[ARM] Don't convert switches to lookup tables of pointers with ROPI/RWPI

With the ROPI and RWPI relocation models we can't always have pointers
to global data or functions in constant data, so don't try to convert switches
into lookup tables if any value in the lookup table would require a relocation.
We can still safely emit lookup tables of other values, such as simple
constants.

Differential Revision: https://reviews.llvm.org/D24462

llvm-svn: 283530

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.h b/llvm/lib/Target/ARM/ARMTargetTransformInfo.h
index a0ca9e64800..c8b057b6aaf 100644
--- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.h
+++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.h
@@ -128,6 +128,16 @@ public:
   int getInterleavedMemoryOpCost(unsigned Opcode, Type *VecTy, unsigned Factor,
                                  ArrayRef<unsigned> Indices, unsigned Alignment,
                                  unsigned AddressSpace);
+
+  bool shouldBuildLookupTablesForConstant(Constant *C) const {
+    // In the ROPI and RWPI relocation models we can't have pointers to global
+    // variables or functions in constant data, so don't convert switches to
+    // lookup tables if any of the values would need relocation.
+    if (ST->isROPI() || ST->isRWPI())
+      return !C->needsRelocation();
+
+    return true;
+  }
   /// @}
 };