[PATCH] D129715: [LoongArch] Optimize the loading of floating-point immediates

[WÁNG Xuěruì via Phabricator via llvm-commits]

xen0n added a comment.

In D129715#3650519 <https://reviews.llvm.org/D129715#3650519>, @SixWeining wrote:

> This change optimzies out the constant pool for loading floating-point constant by li+i2f, so I think the title could be:  "[LoongArch] Optimize the loading of floating-point immediates by li+i2f", and it' better that use a common case in the summary but not the 1.0.
>
> To other reviewers: we tested this optimization with an internal llvm version (llvm13) on 3A5000, and it shows that SPEC CPU2006 FP score increases 1% in average. 470.lbm score increases 8.9%. But we wonder why other architectures have not done so? Is there any potential issue?

Hmm yeah I overlooked the overly generic patch title (I was reviewing the code in the metro). But it seems the `i2f` isn't found anywhere in the repo nor the commit history, instead there's `i2fp` but that usage isn't common either. I assume the `i2fp` is short for the `{s,u}itofp` IR insn. Then the description is incorrect because the `{s,u}itofp` transfers the numeric value, not bit layout.

I think the title could be further simplified into something like "[LoongArch] Load FP immediates by movgr2fr from materialized integer", and the justification (such as the performance numbers you cited) could be put in the commit message body. What do you think?


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https://reviews.llvm.org/D129715