https://bugs.llvm.org/show_bug.cgi?id=51962
Bug ID: 51962
Summary: Missing constant propagation with "const" functions,
works with "pure" functions
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
int c;
__attribute__((noinline, pure)) int *pure_test(int *b) {
return *b && c ? &c : 0;
}
__attribute__((noinline, const)) int *const_test(int *b) { return b ? &c : 0; }
void escape(int *);
int test_pure() {
int a = 42;
escape(pure_test(&a));
return a; // OK, LLVM: mov eax, 42
}
int test_const() {
int a = 42;
escape(const_test(&a));
return a; // LLVM: mov eax, dword ptr [rsp + 4], GCC can optimize it to mov
eax, 42
}
https://godbolt.org/z/PKEKeEhM4
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