FP Denorm ACT

[jjscheel]

Technical Group

Architecture Test SIG

ratification-pkg

all FP extensions

Technical Liaison

Allen Baum

Task Category

Arch Tests

Task Sub Category

• gcc
• binutils
• gdb
• intrinsics
• Java
• KVM
• ld
• llvm
• Linux kernel
• QEMU
• Spike

Ratification Target

Legacy

Statement of Work (SOW)

Component names:
D,F,Q, Zfh, Zfinx, Zdinx, Zhinx

Requirements:
Add directed test cases for FP ops that generate a normalized result, but also set the underflow flag

Origin
For an obscure IEEE FP reason, it is possible to generate a normalized FP result while still setting the underflow
flag. This is because the underflow is set after rounding – but for some corner cases, two roundings can occur.
This happens when a denormalized number , after rounding, becomes the largest denorm.
When converted to a denorm format, a second rounding (if the result is odd) occurs, which can round up and
overflow for some rounding modes, and it becomes normalized.

Test Details of Required Tests

For each FP op (FADD, FSUB, FMUL, FDIV, FSQRT, FMUL[N][ADD/SUB},
                             FCVT.S.D, FCVT.D.Q, FCVT.H.x
                             (any FPCVT from a longer FP format to a shorter FP format)

Choose operands that result in raw values for each FP format (before any rounding) of
   EXP = -bias, (is 127 for single, 2047 for double, etc)
   SGN= 0 and1
   MANT = all 1s & all1-1 (including hidden bit) for each FP format
   All 4 combinations of guard and sticky bits

Deliverables:
Since the real requirement is generation of an internal rounded result of all 1s, which is not architecturally visible, we can’t write the coverage except to verify the output is either the smallest normalized number or the largest denorm.

• Assembly language tests that meet the TestFormatSpec,
• Coverage models using riscv-ctg YAML formatted schema Acceptance criteria

Acceptance Criteria:

• Tests pass using the riscof framework

Projected timeframe: 3 months

SOW Signoffs: (delete those not needed)

• Task group liaison sign-off
• Development partner sign-off
• ACT SIG sign-off (if ACT work)

Waiver

• Freeze
• Ratification

Pull Request Details

TBD

[jjscheel]

@ptprasanna, please review this SOW and ask any questions here. The text came from @allenjbaum. He will be your primary resource on this item.

We should discuss more in our next meeting.

[jjscheel]

Updated typos in the description section.

[jjscheel]

Comments from @allenjbaum via email:

I'm wondering if we should include a requirement to show that the intermediate result is in the required range (e.g. with a manual calculation). That's pretty easy for most of these on RV32 (with a hex calculator) except divide and sqrt perhaps,
but more difficult with longer word lengths than hex calculators normally support.

Actually, the tricky bit (sic) is to see that guard/round bits have all 4 combinations

[ptprasanna]

@jjscheel and @allenjbaum, Had a detailed discussion with @anuani21 on this, looks like we do have the tests available and running on the given combination. It's just that the underflow flag which we failed to set on fcsr to acknowledge the result is a denorm, is bit of a gap in the development, which is been caught now. @anuani21 is working on it to fix this up.

[jjscheel]

Thanks, @ptprasanna! Please keep working with @allenjbaum and the sig-arch-test group.

[allenjbaum]

Note that the result that is stored is NOT a denorm ! The result at some intermediate stage could be considered to be a denorm, and then rounded up to be normalized, but the denorm flag is still set.

…

On Thu, Nov 2, 2023 at 9:51 PM Prasanna T ***@***.***> wrote: @jjscheel <https://github.com/jjscheel> and @allenjbaum <https://github.com/allenjbaum>, Had a detailed discussion with @anuani21 <https://github.com/anuani21> on this, looks like we do have the tests available and running on the given combination. It's just that the underflow flag which we failed to set on fcsr to acknowledge the result is a denorm, is bit of a gap in the development, which is been caught now. @anuani21 <https://github.com/anuani21> is working on it to fix this up. — Reply to this email directly, view it on GitHub <#36 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHPXVJQZXDCG6SJ3DDSLKDDYCRZ5VAVCNFSM6AAAAAA5J4FNMWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTOOJRHA4TCMZQGQ> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[jjscheel]

@ptprasanna, any chance on an update here?

