From: Tim Northover <Tim.Northover@arm.com>
Date: Thu, 28 Feb 2013 14:36:31 +0000 (+0000)
Subject: AArch64: be more careful resorting to inefficient addressing for weak vars.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6ff20f205b2aa126b268bcada9920f56715161be;p=oota-llvm.git

AArch64: be more careful resorting to inefficient addressing for weak vars.

If an otherwise weak var is actually defined in this unit, it can't be
undefined at runtime so we can use normal global variable sequences (ADRP/ADD)
to access it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176259 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/AArch64/AArch64ISelLowering.cpp b/lib/Target/AArch64/AArch64ISelLowering.cpp
index fa9dcbfc21f..34cc0e3b3b8 100644
--- a/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -1852,11 +1852,10 @@ AArch64TargetLowering::LowerGlobalAddressELF(SDValue Op,
   const GlobalValue *GV = GN->getGlobal();
   unsigned Alignment = GV->getAlignment();
   Reloc::Model RelocM = getTargetMachine().getRelocationModel();
-
-  if (GV->isWeakForLinker() && RelocM == Reloc::Static) {
-    // Weak symbols can't use ADRP/ADD pair since they should evaluate to
-    // zero when undefined. In PIC mode the GOT can take care of this, but in
-    // absolute mode we use a constant pool load.
+  if (GV->isWeakForLinker() && GV->isDeclaration() && RelocM == Reloc::Static) {
+    // Weak undefined symbols can't use ADRP/ADD pair since they should evaluate
+    // to zero when they remain undefined. In PIC mode the GOT can take care of
+    // this, but in absolute mode we use a constant pool load.
     SDValue PoolAddr;
     PoolAddr = DAG.getNode(AArch64ISD::WrapperSmall, dl, PtrVT,
                            DAG.getTargetConstantPool(GV, PtrVT, 0, 0,
diff --git a/test/CodeGen/AArch64/extern-weak.ll b/test/CodeGen/AArch64/extern-weak.ll
index f358243bc6f..3d3d8676818 100644
--- a/test/CodeGen/AArch64/extern-weak.ll
+++ b/test/CodeGen/AArch64/extern-weak.ll
@@ -24,4 +24,12 @@ define i32* @bar() {
 ; CHECK: ldr [[BASE:x[0-9]+]], [{{x[0-9]+}}, #:lo12:.LCPI1_0]
 ; CHECK: add x0, [[BASE]], #20
   ret i32* %addr
+}
+
+@defined_weak_var = internal unnamed_addr global i32 0
+
+define i32* @wibble() {
+  ret i32* @defined_weak_var
+; CHECK: adrp [[BASE:x[0-9]+]], defined_weak_var
+; CHECK: add x0, [[BASE]], #:lo12:defined_weak_var
 }
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