i#5844 Move x86 expand_scatter_gather to its own file

The existing drx_expand_scatter_gather() function is > 2000 lines of
code, including helper functions, and most of it is very x86 specific.

In preparation for writing the AArch64 version of this function, this
commit moves the x86 implementation of drx_expand_scatter_gather() out
of drx.c into its own architecture specific files, and creates dummy
implementations for other architectures.

The behaviour of the function should be unchanged on all platforms.

As we develop the AArch64 version of drx_expand_scatter_gather(), any
parts of the original x86 implementation which are usefull to both can
be pulled out into helper functions which are shared between both
architectures.

Issues: #5844, #5036, #3837

ext/drx/CMakeLists.txt

@@ -42,6 +42,7 @@ set(DynamoRIO_USE_LIBC OFF)
 set(srcs
   drx.c
   drx_buf.c
+  ${ARCH_NAME}/scatter_gather.c
   # add more here
   )
 

ext/drx/aarch64/scatter_gather.c

@@ -0,0 +1,53 @@
+/* **********************************************************
+ * Copyright (c) 2013-2023 Google, Inc.   All rights reserved.
+ * Copyright (c) 2023      Arm Limited.   All rights reserved.
+ * **********************************************************/
+
+/*
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ * * Neither the name of Google, Inc. nor the names of its contributors may be
+ *   used to endorse or promote products derived from this software without
+ *   specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL GOOGLE, INC. OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ */
+
+/* DynamoRio eXtension utilities */
+
+#include "dr_api.h"
+#include "drx.h"
+#include "drmgr.h"
+
+/*****************************************************************************************
+ * drx_expand_scatter_gather()
+ *
+ * The function expands scatter and gather instructions to a sequence of equivalent
+ * scalar operations.
+ */
+bool
+drx_expand_scatter_gather(void *drcontext, instrlist_t *bb, OUT bool *expanded)
+{
+    /* TODO i#3837: add support for AArch64. */
+    if (expanded != NULL)
+        *expanded = false;
+    return drmgr_current_bb_phase(drcontext) == DRMGR_PHASE_APP2APP;
+}

ext/drx/arm/scatter_gather.c

@@ -0,0 +1,54 @@
+/* **********************************************************
+ * Copyright (c) 2013-2023 Google, Inc.   All rights reserved.
+ * Copyright (c) 2023      Arm Limited.   All rights reserved.
+ * **********************************************************/
+
+/*
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ * * Neither the name of Google, Inc. nor the names of its contributors may be
+ *   used to endorse or promote products derived from this software without
+ *   specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL GOOGLE, INC. OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ */
+
+/* DynamoRio eXtension utilities */
+
+#include "dr_api.h"
+#include "drx.h"
+#include "drmgr.h"
+
+/*****************************************************************************************
+ * drx_expand_scatter_gather()
+ *
+ * The function expands scatter and gather instructions to a sequence of equivalent
+ * scalar operations.
+ *
+ * 32-bit Arm does not have any scatter or gather instructions to expand.
+ */
+bool
+drx_expand_scatter_gather(void *drcontext, instrlist_t *bb, OUT bool *expanded)
+{
+    if (expanded != NULL)
+        *expanded = false;
+    return drmgr_current_bb_phase(drcontext) == DRMGR_PHASE_APP2APP;
+}