[llvm] [RISCV] Add Tune to DontSinkSplatOperands (PR #79199)

[Wang Pengcheng via llvm-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
+  // S2V transfer buffers and we can run out of them copying the same value
+  // repeatedly.
+  // FIXME: It could still be worth doing if it would improve vector register
+  // pressure and prevent a vector spill.
+  if (Subtarget.dontSinkSplatOperands())
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wangpc-pp wrote:

Is this the only place to control the generation of sinked V instructions?

https://github.com/llvm/llvm-project/pull/79199