Move SVE length check to a veneer (#502)

Author: solidpixel

Source/astcenccli_entry.cpp

@@ -18,22 +18,23 @@
 /**
  * @brief Application entry point.
  *
- * This module contains the command line entry point which also performs the
- * role of validating the host extended ISA support meets the needs of the
- * tools.
+ * This module contains the first command line entry point veneer, used to
+ * validate that the host extended ISA availability matches the tool build.
+ * It is compiled without any extended ISA support so it's guaranteed to be
+ * executable without any invalid instruction errors.
  */
 
 #include <cstdio>
 
 /**
- * @brief The main entry point.
+ * @brief The main veneer entry point.
  *
  * @param argc   The number of arguments.
  * @param argv   The vector of arguments.
  *
  * @return 0 on success, non-zero otherwise.
  */
-int astcenc_main(
+int astcenc_main_veneer(
 	int argc,
 	char **argv);
 
@@ -311,5 +312,5 @@ int main(
 		return 1;
 	}
 
-	return astcenc_main(argc, argv);
+	return astcenc_main_veneer(argc, argv);
 }

Source/astcenccli_entry2.cpp

@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: Apache-2.0
+// ----------------------------------------------------------------------------
+// Copyright 2024 Arm Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy
+// of the License at:
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations
+// under the License.
+// ----------------------------------------------------------------------------
+
+/**
+ * @brief Application entry point second veneer.
+ *
+ * This module contains the second command line entry point veneer, used to
+ * validate that Arm SVE vector width matches the tool build. When used, it is
+ * compiled with SVE ISA support but without any vector legnth override, so it
+ * will see the native SVE vector length exposed to the application.
+ */
+
+#include <cstdio>
+
+#if ASTCENC_SVE != 0
+	#include <arm_sve.h>
+#endif
+
+/**
+ * @brief The main entry point.
+ *
+ * @param argc   The number of arguments.
+ * @param argv   The vector of arguments.
+ *
+ * @return 0 on success, non-zero otherwise.
+ */
+int astcenc_main(
+	int argc,
+	char **argv);
+
+/**
+ * @brief Print a formatted string to stderr.
+ */
+template<typename ... _Args>
+static inline void print_error(
+	const char* format,
+	_Args...args
+) {
+	fprintf(stderr, format, args...);
+}
+
+int astcenc_main_veneer(
+	int argc,
+	char **argv
+) {
+#if ASTCENC_SVE != 0
+	// svcntw() return compile-time length if used with -msve-vector-bits
+	if (svcntw() != ASTCENC_SVE)
+	{
+		int bits = ASTCENC_SVE * 32;
+		print_error("ERROR: Host SVE support is not a %u-bit implementation\n", bits);
+		return 1;
+	}
+#endif
+
+	return astcenc_main(argc, argv);
+}

Source/astcenccli_toplevel.cpp

@@ -1889,25 +1889,12 @@ static void print_diagnostic_images(
  *
  * @return 0 on success, non-zero otherwise.
  */
-int
-astcenc_main(
+int astcenc_main(
 	int argc,
 	char **argv
 ) {
 	set_thread_name("astc main");
 
-#if ASTCENC_SVE != 0
-	// Do this check here because is needs SVE instructions so cannot be in
-	// the veneer check which is compiled as stock Armv8. We know we have SVE
-	// by the time we get this far, but not the vector width.
-	if (svcntw() != ASTCENC_SVE)
-	{
-		uint32_t bits = ASTCENC_SVE * 32;
-		print_error("ERROR: Host does not implement %u bit SVE ISA extension\n", bits);
-		return false;
-	}
-#endif
-
 	double start_time = get_time();
 
 	if (argc < 2)

Source/cmake_core.cmake

@@ -1,6 +1,6 @@
 #  SPDX-License-Identifier: Apache-2.0
 #  ----------------------------------------------------------------------------
-#  Copyright 2020-2023 Arm Limited
+#  Copyright 2020-2024 Arm Limited
 #
 #  Licensed under the Apache License, Version 2.0 (the "License"); you may not
 #  use this file except in compliance with the License. You may obtain a copy
@@ -105,9 +105,14 @@ endif()
 if(${ASTCENC_CLI})
     # Veneer is compiled without any extended ISA so we can safely do
     # ISA compatability checks without triggering a SIGILL
-    add_library(${ASTCENC_TARGET}-veneer
+    add_library(${ASTCENC_TARGET}-veneer1
         astcenccli_entry.cpp)
 
