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

[Wang Pengcheng via llvm-commits]

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@@ -1082,6 +1082,13 @@ def TuneShortForwardBranchOpt
 def HasShortForwardBranchOpt : Predicate<"Subtarget->hasShortForwardBranchOpt()">;
 def NoShortForwardBranchOpt : Predicate<"!Subtarget->hasShortForwardBranchOpt()">;
 
+// Some subtargets require a S2V transfer buffer to move scalars into vectors.
+// FIXME: Forming .vx/.vf can reduce register pressure.
+def TuneDontSinkSplatOperands
+    : SubtargetFeature<"dont-sink-splat-operands", "DontSinkSplatOperands",
+                       "true", "Don't sink splat operands to enable .vx or .vf "
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wangpc-pp wrote:

.wx and .wf?

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