RFR: 8270086: ARM32-softfp: Do not load CONSTANT_double using the condy helper methods in the interpreter

[Aleksey Shipilev]

On Tue, 13 Jul 2021 13:17:58 GMT, Christoph Göttschkes <cgo at openjdk.org> wrote:

> Hi,
> 
> please review this fix for the template interpreter for ARM32-softfp.
> 
> With the introduction of condy, the interpreter started to load double constants using the condy_helper, which is unnecessary. Also, the [resolve_ldc](https://github.com/openjdk/jdk/blob/8973867fb9568a3a527b763c9ce10cebdfb306d0/src/hotspot/share/interpreter/interpreterRuntime.cpp#L148) implementation of the interpreter runtime might not be designed to load constant values. It should only load strings and condy.
> 
> https://github.com/openjdk/jdk/blob/2ee56fd1cf4acd634e19cc77b7c9a6858e1c315a/src/hotspot/cpu/arm/templateTable_arm.cpp#L515-L560
> 
> I refactored the ldc2_w bytecode imlpementation. Now, the ifdef between soft and hard float covers both types, CONSTANT_Long and CONSTANT_Double. I did this, because for the softfp, we can use a conditional cmp, since double and long are both placed on the stack in the same way. The same is also done for CONSTANT_Integer and CONSTANT_Float in the ldc bytecode implementation. Also, I think it is easier to follow the code this way.
> 
> Old ldc2_w implementation (before condy was implemented for ARM32):
> 
> https://github.com/openjdk/jdk/blob/7101b28dc3903be27cb46a00781f4d74f81f1114/src/hotspot/cpu/arm/templateTable_arm.cpp#L497-L537
> 
> Testing: ARMv7-A (hardfp) hotspot tier1, ARMv5TE (softfp) hotspot tier1

TBH, I am not even sure that we need to check `__ABI_HARD__` here instead of `__SOFTFP__` here. Looking at `TemplateTable::dload` and `load_category2_local`, I would have expected `__SOFTFP__`...

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PR: https://git.openjdk.java.net/jdk/pull/4767