[llvm] [PowerPC] extend smaller splats into bigger splats (with fix) (PR #142194)

[Amy Kwan via llvm-commits]

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@@ -9785,13 +9802,37 @@ SDValue PPCTargetLowering::LowerBUILD_VECTOR(SDValue Op,
                                   dl);
 
   // If the sign extended value is in the range [-16,15], use VSPLTI[bhw].
-  int32_t SextVal = SignExtend32(SplatBits, SplatBitSize);
-  if (SextVal >= -16 && SextVal <= 15)
-    return getCanonicalConstSplat(SextVal, SplatSize, Op.getValueType(), DAG,
-                                  dl);
+  // Use VSPLTIW/VUPKLSW for v2i64 in range [-16,15].
+  if (SextVal >= -16 && SextVal <= 15) {
+    unsigned UseSize = SplatSize == 8 ? 4 : SplatSize;
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amy-kwan wrote:

Would it be reasonable to put that comment about the SplatSize in a comment here?

https://github.com/llvm/llvm-project/pull/142194