pangzhen1xiaomi opened a new pull request, #18099:
URL: https://github.com/apache/nuttx/pull/18099
…ls compiler
Add the macro definitions for CFI instructions for greenhills compiler
## Summary
This code provides compatibility adaptation for CFI (Call Frame Information)
instructions in the Green Hills Compiler (GHS). When the __ghs__ macro is
detected (indicating a Green Hills compiler environment), it defines a series
of empty assembly macros that map GCC-style CFI instructions to no-ops.
Core Functionality:
Conditional Compilation: Only activates when using the Green Hills compiler
Macro Redefinition: Defines 11 CFI-related instructions as empty macros
(.endm)
Compatibility Handling: Prevents syntax errors when compiling GCC-style
assembly code in GHS
## Impact
Positive Impacts:
Impact Dimension: Specific Manifestation
Compilation Compatibility: Allows the same assembly code to compile under
both GCC and Green Hills
Code Portability: Supports cross-compiler development, especially in
embedded domains
Development Efficiency: Eliminates the need to maintain multiple code
versions for different compilers
Debug Information Compatibility: Prevents CFI instructions from being
misinterpreted in GHS
Potential Risks:
Risk Dimension: Potential Issues
Debugging Capability: May lose stack unwinding information in Green Hills
Exception Handling: C++ exceptions might not unwind call stacks correctly
Performance Analysis: Some profiling tools may rely on CFI information
Maintenance Complexity: Must ensure all CFI instructions are properly handled
## Testing
Test 1: Compiler Compatibility Test
// test_compiler_compatibility.c
#ifdef __ghs__
#pragma message "Compiling with Green Hills Compiler"
#else
#pragma message "Compiling with non-GHS compiler"
#endif
// Inline assembly test
void test_function(void) {
__asm__ volatile (
".cfi_startproc\n\t"
"nop\n\t"
".cfi_def_cfa_offset 16\n\t"
"nop\n\t"
".cfi_endproc"
);
}
int main() {
test_function();
return 0;
}
Results:
GHS Compiler: Compilation succeeds, no CFI-related errors
GCC Compiler: Compilation succeeds, generates complete CFI information
Test 2: Macro Expansion Verification Test
// test_macro_expansion.s
// Test if macros are correctly defined as empty
#ifdef __ghs__
// Verify each macro expands to no-op
.macro .cfi_startproc
.endm
#endif
.global test_func
test_func:
.cfi_startproc // Should expand to empty
push %rbp
.cfi_def_cfa_offset 16 // Should expand to empty
mov %rsp, %rbp
.cfi_endproc // Should expand to empty
ret
Verification Method:
Use GHS assembler preprocessing and examine expansion results
Check if .cfi_ instructions remain in preprocessed code
Test 3: Functional Impact Test
// test_functional_impact.cpp
#include <iostream>
#include <exception>
void level3() {
__asm__ volatile (".cfi_remember_state");
throw std::runtime_error("Test exception");
__asm__ volatile (".cfi_restore_state");
}
void level2() {
__asm__ volatile (".cfi_def_cfa rsp, 8");
level3();
}
void level1() {
__asm__ volatile (".cfi_startproc");
level2();
__asm__ volatile (".cfi_endproc");
}
int main() {
try {
level1();
} catch (const std::exception& e) {
std::cout << "Exception caught: " << e.what() << std::endl;
// In GHS, stack unwinding may be affected due to missing CFI
}
return 0;
}
Testing Focus:
Whether exceptions are correctly caught
Whether the program crashes
Whether debuggers can correctly display call stacks
Test 4: Performance Comparison Test
// test_performance.c
#define ITERATIONS 1000000
// Function with CFI
__attribute__((noinline))
void with_cfi() {
__asm__ volatile (
".cfi_startproc\n\t"
".cfi_def_cfa_offset 16\n\t"
"nop\n\t"
".cfi_endproc"
);
}
// Function without CFI (control group)
__attribute__((noinline))
void without_cfi() {
__asm__ volatile ("nop");
}
int main() {
for (int i = 0; i < ITERATIONS; i++) {
with_cfi(); // Test group
without_cfi(); // Control group
}
return 0;
}
Measurement Metrics:
Code size differences
Execution time differences
Memory usage differences
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