I am getting this error
> clang -std=c99 -c derivative.c -o derivative.a
fatal error: error in backend: Cannot select: intrinsic %llvm.spu.si.sf
when I try to compile this simple C program with Clang
#include <stdio.h>
#include <math.h>
int N = 100;
double H = 0.001;
double PI = 3.14159265;
void derive(double* input, long elements, double* output) {
for (int i = 1; i < elements - 1; i++) {
output[i - 1] = (input[i + 1] - input[i - 1])/ (2 * H);
}
}
int main() {
double f[N];
double f_prime[N - 2];
for (int i = 0; i < N; i++) {
f[i] = sin(i * 2 * PI / (double)N);
}
derive(f, N, f_prime);
for (int i = 0; i < N - 2; i++) {
printf("%f %f\n", i * 2 * PI / (double)N, f_prime[i]);
}
}
I already searched the Internet, but was not (yet) able to find a solution.
When I compile to Bitcode, it compiles but the execution dumps core.
> clang -emit-llvm -c derivative.c -o derivative.bc
> lli derivative.bc
lli: BitcodeReader.cpp:283: llvm::Value* llvm::BitcodeReaderValueList::getValueFwdRef(unsigned int, llvm::Type*): Assertion `(Ty == 0 || Ty == V->getType()) && "Type mismatch in value table!"' failed.
0 lli 0x0000000000c6fb02
1 lli 0x0000000000c6ff93
2 libpthread.so.0 0x00007f304d7dbbd0
3 libc.so.6 0x00007f304ca19037 gsignal + 55
4 libc.so.6 0x00007f304ca1c698 abort + 328
5 libc.so.6 0x00007f304ca11e03
6 libc.so.6 0x00007f304ca11eb2
7 lli 0x000000000052eeb0 llvm::BitcodeReaderValueList::getConstantFwdRef(unsigned int, llvm::Type*) + 0
8 lli 0x0000000000538943 llvm::BitcodeReader::ParseFunctionBody(llvm::Function*) + 10275
9 lli 0x000000000053acb1 llvm::BitcodeReader::Materialize(llvm::GlobalValue*, std::string*) + 241
10 lli 0x0000000000535195 llvm::BitcodeReader::MaterializeModule(llvm::Module*, std::string*) + 85
11 lli 0x0000000000c0a82f llvm::Module::MaterializeAllPermanently(std::string*) + 31
12 lli 0x00000000005360fc llvm::ParseBitcodeFile(llvm::MemoryBuffer*, llvm::LLVMContext&, std::string*) + 44
13 lli 0x00000000004f70b7
14 lli 0x00000000004e74f3 main + 339
15 libc.so.6 0x00007f304ca03ea5 __libc_start_main + 245
16 lli 0x00000000004f0f41
Stack dump:
0. Program arguments: lli derivative.bc
Aborted (core dumped)
Trying llvm-dis on the bc-file yields an almost identical core dump.
EDIT: I tried to find the minimal failing example, and it seems, the problem is defining the array size via the constant.
this fails:
int main() {
int N = 100;
double f[N];
}
this works:
int main() {
double f[100];
}
EDIT2:
Changing int N = 100 to const int N = 100 makes the program compile with Clang.
It makes sense that the variable should be const, but on the other hand, gcc -std=c99 -Wall derivative.c -lm does not complain if it is not const.