[PATCH] D86988: [Inliner] Run always-inliner in inliner-wrapper

[Arthur Eubanks via Phabricator via llvm-commits]

aeubanks created this revision.
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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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D86988

Files:
  llvm/lib/Transforms/IPO/Inliner.cpp
  llvm/test/Transforms/Inline/pr46945.ll


Index: llvm/test/Transforms/Inline/pr46945.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Inline/pr46945.ll
@@ -0,0 +1,18 @@
+; RUN: opt %s -o - -S -passes=inliner-wrapper | FileCheck %s
+
+; CHECK-NOT: call void @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
+}
+
Index: llvm/lib/Transforms/IPO/Inliner.cpp
===================================================================
--- llvm/lib/Transforms/IPO/Inliner.cpp
+++ 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"
@@ -1055,6 +1056,7 @@
     return PreservedAnalyses::all();
   }
 
+  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


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