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Fix signed wrap.

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This commit is contained in:
chriseth
2023-04-15 19:43:48 +02:00
parent ae43c4a705
commit c821dd1c2d
1 changed files with 4 additions and 4 deletions
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8
src/riscv/compiler.rs
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@@ -305,6 +305,8 @@ pil{
// Wraps a value in Y to 32 bits.
// Requires 0 <= Y < 2**33
instr wrap Y -> X { Y = X + wrap_bit * 2**32, X = X_b1 + X_b2 * 0x100 + X_b3 * 0x10000 + X_b4 * 0x1000000 }
// Requires -2**32 <= Y < 2**32
instr wrap_signed Y -> X { Y = X - wrap_bit * 2**32, X = X_b1 + X_b2 * 0x100 + X_b3 * 0x10000 + X_b4 * 0x1000000 }
pil{
col fixed bytes(i) { i & 0xff };
col witness X_b1;
@@ -657,13 +659,11 @@ fn process_instruction(instr: &str, args: &[Argument]) -> String {
}
"sub" => {
let (rd, r1, r2) = rrr(args);
// TODO this cannot use wrap (in case of underflow)
format!("{rd} <=X= wrap({r1} - {r2});\n")
format!("{rd} <=X= wrap_signed({r1} - {r2});\n")
}
"neg" => {
let (rd, r1) = rr(args);
// TODO this cannot use wrap (in case of underflow)
format!("{rd} <=X= wrap(0 - {r1});\n")
format!("{rd} <=X= wrap_signed(0 - {r1});\n")
}
"mul" => {
let (rd, r1, r2) = rrr(args);