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Merge pull request #3658 from rtfeldman/wasm-fix-shiftRightBy

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wasm: Fix shiftRightBy for U8 and U16
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Brian Carroll 2022-07-29 15:22:15 +02:00 • committed by GitHub
commit 94ccfc30a3
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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
View file

@ -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);

3
crates/compiler/test_gen/src/gen_num.rs
View file

@ -2004,11 +2004,9 @@ fn shift_left_by() {
fn shift_right_by() {
// Sign Extended Right Shift
let is_wasm = cfg!(feature = "gen-wasm");
let is_llvm_release_mode = cfg!(feature = "gen-llvm") && !cfg!(debug_assertions);
// FIXME (Brian) Something funny happening with 8-bit binary literals in tests
if !is_wasm {
assert_evals_to!(
"Num.shiftRightBy 2 (Num.toI8 0b1100_0000u8)",
0b1111_0000u8 as i8,
@ -2023,7 +2021,6 @@ fn shift_right_by() {
if !is_llvm_release_mode {
assert_evals_to!("Num.shiftRightBy 12 0b1000_0000u8", 0b1111_1111u8, u8);
}
}
assert_evals_to!("Num.shiftRightBy 0 12", 12, i64);
assert_evals_to!("Num.shiftRightBy 1 12", 6, i64);
assert_evals_to!("Num.shiftRightBy 1 -12", -6, i64);