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

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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
This commit is contained in:
Tim Northover 2013-02-28 14:36:31 +00:00
parent 5366ab21f4
commit 6ff20f205b
2 changed files with 12 additions and 5 deletions
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9
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
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
}