[llvm] [clang] [RISCV] Add sifive-p670 processor (PR #79015)

[Craig Topper via cfe-commits]

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@@ -2000,6 +2000,14 @@ bool RISCVTargetLowering::shouldSinkOperands(
   if (!I->getType()->isVectorTy() || !Subtarget.hasVInstructions())
     return false;
 
+  // Don't sink splat operands if the target prefers it. Some targets requires
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topperc wrote:

These should probably be stacked the other way. Adding a new cpu that uses existing extensions with no new scheduler mode is easy to get approved. Adding a new tuning flag potentially requires more discussion. So in my opinion the stack should be

-Add new mcpu=sifive-p670
-Add TuneSinkSplatOperand and add to sifive-p670

https://github.com/llvm/llvm-project/pull/79015