[llvm] [RISCV][llvm] Preliminary P extension codegen support (PR #162668)

[Christian Herber via llvm-commits]

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@@ -479,6 +490,24 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
       ISD::FTRUNC,       ISD::FRINT,         ISD::FROUND,
       ISD::FROUNDEVEN,   ISD::FCANONICALIZE};
 
+  if (Subtarget.hasStdExtP()) {
+    // load/store are already handled by pattern matching
+    SmallVector<MVT, 2> VTs = {MVT::v2i16, MVT::v4i8};
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christian-herber-nxp wrote:

somewhat related but likely unrelated here, there is also similar use of the pack instructions with x0, to extract a byte/halfword/word from specific positions: https://lists.riscv.org/g/tech-p-ext/message/753

https://github.com/llvm/llvm-project/pull/162668