diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Target/Mips/MSA.txt | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/llvm/lib/Target/Mips/MSA.txt b/llvm/lib/Target/Mips/MSA.txt new file mode 100644 index 00000000000..398c7afd188 --- /dev/null +++ b/llvm/lib/Target/Mips/MSA.txt @@ -0,0 +1,30 @@ +Code Generation Notes for MSA +============================= + +Intrinsics are lowered to SelectionDAG nodes where possible in order to enable +optimisation, reduce the size of the ISel matcher, and reduce repetition in +the implementation. In a small number of cases, this can cause different +(semantically equivalent) instructions to be used in place of the requested +instruction, even when no optimisation has taken place. + +Instructions +============ + +This section describes any quirks of instruction selection for MSA. For +example, two instructions might be equally valid for some given IR and one is +chosen in preference to the other. + +vshf.w: + It is not possible to emit vshf.w when the shuffle description is + constant since shf.w covers exactly the same cases. shf.w is used + instead. It is also impossible for the shuffle description to be + unknown at compile-time due to the definition of shufflevector in + LLVM IR. + +ilvl.d, pckev.d: + It is not possible to emit ilvl.d, or pckev.d since ilvev.d covers the + same shuffle. ilvev.d will be emitted instead. + +ilvr.d, ilvod.d, pckod.d: + It is not possible to emit ilvr.d, or pckod.d since ilvod.d covers the + same shuffle. ilvod.d will be emitted instead. |
