Fix PR31896.

Address of an alias of a global with offset is incorrectly lowered as an address of the global (i.e. ignoring offset).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295762 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMISelLowering.cpp

@@ -3077,17 +3077,20 @@ static SDValue promoteToConstantPool(const GlobalValue *GV, SelectionDAG &DAG,
   return DAG.getNode(ARMISD::Wrapper, dl, MVT::i32, CPAddr);
 }
 
+static bool isReadOnly(const GlobalValue *GV) {
+  if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
+    GV = GA->getBaseObject();
+  return (isa<GlobalVariable>(GV) && cast<GlobalVariable>(GV)->isConstant()) ||
+         isa<Function>(GV);
+}
+
 SDValue ARMTargetLowering::LowerGlobalAddressELF(SDValue Op,
                                                  SelectionDAG &DAG) const {
   EVT PtrVT = getPointerTy(DAG.getDataLayout());
   SDLoc dl(Op);
   const GlobalValue *GV = cast<GlobalAddressSDNode>(Op)->getGlobal();
   const TargetMachine &TM = getTargetMachine();
-  if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
-    GV = GA->getBaseObject();
-  bool IsRO =
-      (isa<GlobalVariable>(GV) && cast<GlobalVariable>(GV)->isConstant()) ||
-      isa<Function>(GV);
+  bool IsRO = isReadOnly(GV);
 
   // promoteToConstantPool only if not generating XO text section
   if (TM.shouldAssumeDSOLocal(*GV->getParent(), GV) && !Subtarget->genExecuteOnly())

test/CodeGen/ARM/alias_store.ll

@@ -0,0 +1,16 @@
+; RUN: llc < %s -mtriple=arm-linux-gnueabi | FileCheck %s
+
+@X = constant {i8, i8 } { i8 0, i8 0 }
+@XA = alias i8, getelementptr inbounds ({ i8, i8 }, {i8, i8}* @X, i32 0, i32 1)
+
+define void @f(i8** %p) align 2 {
+entry:
+  store i8* @XA, i8 **%p, align 4
+  ret void
+}
+
+; CHECK: f:
+; CHECK: ldr r{{.*}}, [[L:.*]]
+; CHECK: [[L]]:
+; CHECK-NEXT: .long XA
+; CHECK: XA = X+1