Revert "[AArch64] Lower extending sitofp using tbl (#92528)"

This reverts commit d1a4f0c.

There are reports about test failures with Eigen and JAX.

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -8331,8 +8331,7 @@ bool CodeGenPrepare::optimizeInst(Instruction *I, ModifyDT &ModifiedDT) {
     if (OptimizeNoopCopyExpression(CI, *TLI, *DL))
       return true;
 
-    if ((isa<UIToFPInst>(I) || isa<SIToFPInst>(I) || isa<FPToUIInst>(I) ||
-         isa<TruncInst>(I)) &&
+    if ((isa<UIToFPInst>(I) || isa<FPToUIInst>(I) || isa<TruncInst>(I)) &&
         TLI->optimizeExtendOrTruncateConversion(
             I, LI->getLoopFor(I->getParent()), *TTI))
       return true;

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -15965,24 +15965,6 @@ static Value *createTblShuffleForZExt(IRBuilderBase &Builder, Value *Op,
   return Result;
 }
 
-static Value *createTblShuffleForSExt(IRBuilderBase &Builder, Value *Op,
-                                      FixedVectorType *DstTy,
-                                      bool IsLittleEndian) {
-  auto *SrcTy = cast<FixedVectorType>(Op->getType());
-  auto SrcWidth = cast<IntegerType>(SrcTy->getElementType())->getBitWidth();
-  auto DstWidth = cast<IntegerType>(DstTy->getElementType())->getBitWidth();
-
-  SmallVector<int> Mask;
-  if (!createTblShuffleMask(SrcWidth, DstWidth, SrcTy->getNumElements(),
-                            !IsLittleEndian, Mask))
-    return nullptr;
-
-  auto *FirstEltZero = Builder.CreateInsertElement(
-      PoisonValue::get(SrcTy), Builder.getInt8(0), uint64_t(0));
-
-  return Builder.CreateShuffleVector(Op, FirstEltZero, Mask);
-}
-
 static void createTblForTrunc(TruncInst *TI, bool IsLittleEndian) {
   IRBuilder<> Builder(TI);
   SmallVector<Value *> Parts;
@@ -16163,29 +16145,14 @@ bool AArch64TargetLowering::optimizeExtendOrTruncateConversion(
     Value *ZExt = createTblShuffleForZExt(
         Builder, I->getOperand(0), FixedVectorType::getInteger(DstTy),
         FixedVectorType::getInteger(DstTy), Subtarget->isLittleEndian());
-    assert(ZExt && "Cannot fail for the i8 to float conversion");
+    if (!ZExt)
+      return false;
     auto *UI = Builder.CreateUIToFP(ZExt, DstTy);
     I->replaceAllUsesWith(UI);
     I->eraseFromParent();
     return true;
   }
 
-  auto *SIToFP = dyn_cast<SIToFPInst>(I);
-  if (SIToFP && SrcTy->getElementType()->isIntegerTy(8) &&
-      DstTy->getElementType()->isFloatTy()) {
-    IRBuilder<> Builder(I);
-    auto *Shuffle = createTblShuffleForSExt(Builder, I->getOperand(0),
-                                            FixedVectorType::getInteger(DstTy),
-                                            Subtarget->isLittleEndian());
-    assert(Shuffle && "Cannot fail for the i8 to float conversion");
-    auto *Cast = Builder.CreateBitCast(Shuffle, VectorType::getInteger(DstTy));
-    auto *AShr = Builder.CreateAShr(Cast, 24, "", true);
-    auto *SI = Builder.CreateSIToFP(AShr, DstTy);
-    I->replaceAllUsesWith(SI);
-    I->eraseFromParent();
-    return true;
-  }
-
   // Convert 'fptoui <(8|16) x float> to <(8|16) x i8>' to a wide fptoui
   // followed by a truncate lowered to using tbl.4.
   auto *FPToUI = dyn_cast<FPToUIInst>(I);