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Simplify trap_if_not_representable_as_int.

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Fix typo in function name. Use two fcmp instructions instead of unpacking the bits of the IEEE float and using integer arithmetic to determine details about its value.
This commit is contained in:
Nick Lewycky 2019-07-11 16:24:09 -07:00
parent 7045030532
commit 7fb88251d4
1 changed files with 28 additions and 93 deletions
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121
lib/llvm-backend/src/code.rs
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@ -60,102 +60,37 @@ fn type_to_llvm(intrinsics: &Intrinsics, ty: Type) -> BasicTypeEnum {
}
}
fn trap_if_not_representatable_as_int(
fn trap_if_not_representable_as_int(
builder: &Builder,
intrinsics: &Intrinsics,
context: &Context,
function: &FunctionValue,
lower_bounds: f64,
lower_bound: f64,
upper_bound: f64,
value: FloatValue,
) {
enum FloatSize {
Bits32,
Bits64,
}
let float_ty = value.get_type();
let lower_bound = float_ty.const_float(lower_bound);
let upper_bound = float_ty.const_float(upper_bound);
// The 'U' in the float predicate is short for "unordered" which means that
// the comparison will compare true if either operand is a NaN. Thus, NaNs
// are out of bounds.
let above_upper_bound_cmp =
builder.build_float_compare(FloatPredicate::UGT, value, upper_bound, "above_upper_bound");
let below_lower_bound_cmp =
builder.build_float_compare(FloatPredicate::ULT, value, lower_bound, "below_lower_bound");
let out_of_bounds = builder.build_or(
above_upper_bound_cmp,
below_lower_bound_cmp,
"out_of_bounds",
);
let failure_block = context.append_basic_block(function, "conversion_failure_block");
let continue_block = context.append_basic_block(function, "conversion_success_block");
let float_ty = value.get_type();
let (int_ty, float_size) = if float_ty == intrinsics.f32_ty {
(intrinsics.i32_ty, FloatSize::Bits32)
} else if float_ty == intrinsics.f64_ty {
(intrinsics.i64_ty, FloatSize::Bits64)
} else {
unreachable!()
};
let (exponent, invalid_exponent) = {
let float_bits = builder
.build_bitcast(value, int_ty, "float_bits")
.into_int_value();
let (shift_amount, exponent_mask, invalid_exponent) = match float_size {
FloatSize::Bits32 => (23, 0b01111111100000000000000000000000, 0b11111111),
FloatSize::Bits64 => (
52,
0b0111111111110000000000000000000000000000000000000000000000000000,
0b11111111111,
),
};
builder.build_and(
float_bits,
int_ty.const_int(exponent_mask, false),
"masked_bits",
);
(
builder.build_right_shift(
float_bits,
int_ty.const_int(shift_amount, false),
false,
"exponent",
),
invalid_exponent,
)
};
let is_invalid_float = builder.build_or(
builder.build_int_compare(
IntPredicate::EQ,
exponent,
int_ty.const_int(invalid_exponent, false),
"is_not_normal",
),
builder.build_or(
builder.build_float_compare(
FloatPredicate::ULT,
value,
float_ty.const_float(lower_bounds),
"less_than_lower_bounds",
),
builder.build_float_compare(
FloatPredicate::UGT,
value,
float_ty.const_float(upper_bound),
"greater_than_upper_bounds",
),
"float_not_in_bounds",
),
"is_invalid_float",
);
let is_invalid_float = builder
.build_call(
intrinsics.expect_i1,
&[
is_invalid_float.as_basic_value_enum(),
intrinsics.i1_ty.const_int(0, false).as_basic_value_enum(),
],
"is_invalid_float_expect",
)
.try_as_basic_value()
.left()
.unwrap()
.into_int_value();
builder.build_conditional_branch(is_invalid_float, &failure_block, &continue_block);
builder.build_conditional_branch(out_of_bounds, &failure_block, &continue_block);
builder.position_at_end(&failure_block);
builder.build_call(
intrinsics.throw_trap,
@ -1722,7 +1657,7 @@ impl FunctionCodeGenerator<CodegenError> for LLVMFunctionCodeGenerator {
}
Operator::I32TruncSF32 => {
let v1 = state.pop1()?.into_float_value();
trap_if_not_representatable_as_int(
trap_if_not_representable_as_int(
builder,
intrinsics,
context,
@ -1737,7 +1672,7 @@ impl FunctionCodeGenerator<CodegenError> for LLVMFunctionCodeGenerator {
}
Operator::I32TruncSF64 => {
let v1 = state.pop1()?.into_float_value();
trap_if_not_representatable_as_int(
trap_if_not_representable_as_int(
builder,
intrinsics,
context,
@ -1758,7 +1693,7 @@ impl FunctionCodeGenerator<CodegenError> for LLVMFunctionCodeGenerator {
}
Operator::I64TruncSF32 => {
let v1 = state.pop1()?.into_float_value();
trap_if_not_representatable_as_int(
trap_if_not_representable_as_int(
builder,
intrinsics,
context,
@ -1773,7 +1708,7 @@ impl FunctionCodeGenerator<CodegenError> for LLVMFunctionCodeGenerator {
}
Operator::I64TruncSF64 => {
let v1 = state.pop1()?.into_float_value();
trap_if_not_representatable_as_int(
trap_if_not_representable_as_int(
builder,
intrinsics,
context,
@ -1794,7 +1729,7 @@ impl FunctionCodeGenerator<CodegenError> for LLVMFunctionCodeGenerator {
}
Operator::I32TruncUF32 => {
let v1 = state.pop1()?.into_float_value();
trap_if_not_representatable_as_int(
trap_if_not_representable_as_int(
builder,
intrinsics,
context,
@ -1809,7 +1744,7 @@ impl FunctionCodeGenerator<CodegenError> for LLVMFunctionCodeGenerator {
}
Operator::I32TruncUF64 => {
let v1 = state.pop1()?.into_float_value();
trap_if_not_representatable_as_int(
trap_if_not_representable_as_int(
builder,
intrinsics,
context,
@ -1830,7 +1765,7 @@ impl FunctionCodeGenerator<CodegenError> for LLVMFunctionCodeGenerator {
}
Operator::I64TruncUF32 => {
let v1 = state.pop1()?.into_float_value();
trap_if_not_representatable_as_int(
trap_if_not_representable_as_int(
builder,
intrinsics,
context,
@ -1845,7 +1780,7 @@ impl FunctionCodeGenerator<CodegenError> for LLVMFunctionCodeGenerator {
}
Operator::I64TruncUF64 => {
let v1 = state.pop1()?.into_float_value();
trap_if_not_representatable_as_int(
trap_if_not_representable_as_int(
builder,
intrinsics,
context,