ARM: Avoid doing strncmp on libcall name

Check if the default implementation is the aeabi impl directly.
If getLibcallName returned null, this would crash.

Author: arsenm

llvm/lib/Target/ARM/ARMSelectionDAGInfo.cpp

@@ -35,6 +35,19 @@ bool ARMSelectionDAGInfo::isTargetMemoryOpcode(unsigned Opcode) const {
          Opcode <= ARMISD::LAST_MEMORY_OPCODE;
 }
 
+static bool isAEABIFunctionImpl(const TargetLowering &TLI, RTLIB::Libcall LC) {
+  switch (LC) {
+  case RTLIB::MEMCPY:
+    return TLI.getLibcallImpl(LC) == RTLIB::impl___aeabi_memcpy;
+  case RTLIB::MEMMOVE:
+    return TLI.getLibcallImpl(LC) == RTLIB::impl___aeabi_memmove;
+  case RTLIB::MEMSET:
+    return TLI.getLibcallImpl(LC) == RTLIB::impl___aeabi_memset;
+  default:
+    return false;
+  }
+}
+
 // Emit, if possible, a specialized version of the given Libcall. Typically this
 // means selecting the appropriately aligned version, but we also convert memset
 // of 0 into memclr.
@@ -47,7 +60,7 @@ SDValue ARMSelectionDAGInfo::EmitSpecializedLibcall(
 
   // Only use a specialized AEABI function if the default version of this
   // Libcall is an AEABI function.
-  if (std::strncmp(TLI->getLibcallName(LC), "__aeabi", 7) != 0)
+  if (!isAEABIFunctionImpl(*TLI, LC))
     return SDValue();
 
   // Translate RTLIB::Libcall to AEABILibcall. We only do this in order to be