From: Tim Northover <tnorthover@apple.com>
Date: Tue, 14 Oct 2014 20:57:26 +0000 (+0000)
Subject: ARM: set preferred aggregate alignment to 32 universally.
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=commitdiff_plain;h=eddeac0b8c80895e3523b4d9af6334ff4a521d7d

ARM: set preferred aggregate alignment to 32 universally.

Before, ARM and Thumb mode code had different preferred alignments, which could
lead to some rather unexpected results. There's justification for reducing it
from the default 64-bits (wasted space), but I don't think there is for going
below 32-bits.

There's no actual ABI change here, just to reassure people.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219719 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/ARM/ARMSubtarget.cpp b/lib/Target/ARM/ARMSubtarget.cpp
index a3ade981740..bc04f37331e 100644
--- a/lib/Target/ARM/ARMSubtarget.cpp
+++ b/lib/Target/ARM/ARMSubtarget.cpp
@@ -123,10 +123,9 @@ static std::string computeDataLayout(ARMSubtarget &ST) {
   else
     Ret += "-v128:64:128";
 
-  // On thumb and APCS, only try to align aggregates to 32 bits (the default is
-  // 64 bits).
-  if (ST.isThumb() || ST.isAPCS_ABI())
-    Ret += "-a:0:32";
+  // Try to align aggregates to 32 bits (the default is 64 bits, which has no
+  // particular hardware support on 32-bit ARM).
+  Ret += "-a:0:32";
 
   // Integer registers are 32 bits.
   Ret += "-n32";
diff --git a/test/CodeGen/ARM/aggregate-align.ll b/test/CodeGen/ARM/aggregate-align.ll
new file mode 100644
index 00000000000..22fc57c1de7
--- /dev/null
+++ b/test/CodeGen/ARM/aggregate-align.ll
@@ -0,0 +1,6 @@
+; RUN: llc -mtriple=armv7-linux-gnueabi %s -o - | FileCheck %s
+
+@var = global {i8, i8} zeroinitializer
+
+; CHECK: .globl var
+; CHECK-NEXT: .align 2