Fix invalid codegen on small to long int cast #1921
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
dcodeIO
commented
Jun 23, 2021
Comment on lines
+1355
to
+1360
| // sign extensions overflow if result can have high garbage bits in the target type | ||
| case UnaryOp.Extend8I32: return type.size < (type.isUnsignedIntegerValue ? 32 : 8); | ||
| case UnaryOp.Extend8I64: return type.size < (type.isUnsignedIntegerValue ? 64 : 8); | ||
| case UnaryOp.Extend16I32: return type.size < (type.isUnsignedIntegerValue ? 32 : 16); | ||
| case UnaryOp.Extend16I64: return type.size < (type.isUnsignedIntegerValue ? 64 : 16); | ||
| case UnaryOp.Extend32I64: return type.size < (type.isUnsignedIntegerValue ? 64 : 32); |
There was a problem hiding this comment.
Perhaps a comment here for review, by example of i32.extend16_s:
If the target type is unsigned, an i32.extend16_s can yield high garbage bits if the target type is smaller than u32. u32 naturally does not care about garbage bits, but any smaller unsigned integer could have garbage high 1s after the instruction.
If the target type is signed, an i32.extend16_s can yield high garbage 0s after leading 1s if the target type is smaller than i16. If the target type is i16 or larger, the instruction would set all high bits to either 0 or 1, which makes the value valid regardless.
MaxGraey
approved these changes
Jun 24, 2021
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
fixes #1911