Revert "Revert "ART: Mterp for arm64""

Looks like some of our assemblers disagree on valid arm64 assembly syntax
Force use of clang for art runtime.  In a subsequent CL, will use form
that both gcc and clang accept.

This reverts commit 43f3fb960bce978df699c8a68a972be2a0d0d221.

Change-Id: Ice83072171ab502c43d492e2238b446c4814ea67
diff --git a/runtime/interpreter/mterp/arm64/footer.S b/runtime/interpreter/mterp/arm64/footer.S
new file mode 100644
index 0000000..b360539
--- /dev/null
+++ b/runtime/interpreter/mterp/arm64/footer.S
@@ -0,0 +1,170 @@
+/*
+ * ===========================================================================
+ *  Common subroutines and data
+ * ===========================================================================
+ */
+
+
+/*
+ * We've detected a condition that will result in an exception, but the exception
+ * has not yet been thrown.  Just bail out to the reference interpreter to deal with it.
+ * TUNING: for consistency, we may want to just go ahead and handle these here.
+ */
+#define MTERP_LOGGING 0
+common_errDivideByZero:
+    EXPORT_PC
+#if MTERP_LOGGING
+    mov  x0, xSELF
+    add  x1, xFP, #OFF_FP_SHADOWFRAME
+    bl MterpLogDivideByZeroException
+#endif
+    b MterpCommonFallback
+
+common_errArrayIndex:
+    EXPORT_PC
+#if MTERP_LOGGING
+    mov  x0, xSELF
+    add  x1, xFP, #OFF_FP_SHADOWFRAME
+    bl MterpLogArrayIndexException
+#endif
+    b MterpCommonFallback
+
+common_errNegativeArraySize:
+    EXPORT_PC
+#if MTERP_LOGGING
+    mov  x0, xSELF
+    add  x1, xFP, #OFF_FP_SHADOWFRAME
+    bl MterpLogNegativeArraySizeException
+#endif
+    b MterpCommonFallback
+
+common_errNoSuchMethod:
+    EXPORT_PC
+#if MTERP_LOGGING
+    mov  x0, xSELF
+    add  x1, xFP, #OFF_FP_SHADOWFRAME
+    bl MterpLogNoSuchMethodException
+#endif
+    b MterpCommonFallback
+
+common_errNullObject:
+    EXPORT_PC
+#if MTERP_LOGGING
+    mov  x0, xSELF
+    add  x1, xFP, #OFF_FP_SHADOWFRAME
+    bl MterpLogNullObjectException
+#endif
+    b MterpCommonFallback
+
+common_exceptionThrown:
+    EXPORT_PC
+#if MTERP_LOGGING
+    mov  x0, xSELF
+    add  x1, xFP, #OFF_FP_SHADOWFRAME
+    bl MterpLogExceptionThrownException
+#endif
+    b MterpCommonFallback
+
+MterpSuspendFallback:
+    EXPORT_PC
+#if MTERP_LOGGING
+    mov  x0, xSELF
+    add  x1, xFP, #OFF_FP_SHADOWFRAME
+    ldr  x2, [xSELF, #THREAD_FLAGS_OFFSET]
+    bl MterpLogSuspendFallback
+#endif
+    b MterpCommonFallback
+
+/*
+ * If we're here, something is out of the ordinary.  If there is a pending
+ * exception, handle it.  Otherwise, roll back and retry with the reference
+ * interpreter.
+ */
+MterpPossibleException:
+    ldr     x0, [xSELF, #THREAD_EXCEPTION_OFFSET]
+    cbz     x0, MterpFallback                       // If not, fall back to reference interpreter.
+    /* intentional fallthrough - handle pending exception. */
+/*
+ * On return from a runtime helper routine, we've found a pending exception.
+ * Can we handle it here - or need to bail out to caller?
+ *
+ */
+MterpException:
+    mov     x0, xSELF
+    add     x1, xFP, #OFF_FP_SHADOWFRAME
+    bl      MterpHandleException                    // (self, shadow_frame)
+    cbz     w0, MterpExceptionReturn                // no local catch, back to caller.
+    ldr     x0, [xFP, #OFF_FP_CODE_ITEM]
+    ldr     w1, [xFP, #OFF_FP_DEX_PC]
+    ldr     xIBASE, [xSELF, #THREAD_CURRENT_IBASE_OFFSET]
+    add     xPC, x0, #CODEITEM_INSNS_OFFSET
+    add     xPC, xPC, x1, lsl #1                    // generate new dex_pc_ptr
+    str     xPC, [xFP, #OFF_FP_DEX_PC_PTR]
+    /* resume execution at catch block */
+    FETCH_INST
+    GET_INST_OPCODE ip
+    GOTO_OPCODE ip
+    /* NOTE: no fallthrough */
+
+/*
+ * Check for suspend check request.  Assumes wINST already loaded, xPC advanced and
+ * still needs to get the opcode and branch to it, and flags are in lr.
+ */
+MterpCheckSuspendAndContinue:
+    ldr     xIBASE, [xSELF, #THREAD_CURRENT_IBASE_OFFSET]  // refresh xIBASE
+    ands    w7, w7, #(THREAD_SUSPEND_REQUEST | THREAD_CHECKPOINT_REQUEST)
+    b.ne    check1
+    GET_INST_OPCODE ip                  // extract opcode from wINST
+    GOTO_OPCODE ip                      // jump to next instruction
+check1:
+    EXPORT_PC
+    mov     x0, xSELF
+    bl      MterpSuspendCheck           // (self)
+    GET_INST_OPCODE ip                  // extract opcode from wINST
+    GOTO_OPCODE ip                      // jump to next instruction
+
+/*
+ * Bail out to reference interpreter.
+ */
+MterpFallback:
+    EXPORT_PC
+#if MTERP_LOGGING
+    mov  x0, xSELF
+    add  x1, xFP, #OFF_FP_SHADOWFRAME
+    bl MterpLogFallback
+#endif
+MterpCommonFallback:
+    mov     x0, #0                                  // signal retry with reference interpreter.
+    b       MterpDone
+
+/*
+ * We pushed some registers on the stack in ExecuteMterpImpl, then saved
+ * SP and LR.  Here we restore SP, restore the registers, and then restore
+ * LR to PC.
+ *
+ * On entry:
+ *  uint32_t* xFP  (should still be live, pointer to base of vregs)
+ */
+MterpExceptionReturn:
+    mov     x0, #1                                  // signal return to caller.
+    b MterpDone
+MterpReturn:
+    ldr     x2, [xFP, #OFF_FP_RESULT_REGISTER]
+    ldr     lr, [xSELF, #THREAD_FLAGS_OFFSET]
+    str     x0, [x2]
+    mov     x0, xSELF
+    ands    lr, lr, #(THREAD_SUSPEND_REQUEST | THREAD_CHECKPOINT_REQUEST)
+    b.eq    check2
+    bl      MterpSuspendCheck                       // (self)
+check2:
+    mov     x0, #1                                  // signal return to caller.
+MterpDone:
+    ldp     fp, lr, [sp, #48]
+    ldp     xPC, xFP, [sp, #32]
+    ldp     xSELF, xINST, [sp, #16]
+    ldp     xIBASE, xREFS, [sp], #64
+    ret
+
+    .cfi_endproc
+    .size   ExecuteMterpImpl, .-ExecuteMterpImpl
+