[PATCH] D80907: [PowerPC] refactor convertToImmediateForm - NFC
Qing Shan Zhang via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 2 04:25:01 PDT 2020
steven.zhang 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;
----------------
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
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https://reviews.llvm.org/D80907/new/
https://reviews.llvm.org/D80907
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