[llvm] r363971 - [clang][NewPM] Do not eliminate available_externally durng `-O2 -flto` runs

[Leonard Chan via llvm-commits]

Author: leonardchan
Date: Thu Jun 20 12:44:51 2019
New Revision: 363971

URL: http://llvm.org/viewvc/llvm-project?rev=363971&view=rev
Log:
[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

Added:
    llvm/trunk/test/Other/available-externally-lto.ll
Modified:
    llvm/trunk/lib/Passes/PassBuilder.cpp

Modified: llvm/trunk/lib/Passes/PassBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Passes/PassBuilder.cpp?rev=363971&r1=363970&r2=363971&view=diff
==============================================================================
--- llvm/trunk/lib/Passes/PassBuilder.cpp (original)
+++ llvm/trunk/lib/Passes/PassBuilder.cpp Thu Jun 20 12:44:51 2019
@@ -812,8 +812,10 @@ ModulePassManager PassBuilder::buildModu
   // 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());

Added: llvm/trunk/test/Other/available-externally-lto.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Other/available-externally-lto.ll?rev=363971&view=auto
==============================================================================
--- llvm/trunk/test/Other/available-externally-lto.ll (added)
+++ llvm/trunk/test/Other/available-externally-lto.ll Thu Jun 20 12:44:51 2019
@@ -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
+
+ at 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 }