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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.

llvm-svn: 176259
This commit is contained in:
Tim Northover 2013-02-28 14:36:31 +00:00
parent b9d4fd210b
commit c3c5c0971d
2 changed files with 12 additions and 5 deletions
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9
llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
View File

@ -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,

8
llvm/test/CodeGen/AArch64/extern-weak.ll
View File

@ -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
}