Support different Hexagon tools versions, possibly independently of the Hexagon SDK.

PiperOrigin-RevId: 329021591
Change-Id: Ia9d9be685fb36ab1a7b96fb3b758edaf7b2e2fff

tensorflow/lite/micro/tools/make/targets/hexagon_makefile.inc

@@ -1,10 +1,19 @@
 # Settings for Hexagon toolchain.
 # REQUIRED:
-#   - Hexagon SDK 3.5 Toolkit (for hexagon-clang++, hexagon-sim).
-#   - HEXAGON_SDK_PREFIX environment variable must be set to location of
+#   - Hexagon SDK 3.5 Toolkit (for qurt, posix libs).
+#     HEXAGON_SDK_ROOT environment variable must be set to location of
 #     Hexagon_SDK/<version>/ on your machine.
+#   - Hexagon Tools root (for hexagon-clang++, hexagon-sim).
+#     The tool folder may be a part of the Hexagon SDK
+#      (e.g. $(HEXAGON_SDK_ROOT)/tools/HEXAGON_Tools) or installed
+#       separately.
+#     HEXAGON_ROOT environment variable must be set to location of
+#     HEXAGON_Tools on your machine.
+#   - HEXAGON_TOOL_VER: The Hexagon tool version (installed under HEXAGON_ROOT).
+#      For example: 8.3.07
 #   - HEXAGON_CPU_VER: The CPU version to use, will cause a compiler exception
-#                  without providing a version. Acceptable values: v55-v67
+#      without providing a version. Valid values may vary depending on tools
+#      version, but generally in the range: v55-v67
 #
 # Unlike other targets, there is not currently a way to automatically download
 # the Hexagon SDK.  For this reason, users are required to manually download
@@ -12,8 +21,16 @@
 ifeq ($(TARGET), hexagon)
   TARGET_ARCH := hexagon
 
-  ifndef HEXAGON_SDK_PREFIX
-    $(error HEXAGON_SDK_PREFIX is undefined)
+  ifndef HEXAGON_SDK_ROOT
+    $(error HEXAGON_SDK_ROOT is undefined)
+  endif
+
+  ifndef HEXAGON_TOOL_VER
+    $(error HEXAGON_TOOL_VER is undefined)
+  endif
+
+  ifndef HEXAGON_ROOT
+    $(error HEXAGON_ROOT is undefined)
   endif
 
   ifndef HEXAGON_CPU_VER
@@ -55,6 +72,7 @@ ifeq ($(TARGET), hexagon)
     -mcpu=$(HEXAGON_CPU_VER) \
     -m$(HEXAGON_CPU_VER)
 
+  export PATH := $(HEXAGON_ROOT)/$(HEXAGON_TOOL_VER)/Tools/bin:$(PATH)
   TARGET_TOOLCHAIN_PREFIX := hexagon-
   CXX_TOOL := clang++
   CC_TOOL := clang
@@ -63,11 +81,11 @@ ifeq ($(TARGET), hexagon)
   CCFLAGS += $(PLATFORM_ARGS)
   LDFLAGS += \
     -Wl,--gc-sections -lhexagon \
-    $(HEXAGON_SDK_PREFIX)/tools/HEXAGON_Tools/8.3.07/Tools/target/hexagon/lib/v66/libstdc++.a
+    $(HEXAGON_ROOT)/$(HEXAGON_TOOL_VER)/Tools/target/hexagon/lib/v66/libstdc++.a
 
   INCLUDES += \
-    -I$(HEXAGON_SDK_PREFIX)/libs/common/qurt/computev66/include/posix \
-    -I$(HEXAGON_SDK_PREFIX)/libs/common/qurt/computev66/include/qurt
+    -I$(HEXAGON_SDK_ROOT)/libs/common/qurt/computev66/include/posix \
+    -I$(HEXAGON_SDK_ROOT)/libs/common/qurt/computev66/include/qurt
 
   TEST_SCRIPT := tensorflow/lite/micro/testing/test_hexagon_binary.sh
 endif