arch/risc-v32: Implement lazy FPU, GP relaxation, and QEMU automation for GNU port

.gitignore

@@ -4,6 +4,7 @@
 .tmp/
 _deps/
 build/
+build_qemu/
 Debug/
 CMakeFiles/
 CMakeScripts/

cmake/riscv32_gnu.cmake

@@ -7,7 +7,7 @@ if(DEFINED SOFT_FLOAT)
     set(ARCH_FLAGS "-g -march=rv32ima_zicsr -mabi=ilp32 -mcmodel=medany")
     set(CACHE{SOFT_FLOAT} FORCE 1)
 else()
-    set(ARCH_FLAGS "-g -march=rv32gc -mabi=ilp32d -mcmodel=medany")
+    set(ARCH_FLAGS "-g -march=rv32gc -mabi=ilp32d -mcmodel=medany -mrelax")
 endif()
 set(CFLAGS "${ARCH_FLAGS}")
 set(ASFLAGS "${ARCH_FLAGS}")

ports/risc-v32/gnu/CMakeLists.txt

@@ -17,3 +17,7 @@ target_include_directories(${PROJECT_NAME}
     PUBLIC
     ${CMAKE_CURRENT_LIST_DIR}/inc
 )
+
+if(EXISTS ${CMAKE_CURRENT_LIST_DIR}/example_build/qemu_virt/CMakeLists.txt)
+    add_subdirectory(${CMAKE_CURRENT_LIST_DIR}/example_build/qemu_virt)
+endif()

ports/risc-v32/gnu/example_build/qemu_virt/CMakeLists.txt

@@ -0,0 +1,45 @@
+set(QEMU_DEMO_DIR ${CMAKE_CURRENT_LIST_DIR})
+
+add_executable(kernel.elf EXCLUDE_FROM_ALL
+    ${QEMU_DEMO_DIR}/demo_threadx.c
+    ${QEMU_DEMO_DIR}/entry.s
+    ${QEMU_DEMO_DIR}/uart.c
+    ${QEMU_DEMO_DIR}/plic.c
+    ${QEMU_DEMO_DIR}/hwtimer.c
+    ${QEMU_DEMO_DIR}/trap.c
+    ${QEMU_DEMO_DIR}/board.c
+    ${QEMU_DEMO_DIR}/tx_initialize_low_level.S
+)
+
+target_link_libraries(kernel.elf PRIVATE threadx)
+
+target_include_directories(kernel.elf PRIVATE
+    ${CMAKE_SOURCE_DIR}/common/inc
+    ${CMAKE_SOURCE_DIR}/ports/${THREADX_ARCH}/${THREADX_TOOLCHAIN}/inc
+    ${QEMU_DEMO_DIR}
+)
+
+target_link_options(kernel.elf PRIVATE
+    -T${QEMU_DEMO_DIR}/link.lds
+    -nostartfiles
+    -Wl,-Map=kernel.map
+)
+
+# QEMU/GDB functional test runner.  Optional: skipped silently if the
+# host has no Python 3 interpreter on PATH.
+find_package(Python3 COMPONENTS Interpreter)
+if(Python3_FOUND)
+    add_custom_target(check-functional-riscv32
+        COMMAND ${Python3_EXECUTABLE}
+            ${QEMU_DEMO_DIR}/test/azrtos_test_tx_gnu_riscv32_qemu.py
+            --elf $<TARGET_FILE:kernel.elf>
+            --qemu qemu-system-riscv32
+            --gdb gdb
+        DEPENDS kernel.elf
+        WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+        COMMENT "Running RISC-V32 QEMU/GDB functional test runner..."
+    )
+else()
+    message(STATUS
+        "Python3 not found; check-functional-riscv32 target unavailable.")
+endif()

ports/risc-v32/gnu/example_build/qemu_virt/demo_threadx.c

@@ -9,6 +9,7 @@
 #define     DEMO_BYTE_POOL_SIZE     9120
 #define     DEMO_BLOCK_POOL_SIZE    100
 #define     DEMO_QUEUE_SIZE         100
+float           fpu_test_val = 0.0f;
 
 char *_to_str(ULONG val)
 {
@@ -201,7 +202,7 @@ UINT    status;
         thread_0_counter++;
 
         /* Sleep for 10 ticks.  */
-        tx_thread_sleep(10);
+        tx_thread_sleep(1);
 
         /* Set event flag 0 to wakeup thread 5.  */
         status =  tx_event_flags_set(&event_flags_0, 0x1, TX_OR);
@@ -363,6 +364,8 @@ UINT    status;
         if (status != TX_SUCCESS)
             break;
 
+        /* FPU Test */
+        fpu_test_val += 1.1f;
         /* Get the mutex again with suspension.  This shows
            that an owning thread may retrieve the mutex it
            owns multiple times.  */

ports/risc-v32/gnu/example_build/qemu_virt/entry.s

@@ -1,5 +1,5 @@
 
-.section .text
+.section .text.boot, "ax"
 .align 4
 .global _start
 .extern main
@@ -11,7 +11,10 @@ _start:
 	bne  t0, zero, 1f
 	li x1, 0
 	li x2, 0
-	li x3, 0
+.option push
+.option norelax
+	la gp, __global_pointer$        /* x3 = gp; norelax keeps this load absolute */
+.option pop
 	li x4, 0
 	li x5, 0
 	li x6, 0

ports/risc-v32/gnu/example_build/qemu_virt/link.lds

@@ -10,6 +10,7 @@ SECTIONS
   . = 0x80000000;
 
   .text : {
+    KEEP(*(.text.boot))   /* entry.s _start — must be first at 0x80000000 */
     *(.text .text.*)
     . = ALIGN(0x1000);
     PROVIDE(etext = .);
@@ -24,6 +25,9 @@ SECTIONS
 
   .data : {
     . = ALIGN(16);
+    /* Centre __global_pointer$ in the small-data window so the +/-2 KiB
+       reach of GP-relative addressing covers the .sdata/.sbss area. */
+    PROVIDE( __global_pointer$ = . + 0x800 );
     *(.sdata .sdata.*) /* do not need to distinguish this from .data */
     . = ALIGN(16);
     *(.data .data.*)