RFR: 8345766: C2 should emit macro nodes for ModF/ModD instead of calls during parsing [v2]

[Theo Weidmann]

> C2 currently emits runtime calls if the platform rules do not support lowering floating point remainder operations. For example, for float:
> 
> https://github.com/openjdk/jdk/blob/fbbc7c35f422294090b8c7a02a19ab2fb67c7070/src/hotspot/share/opto/parse2.cpp#L2305-L2318
> 
> https://github.com/openjdk/jdk/blob/fbbc7c35f422294090b8c7a02a19ab2fb67c7070/src/hotspot/share/opto/parse2.cpp#L1099-L1109
> 
> The only platform, which currently supports this, however, is x86_32. On all other platforms, runtime calls are generated directly during parsing, which prevent any constant folding or other idealizations. Even C1 can perform these optimizations, resulting in significantly lower C2 performance compared to C1 for simple test cases. This function was observed to be around 15x slower with C2 compared to C1 due to redundant runtime calls:
> 
> 
> public static double process(final double x) {
>         double w = (double) 0.1;
>         double p = 0;
>         p = (double) (3.109615012413746E307 % (w % Z));
>         p = (double) (7.614949555185036E307 / (x % x)); // <- return value only dependends on this line
>         return (double) (x * p);
> }
> 
> 
> To fix this, this PR turns ModFNode and ModDNode into macros, which are always created during parsing. They support idealization (constant folding) and are lowered to runtime calls during macro expansion. For simplicity, these operations will now also call into the runtime on x86_32, as this platform is deprecated.

Theo Weidmann has updated the pull request incrementally with one additional commit since the last revision:

  Update src/hotspot/share/opto/callnode.cpp
  
  Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/22786/files
  - new: https://git.openjdk.org/jdk/pull/22786/files/b4e9838c..974f64b3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22786&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22786&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/22786.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22786/head:pull/22786

PR: https://git.openjdk.org/jdk/pull/22786