From d6312bbbbd7739c8bfd8cc1ddad7662b1c6ee158 Mon Sep 17 00:00:00 2001
From: Gerolf Hoflehner <ghoflehner@apple.com>
Date: Thu, 17 Apr 2014 00:21:52 +0000
Subject: [PATCH 1/1] Inline a function when the always_inline attribute is set
 even when it contains a indirect branch. The attribute overrules correctness
 concerns like the escape of a local block address.

This is for rdar://16501761




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206429 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/IPA/InlineCost.cpp               | 10 +++++--
 .../Inline/always-inline-attribute.ll         | 26 +++++++++++++++++++
 test/Transforms/Inline/always-inline.ll       |  2 +-
 3 files changed, 35 insertions(+), 3 deletions(-)
 create mode 100644 test/Transforms/Inline/always-inline-attribute.ll

diff --git a/lib/Analysis/IPA/InlineCost.cpp b/lib/Analysis/IPA/InlineCost.cpp
index a803f8c3bf9..683637f5b7f 100644
--- a/lib/Analysis/IPA/InlineCost.cpp
+++ b/lib/Analysis/IPA/InlineCost.cpp
@@ -1300,8 +1300,14 @@ bool InlineCostAnalysis::isInlineViable(Function &F) {
     F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
                                    Attribute::ReturnsTwice);
   for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
-    // Disallow inlining of functions which contain an indirect branch.
-    if (isa<IndirectBrInst>(BI->getTerminator()))
+    // Disallow inlining of functions which contain an indirect branch,
+    // unless the always_inline attribute is set.
+    // The attribute serves as a assertion that no local address
+    // like a block label can escpape the function.
+    // Revisit enabling inlining for functions with indirect branches
+    // when a more sophisticated espape/points-to analysis becomes available.
+    if (isa<IndirectBrInst>(BI->getTerminator()) &&
+        !F.hasFnAttribute(Attribute::AlwaysInline))
       return false;
 
     for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;
diff --git a/test/Transforms/Inline/always-inline-attribute.ll b/test/Transforms/Inline/always-inline-attribute.ll
new file mode 100644
index 00000000000..c146122e163
--- /dev/null
+++ b/test/Transforms/Inline/always-inline-attribute.ll
@@ -0,0 +1,26 @@
+; RUN: opt < %s -O3 -S | FileCheck %s
+@gv = external global i32
+
+define i32 @main() nounwind {
+; CHECK-NOT: call i32 @foo
+  %1 = load i32* @gv, align 4
+  %2 = tail call i32 @foo(i32 %1)
+  unreachable
+}
+
+define internal i32 @foo(i32) alwaysinline {
+  br label %2
+
+; <label>:2                                       ; preds = %8, %1
+  %3 = phi i32 [ %0, %1 ], [ %10, %8 ]
+  %4 = phi i8* [ blockaddress(@foo, %2), %1 ], [ %6, %8 ]
+  %5 = icmp eq i32 %3, 1
+  %6 = select i1 %5, i8* blockaddress(@foo, %8), i8* %4
+  %7 = add nsw i32 %3, -1
+  br label %8
+
+; <label>:8                                       ; preds = %8, %2
+  %9 = phi i32 [ %7, %2 ], [ %10, %8 ]
+  %10 = add nsw i32 %9, -1
+  indirectbr i8* %6, [label %2, label %8]
+}
diff --git a/test/Transforms/Inline/always-inline.ll b/test/Transforms/Inline/always-inline.ll
index a8703b89877..832e000eacc 100644
--- a/test/Transforms/Inline/always-inline.ll
+++ b/test/Transforms/Inline/always-inline.ll
@@ -78,7 +78,7 @@ entry:
   ret i32 %add
 }
 
-define i32 @inner5(i8* %addr) alwaysinline {
+define i32 @inner5(i8* %addr) {
 entry:
   indirectbr i8* %addr, [ label %one, label %two ]
 
-- 
2.34.1