alexanderFell
commented
7 years ago Okay I tried the whole day, 5 minutes after submitting this issue, I figured it out: It seems, clang didn't know, that I have a multiplier (as suspected), so changing the clang++ invocation like to:
riscv64-unknown-linux-gnu-clang++ --sysroot=../../sysroot/ multiplier.cpp -S -mriscv=RV64IAM -o multiplier.S
did the trick. Sorry for the noise created.
byllgrim
Hey all, I am hoping, someone can point me out what I am doing wrong. I would like to compile the following program:
include
int main(int argc, char* argv) { short a = atoi(argv[1]); short b = atoi(argv[2]); return a b; }
I am trying to compile it and it results in riscv64-unknown-linux-gnu-clang++ --sysroot=../../sysroot/ multiplier.cpp -S -o multiplier.S riscv64-unknown-linux-gnu-g++ multiplier.S -o multiplier.riscv --static /tmp/ccLOnAlk.o: In function 'main': multiplier.cpp:(.text+0x68): undefined reference to '__mulsi3' collect2: error: ld returned 1 exit status Makefile:26: recipe for target 'multiplier.riscv' failed make: *** [multiplier.riscv] Error 1
multiplier.S: .text .file "multiplier1.cpp" .globl main .p2align 2 .type main,@function main: addi x2, x2, -64 sd x1, 56(x2) sd x8, 48(x2) add x8, x2, x0 addiw x5, x10, 0 addi x10, x11, 0 sw x0, 44(x8) sw x5, 40(x8) sd x11, 32(x8) ld x11, 8(x11) lui x6, %hi(atoi) addi x6, x6, %lo(atoi) sd x10, 16(x8) addi x10, x11, 0 sd x6, 8(x8) jalr x1, x6, 0 sh x10, 30(x8) ld x6, 32(x8) ld x10, 16(x6) ld x6, 8(x8) jalr x1, x6, 0 sh x10, 28(x8) lh x5, 30(x8) lh x7, 28(x8) addiw x10, x5, 0 addiw x11, x7, 0 jal x1, __mulsi3 add x2, x8, x0 ld x8, 48(x2) ld x1, 56(x2) addi x2, x2, 64 ret Lfunc_end0: .size main, Lfunc_end0-main
The issue here is the mulsi3 call, which seems to be missing in the following riscv toolchain. If I change the type of a and b to long (anything with a word size that is larger than int) mulsi3 is replaced by __muldi3, which is defined by the RISCV toolchain and consists of a software multiplication.
I am pretty sure I made a mistake and I forgot a flag somewhere telling clang to use a hardware multiplier (mul, mulw,...), but I have no idea, what the flag should look like (I am new to llvm and riscv). I saw in RISCVInstrInfoM.td that it requires "HasM" but I do not know, where to put it.
Thanks a lot in advance, Alex