[llvm] r304537 - [GlobalMerge] Don't merge globals that may be preempted

[John Brawn via llvm-commits]

Author: john.brawn
Date: Fri Jun  2 05:24:14 2017
New Revision: 304537

URL: http://llvm.org/viewvc/llvm-project?rev=304537&view=rev
Log:
[GlobalMerge] Don't merge globals that may be preempted

When a global may be preempted it needs to be accessed directly, instead of
indirectly through a MergedGlobals symbol, for the preemption to work.

This fixes PR33136.

Differential Revision: https://reviews.llvm.org/D33727

Modified:
    llvm/trunk/lib/CodeGen/GlobalMerge.cpp
    llvm/trunk/test/CodeGen/ARM/global-merge-external.ll

Modified: llvm/trunk/lib/CodeGen/GlobalMerge.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/GlobalMerge.cpp?rev=304537&r1=304536&r2=304537&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/GlobalMerge.cpp (original)
+++ llvm/trunk/lib/CodeGen/GlobalMerge.cpp Fri Jun  2 05:24:14 2017
@@ -556,6 +556,10 @@ bool GlobalMerge::doInitialization(Modul
     if (GV.isDeclaration() || GV.isThreadLocal() || GV.hasSection())
       continue;
 
+    // It's not safe to merge globals that may be preempted
+    if (TM && !TM->shouldAssumeDSOLocal(M, &GV))
+      continue;
+
     if (!(MergeExternalGlobals && GV.hasExternalLinkage()) &&
         !GV.hasInternalLinkage())
       continue;

Modified: llvm/trunk/test/CodeGen/ARM/global-merge-external.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/global-merge-external.ll?rev=304537&r1=304536&r2=304537&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/global-merge-external.ll (original)
+++ llvm/trunk/test/CodeGen/ARM/global-merge-external.ll Fri Jun  2 05:24:14 2017
@@ -2,6 +2,7 @@
 ; RUN: llc < %s -mtriple=arm-eabi  -arm-global-merge -global-merge-on-external=true  | FileCheck %s --check-prefix=CHECK-MERGE
 ; RUN: llc < %s -mtriple=arm-eabi  -arm-global-merge -global-merge-on-external=false | FileCheck %s --check-prefix=CHECK-NO-MERGE
 ; RUN: llc < %s -mtriple=arm-macho -arm-global-merge                                 | FileCheck %s --check-prefix=CHECK-NO-MERGE
+; RUN: llc < %s -mtriple=arm-eabi  -arm-global-merge -relocation-model=pic           | FileCheck %s --check-prefix=CHECK-NO-MERGE
 
 @x = global i32 0, align 4
 @y = global i32 0, align 4