+    # Veneer is compiled with extended ISA but without vector length overrides
+    # so we can safely do SVE vector length compatability checks
+    add_library(${ASTCENC_TARGET}-veneer2
+        astcenccli_entry2.cpp)
+
     add_executable(${ASTCENC_TARGET}
         astcenccli_error_metrics.cpp
         astcenccli_image.cpp
@@ -119,11 +124,12 @@ if(${ASTCENC_CLI})
 
     target_link_libraries(${ASTCENC_TARGET}
         PRIVATE
-            ${ASTCENC_TARGET}-veneer
+            ${ASTCENC_TARGET}-veneer1
+            ${ASTCENC_TARGET}-veneer2
             ${ASTCENC_TARGET}-static)
 endif()
 
-macro(astcenc_set_properties ASTCENC_TARGET_NAME ASTCENC_IS_VENEER)
+macro(astcenc_set_properties ASTCENC_TARGET_NAME ASTCENC_VENEER_TYPE)
 
     target_compile_features(${ASTCENC_TARGET_NAME}
         PRIVATE
@@ -306,11 +312,17 @@ macro(astcenc_set_properties ASTCENC_TARGET_NAME ASTCENC_IS_VENEER)
                 ASTCENC_POPCNT=0
                 ASTCENC_F16C=0)
 
-        # Enable SVE
-        if (NOT ${ASTCENC_IS_VENEER})
+        # Enable SVE in the core library
+        if (NOT ${ASTCENC_VENEER_TYPE})
             target_compile_options(${ASTCENC_TARGET_NAME}
                 PRIVATE
                     -march=armv8-a+sve -msve-vector-bits=256)
+
+        # Enable SVE without fixed vector length in the veneer
+        elseif (${ASTCENC_VENEER_TYPE} EQUAL 2)
+            target_compile_options(${ASTCENC_TARGET_NAME}
+                PRIVATE
+                    -march=armv8-a+sve)
         endif()
 
     elseif(${ASTCENC_ISA_SIMD} MATCHES "sse2")
@@ -341,7 +353,7 @@ macro(astcenc_set_properties ASTCENC_TARGET_NAME ASTCENC_IS_VENEER)
                 ASTCENC_POPCNT=1
                 ASTCENC_F16C=0)
 
-        if (${ASTCENC_IS_VENEER})
+        if (${ASTCENC_VENEER_TYPE} GREATER 0)
             # Force SSE2 on AppleClang (normally SSE4.1 is the default)
             target_compile_options(${ASTCENC_TARGET_NAME}
                 PRIVATE
@@ -366,7 +378,7 @@ macro(astcenc_set_properties ASTCENC_TARGET_NAME ASTCENC_IS_VENEER)
                 ASTCENC_POPCNT=1
                 ASTCENC_F16C=1)
 
-        if (${ASTCENC_IS_VENEER})
+        if (${ASTCENC_VENEER_TYPE} GREATER 0)
             # Force SSE2 on AppleClang (normally SSE4.1 is the default)
             target_compile_options(${ASTCENC_TARGET_NAME}
                 PRIVATE
@@ -388,7 +400,7 @@ macro(astcenc_set_properties ASTCENC_TARGET_NAME ASTCENC_IS_VENEER)
         # which significantly improve performance. Note that this DOES reduce
         # image quality by up to 0.2 dB (normally much less), but buys an
         # average of 10-15% performance improvement ...
-        if((NOT ${ASTCENC_INVARIANCE}) AND (NOT ${ASTCENC_IS_VENEER}))
+        if((NOT ${ASTCENC_INVARIANCE}) AND (NOT ${ASTCENC_VENEER_TYPE}))
             target_compile_options(${ASTCENC_TARGET_NAME}
                 PRIVATE
                     $<${is_gnu_fe}:-mfma>)
@@ -447,14 +459,19 @@ if(${ASTCENC_SHAREDLIB})
 endif()
 
 if(${ASTCENC_CLI})
-    astcenc_set_properties(${ASTCENC_TARGET}-veneer ON)
-    astcenc_set_properties(${ASTCENC_TARGET} OFF)
+    astcenc_set_properties(${ASTCENC_TARGET}-veneer1 1)
+    astcenc_set_properties(${ASTCENC_TARGET}-veneer2 2)
+    astcenc_set_properties(${ASTCENC_TARGET} 0)
 
-    target_compile_options(${ASTCENC_TARGET}
+    target_compile_options(${ASTCENC_TARGET}-veneer1
         PRIVATE
             $<${is_msvc_fe}:/W3>)
 
-    target_compile_options(${ASTCENC_TARGET}-veneer
+    target_compile_options(${ASTCENC_TARGET}-veneer2
+        PRIVATE
+            $<${is_msvc_fe}:/W3>)
+
+    target_compile_options(${ASTCENC_TARGET}
         PRIVATE
             $<${is_msvc_fe}:/W3>)