[llvm] r176259 - AArch64: be more careful resorting to inefficient addressing for weak vars.

[Tim Northover]

Author: tnorthover
Date: Thu Feb 28 08:36:31 2013
New Revision: 176259

URL: http://llvm.org/viewvc/llvm-project?rev=176259&view=rev
Log:
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.

Modified:
    llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
    llvm/trunk/test/CodeGen/AArch64/extern-weak.ll

Modified: llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp?rev=176259&r1=176258&r2=176259&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp Thu Feb 28 08:36:31 2013
@@ -1852,11 +1852,10 @@ AArch64TargetLowering::LowerGlobalAddres
   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,

Modified: llvm/trunk/test/CodeGen/AArch64/extern-weak.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/extern-weak.ll?rev=176259&r1=176258&r2=176259&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/extern-weak.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/extern-weak.ll Thu Feb 28 08:36:31 2013
@@ -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
+}
+
+ at 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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