[llvm] [RISCV] Merge ADDI with X0 into base offset (PR #78940)

[Craig Topper via llvm-commits]

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@@ -193,9 +193,17 @@ bool RISCVMergeBaseOffsetOpt::foldLargeOffset(MachineInstr &Hi,
     if (AddiImmOp.getTargetFlags() != RISCVII::MO_None)
       return false;
     Register AddiReg = OffsetTail.getOperand(1).getReg();
-    if (!AddiReg.isVirtual())
-      return false;
     int64_t OffLo = AddiImmOp.getImm();
+
+    // Handle rs1 of ADDI is X0.
+    if (AddiReg == RISCV::X0) {
+      LLVM_DEBUG(dbgs() << "  Offset Instrs: " << OffsetTail);
+      int64_t Offset = OffLo;
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topperc wrote:

Why do we need a new variable `Offset`?

https://github.com/llvm/llvm-project/pull/78940