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 fa9dcbfc21f9b3f52b2b1b8a20bdda31794bbdd8..34cc0e3b3b84385f2e565e254a9fb1905fa445a1 100644 (file)
--- 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 f358243bc6ff25edb5fb0d33dd5398aceb46c825..3d3d8676818a0012bbe08a06d720066605993cc7 100644 (file)
--- 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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