[llvm] [RISCV][GISEL] instruction-select for G_SPLAT_VECTOR (PR #111193)

[Craig Topper via llvm-commits]

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@@ -800,6 +812,33 @@ void RISCVInstructionSelector::preISelLower(MachineInstr &MI,
     replacePtrWithInt(MI.getOperand(1), MIB);
     MI.setDesc(TII.get(TargetOpcode::G_AND));
     MRI->setType(DstReg, sXLen);
+    break;
+  }
+  case TargetOpcode::G_SPLAT_VECTOR: {
+    // Convert integer SPLAT_VECTOR to VMV_V_X_VL and floating-point
+    // SPLAT_VECTOR to VFMV_V_F_VL to reduce isel burden.
+    Register Scalar = MI.getOperand(1).getReg();
+    bool IsGPRSplat = isRegInGprb(Scalar);
+    const LLT sXLen = LLT::scalar(STI.getXLen());
+    if (IsGPRSplat && TypeSize::isKnownLT(MRI->getType(Scalar).getSizeInBits(),
+                                          sXLen.getSizeInBits()))
+      Scalar = MIB.buildAnyExt(sXLen, Scalar).getReg(0);
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topperc wrote:

Why doesn't this G_ANYEXT need special selection like the passthru and vlmax?

https://github.com/llvm/llvm-project/pull/111193