Private.CoreLib.csproj
index d0ef73e84ab162..7e215d1ad72a8a 100644
--- a/src/coreclr/src/System.Private.CoreLib/System.Private.CoreLib.csproj
+++ b/src/coreclr/src/System.Private.CoreLib/System.Private.CoreLib.csproj
@@ -20,12 +20,6 @@
     <ILLinkClearInitLocals>true</ILLinkClearInitLocals>
     <ILLinkTrimAssembly>true</ILLinkTrimAssembly>
     <ILLinkTrimXml>$(IntermediateOutputPath)System.Private.CoreLib.xml</ILLinkTrimXml>
-
-    <!-- We don't generate IBC data for the Mac-specific build of System.Private.CoreLib
-         and the Linux one is not valid for the Mac build
-         so we need to disable merging in the IBC data on the Mac build
-    -->
-    <IsEligibleForNgenOptimization Condition="'$(TargetOS)' == 'OSX'">false</IsEligibleForNgenOptimization>
   </PropertyGroup>
 
   <!-- Note that various places in SPCL depend on this resource name i.e. TplEventSource -->

From 14811761050ec9cada27eeebdadae6d625775836 Mon Sep 17 00:00:00 2001
From: Jeremy Koritzinsky <jekoritz@microsoft.com>
Date: Mon, 9 Mar 2020 11:45:00 -0700
Subject: [PATCH 3/3] Update comment to include link to issue.

---
 eng/codeOptimization.targets | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/eng/codeOptimization.targets b/eng/codeOptimization.targets
index bf143e171e3b5e..cbd2474984592a 100644
--- a/eng/codeOptimization.targets
+++ b/eng/codeOptimization.targets
@@ -4,8 +4,10 @@
      <IsEligibleForNgenOptimization>true</IsEligibleForNgenOptimization>
      <IsEligibleForNgenOptimization Condition="'$(IsReferenceAssembly)' == 'true'">false</IsEligibleForNgenOptimization>
      <IsEligibleForNgenOptimization Condition="'$(GeneratePlatformNotSupportedAssembly)' == 'true' or '$(GeneratePlatformNotSupportedAssemblyMessage)' != ''">false</IsEligibleForNgenOptimization>
-      <!-- There's an issue causing IBCMerge failures across many of our assemblies on Mac, so disable
+      <!-- There's an issue causing IBCMerge failures because of mismatched MVIDs
+           across many of our assemblies on Mac, so disable
            IBCMerge optimizations on Mac for now to unblock the offical build.
+           See issue https://github.com/dotnet/runtime/issues/33303
       -->
       <IsEligibleForNgenOptimization Condition="'$(TargetOS)' == 'OSX'">false</IsEligibleForNgenOptimization>
   </PropertyGroup>