From: Leonard Chan <leonardchan@google.com>
Date: Thu, 20 Jun 2019 19:44:51 +0000 (+0000)
Subject: [clang][NewPM] Do not eliminate available_externally durng `-O2 -flto` runs
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=0d6fe2eaa443182637f01e799a0b1cea96a77a4c;p=llvm

[clang][NewPM] Do not eliminate available_externally durng `-O2 -flto` runs

This fixes CodeGen/available-externally-suppress.c when the new pass manager is
turned on by default. available_externally was not emitted during -O2 -flto
runs when it should still be retained for link time inlining purposes. This can
be fixed by checking that we aren't LTOPrelinking when adding the
EliminateAvailableExternallyPass.

Differential Revision: https://reviews.llvm.org/D63580

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@363971 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Passes/PassBuilder.cpp b/lib/Passes/PassBuilder.cpp
index 2da923086b2..bd7ec65052a 100644
--- a/lib/Passes/PassBuilder.cpp
+++ b/lib/Passes/PassBuilder.cpp
@@ -812,8 +812,10 @@ ModulePassManager PassBuilder::buildModuleOptimizationPipeline(
   // available externally globals. Eventually they will be suppressed during
   // codegen, but eliminating here enables more opportunity for GlobalDCE as it
   // may make globals referenced by available external functions dead and saves
-  // running remaining passes on the eliminated functions.
-  MPM.addPass(EliminateAvailableExternallyPass());
+  // running remaining passes on the eliminated functions. These should be
+  // preserved during prelinking for link-time inlining decisions.
+  if (!LTOPreLink)
+    MPM.addPass(EliminateAvailableExternallyPass());
 
   if (EnableOrderFileInstrumentation)
     MPM.addPass(InstrOrderFilePass());
diff --git a/test/Other/available-externally-lto.ll b/test/Other/available-externally-lto.ll
new file mode 100644
index 00000000000..e7f5e0e0ec2
--- /dev/null
+++ b/test/Other/available-externally-lto.ll
@@ -0,0 +1,23 @@
+; Ensure that we don't emit available_externally functions at -O2, unless
+; -flto is present in which case we should preserve them for link-time inlining
+; decisions.
+; RUN: opt < %s -S -passes='default<O2>' | FileCheck %s
+; RUN: opt < %s -S -passes='lto-pre-link<O2>' | FileCheck %s --check-prefix=LTO
+
+@x = common local_unnamed_addr global i32 0, align 4
+
+define void @test() local_unnamed_addr #0 {
+entry:
+  tail call void @f0(i32 17)
+  ret void
+}
+
+; CHECK: declare void @f0(i32)
+; LTO: define available_externally void @f0(i32 %y)
+define available_externally void @f0(i32 %y) local_unnamed_addr #0 {
+entry:
+  store i32 %y, i32* @x, align 4
+  ret void
+}
+
+attributes #0 = { noinline }