[PATCH] D80907: [PowerPC] refactor convertToImmediateForm - NFC

[ChenZheng via Phabricator via llvm-commits]

shchenz marked an inline comment as done.
shchenz added inline comments.


================
Comment at: llvm/lib/Target/PowerPC/PPCInstrInfo.cpp:3421
+    // Set the bits (        MB + 32        ) to (        ME + 32        ).
+    uint64_t Mask = ((1LLU << (32 - MB)) - 1) & ~((1LLU << (31 - ME)) - 1);
+    InVal &= Mask;
----------------
steven.zhang wrote:
> shchenz wrote:
> > shchenz wrote:
> > > steven.zhang wrote:
> > > > It can be improved with APInt utility.
> > > ```
> > >  APInt Mask = APInt::getBitsSetWithWrap(32, 32 - ME - 1, 32 - MB);
> > >  // Current APInt::getBitsSetWithWrap sets all bits to 0 if loBit is equal to highBit.
> > >  // If MB - ME == 1, we expect a full set mask instead of 0.
> > >  if (MBSrc - MESrc == 1)
> > >     Mask.setAllBits();
> > > ```
> > > 
> > > Personally, I think using a raw APInt would be better than above statements?
> > Should be a raw int... not raw APInt
> If MB - ME == 1, the current implementation is still zero.
> ```
> #include <stdio.h>
> 
> int main() {
>          long long ME=23;
>          long long MB = ME + 1;
>          unsigned long long Mask = ((1LLU << (32 - MB)) - 1) & ~((1LLU << (31 - ME)) - 1);
>          printf("%llx\n", Mask);
>          return 0;
> }
> ```
> clang test.c;./a.out
> 0
OK, thanks for pointing it out. Then the mask calculated here should be a bug. If MB - ME == 1, we expect full mask instead of zero mask.

I suggest we don't fix this in this NFC patch. This patch intends to make the `convertToImmediateForm` light and mostly move codes from  `convertToImmediateForm` to new created function `SimplifyToLI`.


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  https://reviews.llvm.org/D80907/new/

https://reviews.llvm.org/D80907