[llvm] [RISCV] Hoist immediate addresses from loads/stores (PR #83644)

[Wang Pengcheng via llvm-commits]

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@@ -162,6 +162,14 @@ InstructionCost RISCVTTIImpl::getIntImmCostInst(unsigned Opcode, unsigned Idx,
     // split up large offsets in GEP into better parts than ConstantHoisting
     // can.
     return TTI::TCC_Free;
+  case Instruction::Store:
+    // If the address is a constant, use the materialization cost.
+    if (Idx == 1)
+      return getIntImmCost(Imm, Ty, CostKind);
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wangpc-pp wrote:

For addresses in [0, 2048), we can use `ld/sd a0, offset(zero)`.
(though I don't know if this is a common case)

https://github.com/llvm/llvm-project/pull/83644