Which arch and abi?

[Sjors]

I'm trying to reproduce the .s files on macOS, using brew install riscv-tools (and without Docker). This requires manually specifying the arch and abi.

I think I got pretty close with:

riscv64-unknown-elf-gcc -march=rv32im -mabi=ilp32  -S multiply_loop.c

(probably don't meed the m extension?)

But there's still a small diff:

diff --git a/examples/multiply_loop.s b/examples/multiply_loop.s
index 29eb694..6059416 100644
--- a/examples/multiply_loop.s
+++ b/examples/multiply_loop.s
@@ -9,7 +9,8 @@
        .type   runcontract, @function
 runcontract:
        addi    sp,sp,-48
-       sw      s0,44(sp)
+       sw      ra,44(sp)
+       sw      s0,40(sp)
        addi    s0,sp,48
        sw      a0,-36(s0)
        sw      zero,-20(s0)
@@ -27,8 +28,10 @@ runcontract:
        ble     a4,a5,.L3
        lw      a5,-36(s0)
        mv      a0,a5
-       lw      s0,44(sp)
+       lw      ra,44(sp)
+       lw      s0,40(sp)
        addi    sp,sp,48
        jr      ra
        .size   runcontract, .-runcontract
-       .ident  "GCC: () 13.2.0"
+       .ident  "GCC: (g04696df09) 14.2.0"
+       .section        .note.GNU-stack,"",@progbits

Maybe that's a result of gcc 14?

But I guess in a "real world" scenario this would lead to incompatible taptrees?

It reminds me of how back in the day (still?) you could upload a piece of Solidity code to Etherscan and if you specified the exact compiler version, it could verify that the binary smart contract matched the source.

[Sjors]

Can make it even shorter by compiling with -O, which figures out that you can just do a single left shift (slli a0,a0,8).

[halseth]

Yes, you have to agree exactly on the resulting binary (ELF) in order to get compatible taptrees. My guess for why we get a diff is because of slightly different GCC versions and arch/abi as you are saying.

I used riscv32-unknown-elf-gcc compiled with --with-arch=rv32ia --with-abi=ilp32 as seen here: https://github.com/halseth/docker-riscv/commit/48adf83a61780d39887ffcbf9a47d99ed4b79c0e

Maybe check what you get using that specified? 😄

[Sjors]

agree exactly on the resulting binary (ELF) in order to get compatible taptrees

Sounds like the perfect use case for a Guix build.

I'll give your config a try.

[Sjors]

-march=rv32ia -mabi=ilp32 makes no difference. So it's probably the newer GCC version.