[anuani21]

@jjscheel Test generated for F,Zfh,Zfinx and Zhinx extensions and the execution is successful.Generated test case will produce a normalized result and also set an underflow flag.

Tests and coverage reports for F,Zfh,Zfinx and Zhinx are placed in the below link
https://gitlab.com/ptprasanna/actreports/-/tree/main/FP_denorm?ref_type=heads

[allenjbaum]

Could you file a PR for this in the appropriate riscv github repo? These should include the actual additional tests (preferably just some new tests, not completely regenerated tests, which are impossible to review) and new coverage files or just point me at the PR if it's already been filed instead of to a gitlab site.

…

On Tue, Nov 28, 2023 at 12:34 AM anuani21 ***@***.***> wrote: @jjscheel <https://github.com/jjscheel> Test generated for F,Zfh,Zfinx and Zhinx extensions and the execution is successful.Generated test case will produce a normalized result and also set an underflow flag. Tests and coverage reports for F,Zfh,Zfinx and Zhinx are placed in the below link https://gitlab.com/ptprasanna/actreports/-/tree/main/FP_denorm?ref_type=heads — Reply to this email directly, view it on GitHub <#36 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHPXVJSJG5XNXH2FYATVA5TYGWO2TAVCNFSM6AAAAAA5J4FNMWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQMRZGMZTKNZYGY> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[anuani21]

@allenjbaum, I am generating test case for D, Zdinx and Q extension for the given combination. Along with the coverage report for these extensions, I will raise a PR in appropriate riscv github.

[allenjbaum]

Thanks. I've been reviewing FP coverage overall, and have some questions about the coverage descriptions in - riscv-isac <https://github.com/riscv-software-src/riscv-isac/tree/master> - /riscv_isac <https://github.com/riscv-software-src/riscv-isac/tree/master/riscv_isac>/ fp_dataset.py Who would the right person to be to answer questions about that?

…

On Sun, Dec 10, 2023 at 10:19 PM anuani21 ***@***.***> wrote: @allenjbaum <https://github.com/allenjbaum>, I am generating test case for D, Zdinx and Q extension for the given combination. Along with the coverage report for these extensions, I will raise a PR in appropriate riscv github. — Reply to this email directly, view it on GitHub <#36 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHPXVJQVIEMONQRSWLBWF7DYI2QVTAVCNFSM6AAAAAA5J4FNMWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQNBZGM4TGOJWGA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[anuani21]

@jjscheel, Test generated for D extensions and the execution is successful.Generated test case will produce a normalized result and also set an underflow flag.

I am generating test case for Zdinx and Q extension for the given combination.Along with coverage report for these extensions, I will a raise a PR in appropriate riscv github.

[allenjbaum]

Are you generating tests for *just* this cover point, or adding the coverpoint(s) to the existing ones and regenerating everything? Generating the test for *just* this coverpoint is preferred, as otherwise it takes a very long time

…

On Mon, Jan 22, 2024 at 8:12 PM anuani21 ***@***.***> wrote: @jjscheel <https://github.com/jjscheel>, Test generated for D extensions and the execution is successful.Generated test case will produce a normalized result and also set an underflow flag. I am generating test case for Zdinx and Q extension for the given combination.Along with coverage report for these extensions, I will a raise a PR in appropriate riscv github. — Reply to this email directly, view it on GitHub <#36 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHPXVJULEVJKSW2626WBUSLYP42BRAVCNFSM6AAAAAA5J4FNMWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSMBVGI3DCMRVG4> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[anuani21]

Hi, I am generating tests for just this coverpoints alone.Not added to the existing tests. For the Q extension alone, I will need to make some changes in the IBM model for introducing flen=128 because in existing one it has a fix only for flen 32 and 64. Regards, Anusha On Tue, Jan 23, 2024 at 11:36 AM Allen Baum ***@***.***> wrote:

