[llvm-branch-commits] [lld] [lld][LoongArch] Convert TLS IE to LE in the normal or medium code model (PR #123680)

[Lu Weining via llvm-branch-commits]

================
@@ -1002,6 +1008,87 @@ static bool relax(Ctx &ctx, InputSection &sec) {
   return changed;
 }
 
+// Convert TLS IE to LE in the normal or medium code model.
+// Original code sequence:
+//  * pcalau12i $a0, %ie_pc_hi20(sym)
+//  * ld.d      $a0, $a0, %ie_pc_lo12(sym)
+//
+// The code sequence converted is as follows:
+//  * lu12i.w   $a0, %le_hi20(sym)  # le_hi20 != 0, otherwise NOP
+//  * ori $a0   $a0, %le_lo12(sym)
+//
+// When relaxation enables, redundant NOPs can be removed.
+void LoongArch::tlsIeToLe(uint8_t *loc, const Relocation &rel,
+                          uint64_t val) const {
+  assert(isInt<32>(val) &&
+         "val exceeds the range of medium code model in tlsIeToLe");
+
+  bool isUInt12 = isUInt<12>(val);
+  const uint32_t currInsn = read32le(loc);
+  switch (rel.type) {
+  case R_LARCH_TLS_IE_PC_HI20:
+    if (isUInt12)
+      write32le(loc, insn(ANDI, R_ZERO, R_ZERO, 0)); // nop
+    else
+      write32le(loc, insn(LU12I_W, getD5(currInsn), extractBits(val, 31, 12),
+                          0)); // lu12i.w $a0, %le_hi20
+    break;
+  case R_LARCH_TLS_IE_PC_LO12:
+    if (isUInt12)
+      write32le(loc, insn(ORI, getD5(currInsn), R_ZERO,
+                          val)); // ori $a0, $r0, %le_lo12
+    else
+      write32le(loc, insn(ORI, getD5(currInsn), getJ5(currInsn),
+                          lo12(val))); // ori $a0, $a0, %le_lo12
+    break;
+  }
+}
+
+void LoongArch::relocateAlloc(InputSectionBase &sec, uint8_t *buf) const {
+  const unsigned bits = ctx.arg.is64 ? 64 : 32;
+  uint64_t secAddr = sec.getOutputSection()->addr;
+  if (auto *s = dyn_cast<InputSection>(&sec))
+    secAddr += s->outSecOff;
+  else if (auto *ehIn = dyn_cast<EhInputSection>(&sec))
+    secAddr += ehIn->getParent()->outSecOff;
+  bool isExtreme = false;
+  const MutableArrayRef<Relocation> relocs = sec.relocs();
+  for (size_t i = 0, size = relocs.size(); i != size; ++i) {
+    Relocation &rel = relocs[i];
+    uint8_t *loc = buf + rel.offset;
+    uint64_t val = SignExtend64(
+        sec.getRelocTargetVA(ctx, rel, secAddr + rel.offset), bits);
+
+    switch (rel.expr) {
+    case R_RELAX_HINT:
+      continue;
+    case R_RELAX_TLS_IE_TO_LE:
+      if (rel.type == R_LARCH_TLS_IE_PC_HI20) {
+        // LoongArch does not support IE to LE optimize in the extreme code
+        // model. In this case, the relocs are as follows:
+        //
+        //  * i   -- R_LARCH_TLS_IE_PC_HI20
+        //  * i+1 -- R_LARCH_TLS_IE_PC_LO12
+        //  * i+2 -- R_LARCH_TLS_IE64_PC_LO20
+        //  * i+3 -- R_LARCH_TLS_IE64_PC_HI12
+        isExtreme =
+            (i + 2 < size && relocs[i + 2].type == R_LARCH_TLS_IE64_PC_LO20);
+      }
+      if (isExtreme) {
+        rel.expr = getRelExpr(rel.type, *rel.sym, loc);
+        val = SignExtend64(sec.getRelocTargetVA(ctx, rel, secAddr + rel.offset),
+                           bits);
+        relocateNoSym(loc, rel.type, val);
+      } else
+        tlsIeToLe(loc, rel, val);
----------------
SixWeining wrote:

Use braces for the `else if` and `else` block to keep it uniform with the `if` block. See: https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

```suggestion
      } else {
        tlsIeToLe(loc, rel, val);
      }
```

https://github.com/llvm/llvm-project/pull/123680