Merge pull request #118 from compnerd/arm-unbounded

ARM: handle checking aliases with out-of-bounds GEPs

Author: compnerd

lib/Target/ARM/ARMISelLowering.cpp

@@ -3184,9 +3184,11 @@ static SDValue promoteToConstantPool(const GlobalValue *GV, SelectionDAG &DAG,
 
 bool ARMTargetLowering::isReadOnly(const GlobalValue *GV) const {
   if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
-    GV = GA->getBaseObject();
-  return (isa<GlobalVariable>(GV) && cast<GlobalVariable>(GV)->isConstant()) ||
-         isa<Function>(GV);
+    if (!(GV = GA->getBaseObject()))
+      return false;
+  if (const auto *V = dyn_cast<GlobalVariable>(GV))
+    return V->isConstant();
+  return isa<Function>(GV);
 }
 
 SDValue ARMTargetLowering::LowerGlobalAddress(SDValue Op,

test/CodeGen/ARM/readonly-aliases.ll

@@ -0,0 +1,17 @@
+; RUN: llc -mtriple thumbv7-unknown-linux-android -filetype asm -o - %s | FileCheck %s
+
+@a = protected constant <{ i32, i32 }> <{ i32 0, i32 0 }>
+@b = protected alias i32, getelementptr(i32, i32* getelementptr inbounds (<{ i32, i32 }>, <{ i32, i32 }>* @a, i32 0, i32 1), i32 -1)
+
+declare void @f(i32*)
+
+define void @g() {
+entry:
+  call void @f(i32* @b)
+  ret void
+}
+
+; CHECK-LABEL: g:
+; CHECK: movw [[REGISTER:r[0-9]+]], :lower16:b
+; CHECK: movt [[REGISTER]], :upper16:b
+