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wasm: Fix shiftRightBy for U8 and U16

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Brian Carroll 2022-07-29 14:05:08 +02:00
parent 01eb161ffe
commit 0041d4f3bc
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2 changed files with 52 additions and 22 deletions
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47
crates/compiler/gen_wasm/src/low_level.rs
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@ -1610,13 +1610,46 @@ impl<'a> LowLevelCall<'a> {
}
}
NumShiftRightBy => {
backend.storage.load_symbols(
&mut backend.code_builder,
&[self.arguments[1], self.arguments[0]],
);
let bits = self.arguments[0];
let num = self.arguments[1];
match CodeGenNumType::from(self.ret_layout) {
I32 => backend.code_builder.i32_shr_s(),
I64 => backend.code_builder.i64_shr_s(),
I32 => {
// In most languages this operation is for signed numbers, but Roc defines it on all integers.
// So the argument is implicitly converted to signed before the shift operator.
// We need to make that conversion explicit for i8 and i16, which use Wasm's i32 type.
let bit_width = 8 * self.ret_layout.stack_size(TARGET_INFO) as i32;
if bit_width < 32 && !symbol_is_signed_int(backend, num) {
// Sign-extend the number by shifting left and right again
backend
.storage
.load_symbols(&mut backend.code_builder, &[num]);
backend.code_builder.i32_const(32 - bit_width);
backend.code_builder.i32_shl();
backend.code_builder.i32_const(32 - bit_width);
backend.code_builder.i32_shr_s();
backend
.storage
.load_symbols(&mut backend.code_builder, &[bits]);
// Do the actual bitshift operation
backend.code_builder.i32_shr_s();
// Restore to unsigned
backend.code_builder.i32_const((1 << bit_width) - 1);
backend.code_builder.i32_and();
} else {
backend
.storage
.load_symbols(&mut backend.code_builder, &[num, bits]);
backend.code_builder.i32_shr_s();
}
}
I64 => {
backend
.storage
.load_symbols(&mut backend.code_builder, &[num, bits]);
backend.code_builder.i64_shr_s();
}
I128 => todo!("{:?} for I128", self.lowlevel),
_ => panic_ret_type(),
}
@ -1624,7 +1657,7 @@ impl<'a> LowLevelCall<'a> {
NumShiftRightZfBy => {
match CodeGenNumType::from(self.ret_layout) {
I32 => {
// This is normally an unsigned operation, but Roc defines it on all integer types.
// In most languages this operation is for unsigned numbers, but Roc defines it on all integers.
// So the argument is implicitly converted to unsigned before the shift operator.
// We need to make that conversion explicit for i8 and i16, which use Wasm's i32 type.
let bit_width = 8 * self.ret_layout.stack_size(TARGET_INFO);