Implement N32 floating-point regs #78
Merged
Conversation
This file contains hidden or 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
AngheloAlf
reviewed
Feb 25, 2025
Comment on lines
+2052
to
+2055
| if (!n32) { | ||
| // In O32, only even registers can be used as double registers | ||
| assert(reg % 2 == 0); | ||
| } |
There was a problem hiding this comment.
This isn't true, you can use odd registers on o32. That's how doubles are implemented on mips1
Example code from Rocket robot on wheels:
/* B18C 8000A58C 3C018000 */ lui $at, %hi(D_80000630)
/* B190 8000A590 C4210630 */ lwc1 $f1, %lo(D_80000630)($at)
/* B194 8000A594 C4200634 */ lwc1 $f0, %lo(D_80000630 + 0x4)($at)
/* B198 8000A598 4620A083 */ div.d $f2, $f20, $f0
There was a problem hiding this comment.
that code uses $f2, $f20 and $f0 as double registers which are all even. The lwc1 would be handled by wr() above
There was a problem hiding this comment.
Oh, I missed that part. Nice catch
AngheloAlf
approved these changes
Feb 26, 2025
Comment on lines
+2052
to
+2055
| if (!n32) { | ||
| // In O32, only even registers can be used as double registers | ||
| assert(reg % 2 == 0); | ||
| } |
There was a problem hiding this comment.
Oh, I missed that part. Nice catch
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Outdated suggestions cannot be applied.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.
N32 has a full set of 32 FPRs ("FR=1") instead of having odd regs be aliases for the upper halves of even ones. I checked that this PR generates the same code for O32, but the N32 bits are not well-tested because compilers don't do a lot of FP math
And recomp.cpp now has a
--n32flag (similar to--conservative) to analyze N32 code instead of O32