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LLVM backend for 6502
aa2200c5fa
The vec_sld interface provides access to the vsldoi instruction. Unlike most of the vec_* interfaces, we do not attempt to change the generated code for vec_sld based on the endian mode. It is too difficult to correctly infer the desired semantics because of different element types, and the corrected instruction sequence is expensive, involving loading a permute control vector and performing a generalized permute. For GCC, this was implemented as "Don't touch the vec_sld" implementation. When it came time for the LLVM implementation, I did the same thing. However, this was hasty and incorrect. In LLVM's version of altivec.h, vec_sld was previously defined in terms of the vec_perm interface. Because vec_perm semantics are adjusted for little endian, this means that leaving vec_sld untouched causes it to generate something different for LE than for BE. Not good. This back-end patch accompanies the changes to altivec.h that change vec_sld's behavior for little endian. Those changes mean that we see slightly different code in the back end when trying to recognize a VSLDOI instruction in isVSLDOIShuffleMask. In particular, a ShuffleKind of 1 (where the two inputs are identical) must now be treated the same way as a ShuffleKind of 2 (little endian with different inputs) when little endian mode is in force. This is because ShuffleKind of 1 is defined using big-endian numbering. This has a ripple effect on LowerBUILD_VECTOR, where we create our own internal VSLDOI instructions. Because these are a ShuffleKind of 1, they will now have their shift amounts subtracted from 16 when recognizing the shuffle mask. To avoid problems we have to subtract them from 16 again before creating the VSLDOI instructions. There are a couple of other uses of BuildVSLDOI, but these do not need to be modified because the shift amount is 8, which is unchanged when subtracted from 16. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242296 91177308-0d34-0410-b5e6-96231b3b80d8 |
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| tools | ||
| unittests | ||
| utils | ||
| .arcconfig | ||
| .clang-format | ||
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| .gitignore | ||
| CMakeLists.txt | ||
| CODE_OWNERS.TXT | ||
| configure | ||
| CREDITS.TXT | ||
| LICENSE.TXT | ||
| llvm.spec.in | ||
| LLVMBuild.txt | ||
| Makefile | ||
| Makefile.common | ||
| Makefile.config.in | ||
| Makefile.rules | ||
| README.txt | ||
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