[code-reflection] RFR: PTX backend implementation for HAT

[Gary Frost]

On Fri, 19 Jul 2024 19:36:16 GMT, Ruby Chen <duke at openjdk.org> wrote:

> Implemented a PTX backend for HAT kernel execution; PTX will run on machines with supporting Nvidia GPUs. Currently works for Squares and Mandel kernel examples.
> 
> Also starting to implement a BlackScholes kernel for HAT.

At this time I focused on the PTXCodeBuilder. 

Generally look at options other than calling append() directly, build more fine grained builder helpers.

hat/backends/ptx/src/main/java/hat/backend/PTXCodeBuilder.java line 90:

> 88: 
> 89:     public void ptxHeader(int major, int minor, String target, int addressSize) {
> 90:         append(".version ").append(String.valueOf(major)).dot().append(String.valueOf(minor)).nl();

I see quite a few uses of append in this file.  

Generally when using your own builder 'dialect' (in this case PTXBuilder), consider each use of raw append and determine whether you should add a specific build method. 

Also don't include '.' and ' ' (space) in strings  (as in append(".version ") prefer explicit dot() and space()

So maybe you add a specific version(), major(int) and minor(int) so your code would be 

dot().version().space().major(major).dot().minor(minor).nl()

hat/backends/ptx/src/main/java/hat/backend/PTXCodeBuilder.java line 98:

> 96:     public void functionHeader(String funcName, boolean entry, TypeElement yieldType) {
> 97:         if (entry) {
> 98:             append(".visible .entry ");

dot().visible().space().entry().space()?

hat/backends/ptx/src/main/java/hat/backend/PTXCodeBuilder.java line 105:

> 103:             returnReg = new PTXRegister(getOrdinal(resultType(yieldType)), resultType(yieldType));
> 104:             returnReg.name("%retReg");
> 105:             oparen().param().space().printParamType(yieldType);

avoid prefixing with 'print' like this, everything going through the builder is essentially printing. Maybe just 'paramType(yieldType)'

hat/backends/ptx/src/main/java/hat/backend/PTXCodeBuilder.java line 263:

> 261:         append("cvta.to").global().addrSize().space().printField(Field.KC_ADDR).commaSpace()
> 262:                 .printAndAddVar(paramMap.get("kc"), addrType()).ptxNl();
> 263:         mov().u32().space().printField(Field.NTID_X).commaSpace().append("%ntid.x").ptxNl();

again 'printField ()' -> 'field()' , printAndAddVar() -> addVarAndType() .
consider 'cvta().dot().to()'
Rather than repeating these suggestions, look at all uses of printXXX and append and see it we can de

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PR Review: https://git.openjdk.org/babylon/pull/188#pullrequestreview-2193337450
PR Review Comment: https://git.openjdk.org/babylon/pull/188#discussion_r1687658595
PR Review Comment: https://git.openjdk.org/babylon/pull/188#discussion_r1687661963
PR Review Comment: https://git.openjdk.org/babylon/pull/188#discussion_r1687661167
PR Review Comment: https://git.openjdk.org/babylon/pull/188#discussion_r1687669659