…

Are you generating tests for *just* this cover point, or adding the coverpoint(s) to the existing ones and regenerating everything? Generating the test for *just* this coverpoint is preferred, as otherwise it takes a very long time On Mon, Jan 22, 2024 at 8:12 PM anuani21 ***@***.***> wrote: > @jjscheel <https://github.com/jjscheel>, Test generated for D extensions > and the execution is successful.Generated test case will produce a > normalized result and also set an underflow flag. > > I am generating test case for Zdinx and Q extension for the given > combination.Along with coverage report for these extensions, I will a raise > a PR in appropriate riscv github. > > — > Reply to this email directly, view it on GitHub > < #36 (comment)>, > or unsubscribe > < https://github.com/notifications/unsubscribe-auth/AHPXVJULEVJKSW2626WBUSLYP42BRAVCNFSM6AAAAAA5J4FNMWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSMBVGI3DCMRVG4> > . > You are receiving this because you were mentioned.Message ID: > ***@***.***> > — Reply to this email directly, view it on GitHub <#36 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/A3G6FFZI62QYORSTFMD2F7DYP5HPLAVCNFSM6AAAAAA5J4FNMWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSMBVGM2TAMBRGY> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[allenjbaum]

great! I would make Q-extension lower priority than other work though (I assume there is lots of other work!)

…

On Mon, Jan 22, 2024 at 10:49 PM anuani21 ***@***.***> wrote: Hi, I am generating tests for just this coverpoints alone.Not added to the existing tests. For the Q extension alone, I will need to make some changes in the IBM model for introducing flen=128 because in existing one it has a fix only for flen 32 and 64. Regards, Anusha On Tue, Jan 23, 2024 at 11:36 AM Allen Baum ***@***.***> wrote: > Are you generating tests for *just* this cover point, or adding the > coverpoint(s) to the existing ones and regenerating everything? > Generating the test for *just* this coverpoint is preferred, as > otherwise it takes a very long time > > On Mon, Jan 22, 2024 at 8:12 PM anuani21 ***@***.***> wrote: > > > @jjscheel <https://github.com/jjscheel>, Test generated for D > extensions > > and the execution is successful.Generated test case will produce a > > normalized result and also set an underflow flag. > > > > I am generating test case for Zdinx and Q extension for the given > > combination.Along with coverage report for these extensions, I will a > raise > > a PR in appropriate riscv github. > > > > — > > Reply to this email directly, view it on GitHub > > < > #36 (comment)>, > > > or unsubscribe > > < > https://github.com/notifications/unsubscribe-auth/AHPXVJULEVJKSW2626WBUSLYP42BRAVCNFSM6AAAAAA5J4FNMWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSMBVGI3DCMRVG4> > > > . > > You are receiving this because you were mentioned.Message ID: > > ***@***.***> > > > > — > Reply to this email directly, view it on GitHub > < #36 (comment)>, > or unsubscribe > < https://github.com/notifications/unsubscribe-auth/A3G6FFZI62QYORSTFMD2F7DYP5HPLAVCNFSM6AAAAAA5J4FNMWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSMBVGM2TAMBRGY> > . > You are receiving this because you were mentioned.Message ID: > ***@***.***> > — Reply to this email directly, view it on GitHub <#36 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHPXVJTZX2J3S6C3DITTR3LYP5MPLAVCNFSM6AAAAAA5J4FNMWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSMBVGM4DQNBWGQ> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[anuani21]

@jjscheel, Here are the updates from IITM,

Zdinx- Three operand instructions like (fmadd,fmsub,fnmadd,fnmsub) test generated but few coverpoints are not met up.I am fixing this issue.
Q extension- yet to start the test.

[jjscheel]

@anuani21, I have set the state of the project to "Planning". I'd appreciate some outlook as to when the work will be done and confirmation that this is a "Medium" sized project (3-6 months of work).

[anuani21]

No progress made since last Call. Was busy on Debug ACT for Native Triggers.

[anuani21]

No progress made since last Call. Was busy on Debug ACT for Native Triggers.

[anuani21]

No progress made since last Call. Was busy on Debug ACT for Native Triggers.

[jjscheel]

Thanks. Understand.