commit 0291e2c9330930bd74bfb8206cf6447a84bf492c
Author: Arthur Eubanks <aeubanks@google.com>
Date:   Tue Sep 1 15:55:05 2020 -0700

    [Inliner] Run always-inliner in inliner-wrapper
    
    An alwaysinline function may not get inlined in inliner-wrapper due to
    the inlining order.
    
    Previously for the following, the inliner would first inline @a() into @b(),
    
    ```
    define void @a() {
    entry:
      call void @b()
      ret void
    }
    
    define void @b() alwaysinline {
    entry:
      br label %for.cond
    
    for.cond:
      call void @a()
      br label %for.cond
    }
    ```
    
    making @b() recursive and unable to be inlined into @a(), ending at
    
    ```
    define void @a() {
    entry:
      call void @b()
      ret void
    }
    
    define void @b() alwaysinline {
    entry:
      br label %for.cond
    
    for.cond:
      call void @b()
      br label %for.cond
    }
    ```
    
    Running always-inliner first makes sure that we respect alwaysinline in more cases.
    
    Fixes https://bugs.llvm.org/show_bug.cgi?id=46945.
    
    Reviewed By: davidxl, rnk
    
    Differential Revision: https://reviews.llvm.org/D86988

diff --git a/llvm/lib/Transforms/IPO/Inliner.cpp b/llvm/lib/Transforms/IPO/Inliner.cpp
index 7d2260f4c169..540042e5f069 100644
--- a/llvm/lib/Transforms/IPO/Inliner.cpp
+++ b/llvm/lib/Transforms/IPO/Inliner.cpp
@@ -58,6 +58,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/IPO/AlwaysInliner.h"
 #include "llvm/Transforms/Utils/CallPromotionUtils.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 #include "llvm/Transforms/Utils/ImportedFunctionsInliningStatistics.h"
@@ -91,6 +92,11 @@ static cl::opt<bool>
     DisableInlinedAllocaMerging("disable-inlined-alloca-merging",
                                 cl::init(false), cl::Hidden);
 
+/// Flag to disable adding AlwaysInlinerPass to ModuleInlinerWrapperPass.
+/// TODO: remove this once this has is baked in for long enough.
+static cl::opt<bool> DisableAlwaysInlinerInModuleWrapper(
+    "disable-always-inliner-in-module-wrapper", cl::init(false), cl::Hidden);
+
 namespace {
 
 enum class InlinerFunctionImportStatsOpts {
@@ -1055,6 +1061,8 @@ PreservedAnalyses ModuleInlinerWrapperPass::run(Module &M,
     return PreservedAnalyses::all();
   }
 
+  if (!DisableAlwaysInlinerInModuleWrapper)
+    MPM.addPass(AlwaysInlinerPass());
   // We wrap the CGSCC pipeline in a devirtualization repeater. This will try
   // to detect when we devirtualize indirect calls and iterate the SCC passes
   // in that case to try and catch knock-on inlining or function attrs