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Add support for Zhinxmin extension #753

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Add support for Zhinxmin extension #753

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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -99,7 +99,7 @@ For booting operating system images, see the information under the
- F and D extensions for single and double-precision floating-point, v2.2
- Zfh and Zfhmin extensions for half-precision floating-point, v1.0
- Zfa extension for additional floating-point instructions, v1.0
- Zfinx, Zdinx, and Zhinx extensions for floating-point in integer registers, v1.0
- Zfinx, Zdinx, Zhinx, and Zhinxmin extensions for floating-point in integer registers, v1.0
- C extension for compressed instructions, v2.0
- Zca, Zcf, Zcd, and Zcb extensions for code size reduction, v1.0
- Zcmop extension for compressed May-Be-Operations, v1.0
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3 changes: 3 additions & 0 deletions config/default.json
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Expand Up @@ -169,6 +169,9 @@
"Zhinx": {
"supported": false
},
"Zhinxmin": {
"supported": false
},
"Zvbb": {
"supported": true
},
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3 changes: 3 additions & 0 deletions model/riscv_extensions.sail
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Expand Up @@ -169,6 +169,9 @@ function clause hartSupports(Ext_Zksh) = config extensions.Zksh.supported
// Floating-Point in Integer Registers (half precision)
enum clause extension = Ext_Zhinx
function clause hartSupports(Ext_Zhinx) = config extensions.Zhinx.supported
// Floating-Point in Integer Registers (minimal half precision)
enum clause extension = Ext_Zhinxmin
function clause hartSupports(Ext_Zhinxmin) = config extensions.Zhinxmin.supported

// Vector Basic Bit-manipulation
enum clause extension = Ext_Zvbb
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3 changes: 2 additions & 1 deletion model/riscv_insts_zfh.sail
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Expand Up @@ -7,6 +7,7 @@
/*=======================================================================================*/

function clause currentlyEnabled(Ext_Zhinx) = hartSupports(Ext_Zhinx) & currentlyEnabled(Ext_Zfinx)
function clause currentlyEnabled(Ext_Zhinxmin) = (hartSupports(Ext_Zhinxmin) & currentlyEnabled(Ext_Zfinx))| currentlyEnabled(Ext_Zhinx)
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Suggested change
function clause currentlyEnabled(Ext_Zhinxmin) = (hartSupports(Ext_Zhinxmin) & currentlyEnabled(Ext_Zfinx))| currentlyEnabled(Ext_Zhinx)
function clause currentlyEnabled(Ext_Zhinxmin) = (hartSupports(Ext_Zhinxmin) & currentlyEnabled(Ext_Zfinx))

I looked through the specification but couldn’t find anything indicating that Zhinx enables Zhinxmin.

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This is the same approach we took for Zfh and Zfhmin. Zhinx includes everything in Zhinxmin, so we gate the relevant instructions on Zhinxmin and enable Zhinxmin if Zhinx is enabled.

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Hmm, I don't know if this is a good approach to turn on extensions silently. Whats the advantage of enabling Zhinxmin automatically when Zhinx is active, given that Zhinx already includes all those instructions? Wouldn't it be cleaner to keep each extension's enabled status independent?

This may be confusing for the reader.

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There's been a lot of discussion surrounding these extensions where one implies another. See riscv/riscv-isa-manual#1121 and riscv/riscv-isa-manual#869 for a discussion about M/Zmmul. Right now, we do this for a number of other extensions (Zfhmin, Zmmul, possibly a few others), so I'd be in favor of keeping it consistent in this PR and we can open an issue to potentially change all of them later.

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Yeah I agree, lets keep it and handle this in a separate PR.


/* **************************************************************** */
/* This file specifies the instructions in the Zfh extension */
Expand Down Expand Up @@ -167,7 +168,7 @@ function fle_H (v1, v2, is_quiet) = {
function haveHalfFPU() -> bool = currentlyEnabled(Ext_Zfh) | currentlyEnabled(Ext_Zhinx)
// Support for conversion of halves to/from single & double, but no actual
// calculations with halves.
function haveHalfMin() -> bool = haveHalfFPU() | currentlyEnabled(Ext_Zfhmin)
function haveHalfMin() -> bool = haveHalfFPU() | currentlyEnabled(Ext_Zfhmin) | currentlyEnabled(Ext_Zhinxmin)

/* ****************************************************************** */
/* Floating-point loads */
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