[llvm] [RISCV] Don't fold offsets into auipc if offset is larger than the reference global variable. (PR #135297)

[Craig Topper via llvm-commits]

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@@ -142,9 +142,21 @@ bool RISCVMergeBaseOffsetOpt::detectFoldable(MachineInstr &Hi,
 // Update the offset in Hi and Lo instructions.
 // Delete the tail instruction and update all the uses to use the
 // output from Lo.
-void RISCVMergeBaseOffsetOpt::foldOffset(MachineInstr &Hi, MachineInstr &Lo,
+bool RISCVMergeBaseOffsetOpt::foldOffset(MachineInstr &Hi, MachineInstr &Lo,
                                          MachineInstr &Tail, int64_t Offset) {
   assert(isInt<32>(Offset) && "Unexpected offset");
+
+  // If Hi is an AUIPC, don't fold the offset if it is outside the bounds of
+  // the global object. The object may be within 2GB of the PC, but addresses
+  // outside of the object might not be.
+  if (Hi.getOpcode() == RISCV::AUIPC && Hi.getOperand(1).isGlobal()) {
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topperc wrote:

We will also try fold ConstantPool and BlockAddress offsets in this pass. Though I think the main reason for them to be in this pass is because this pass also folds the ADDI into load/store instructions.

https://github.com/llvm/llvm-project/pull/135297