[llvm] [RISCV][GlobalISel] Select G_GLOBAL_VALUE (PR #70091)

[Craig Topper via llvm-commits]

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@@ -483,6 +489,126 @@ bool RISCVInstructionSelector::selectConstant(MachineInstr &MI,
   return true;
 }
 
+bool RISCVInstructionSelector::selectGlobalValue(
+    MachineInstr &MI, MachineIRBuilder &MIB, MachineRegisterInfo &MRI) const {
+  assert(MI.getOpcode() == TargetOpcode::G_GLOBAL_VALUE &&
+         "Expected G_GLOBAL_VALUE");
+
+  auto *GV = MI.getOperand(1).getGlobal();
+  if (GV->isThreadLocal()) {
+    // TODO: implement this case.
+    return false;
+  }
+
+  switch (TM.getCodeModel()) {
+  default: {
+    reportGISelFailure(const_cast<MachineFunction &>(*MF), *TPC, *MORE,
+                       getName(), "Unsupported code model for lowering", MI);
+    return false;
+  }
+  case CodeModel::Small: {
+    Register DefReg = MI.getOperand(0).getReg();
+    const LLT DefTy = MRI.getType(DefReg);
+    MachineInstr *Result = nullptr;
+
+    // When HWASAN is used and tagging of global variables is enabled
+    // they should be accessed via the GOT, since the tagged address of a global
+    // is incompatible with existing code models. This also applies to non-pic
+    // mode.
+    if (TM.isPositionIndependent() && GV->isDSOLocal() &&
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topperc wrote:

I meant the whole position independent code block.  It's independent of code model.

https://github.com/llvm/llvm-project/pull/70091