Revert "[NVPTX] Prefer prmt.b32 over bfi.b32 (#110766)"

This reverts commit 3f9998a.

It breaks downstream tests with egregious numerical differences.

Unfortunately no upstream tests are broken, but the fact that
a prior iteration of the commit (pre-optimization) does work
with our downstream tests (coming from the Triton repo) supports
the claim that the final version of the commit is incorrect.

Reverting now so that the original author can evaluate.

Author: cota

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

@@ -2332,23 +2332,20 @@ SDValue NVPTXTargetLowering::LowerBUILD_VECTOR(SDValue Op,
     // Lower non-const v4i8 vector as byte-wise constructed i32, which allows us
     // to optimize calculation of constant parts.
     if (VT == MVT::v4i8) {
-      SDValue PRMT__10 = DAG.getNode(
-          NVPTXISD::PRMT, DL, MVT::v4i8,
-          {DAG.getAnyExtOrTrunc(Op->getOperand(0), DL, MVT::i32),
-           DAG.getAnyExtOrTrunc(Op->getOperand(1), DL, MVT::i32),
-           DAG.getConstant(0x3340, DL, MVT::i32),
-           DAG.getConstant(NVPTX::PTXPrmtMode::NONE, DL, MVT::i32)});
-      SDValue PRMT32__ = DAG.getNode(
-          NVPTXISD::PRMT, DL, MVT::v4i8,
-          {DAG.getAnyExtOrTrunc(Op->getOperand(2), DL, MVT::i32),
-           DAG.getAnyExtOrTrunc(Op->getOperand(3), DL, MVT::i32),
-           DAG.getConstant(0x4033, DL, MVT::i32),
-           DAG.getConstant(NVPTX::PTXPrmtMode::NONE, DL, MVT::i32)});
-      SDValue PRMT3210 = DAG.getNode(
-          NVPTXISD::PRMT, DL, MVT::v4i8,
-          {PRMT__10, PRMT32__, DAG.getConstant(0x5410, DL, MVT::i32),
-           DAG.getConstant(NVPTX::PTXPrmtMode::NONE, DL, MVT::i32)});
-      return DAG.getNode(ISD::BITCAST, DL, VT, PRMT3210);
+      SDValue C8 = DAG.getConstant(8, DL, MVT::i32);
+      SDValue E01 = DAG.getNode(
+          NVPTXISD::BFI, DL, MVT::i32,
+          DAG.getAnyExtOrTrunc(Op->getOperand(1), DL, MVT::i32),
+          DAG.getAnyExtOrTrunc(Op->getOperand(0), DL, MVT::i32), C8, C8);
+      SDValue E012 =
+          DAG.getNode(NVPTXISD::BFI, DL, MVT::i32,
+                      DAG.getAnyExtOrTrunc(Op->getOperand(2), DL, MVT::i32),
+                      E01, DAG.getConstant(16, DL, MVT::i32), C8);
+      SDValue E0123 =
+          DAG.getNode(NVPTXISD::BFI, DL, MVT::i32,
+                      DAG.getAnyExtOrTrunc(Op->getOperand(3), DL, MVT::i32),
+                      E012, DAG.getConstant(24, DL, MVT::i32), C8);
+      return DAG.getNode(ISD::BITCAST, DL, VT, E0123);
     }
     return Op;
   }