MIPS: .cpsetup broken for n32

[chmeeedalf]

MIPS n32 ABI requires '.cpsetup , <off | reg>, ' to generate the following sequence:

sd $gp, off ($sp)
lui $gp, label    // top half
addiu $gp, label  // bottom half
addu $gp, $gp, r

The MIPS code generator currently does not include the final addu, leading to crashes in n32 ABI position independent code.

[chmeeedalf]

Looking at it more, n32 is supposed to use whatever label, not fixed at __gnu_local_gp

[atanasyan]

Could you check that this patch fixes the issue? The patch adds the addu instruction only. __gnu_local_gp is a separate problem.
pr52785.patch.txt

[rasul247]

On Fri, Dec 18

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[chmeeedalf]

Unfortunately that's incomplete. It's adding the "absolute" address of __gnu_local_gp, which won't work to get a relative address. It really should be doing what is done for N64 below in the function, from what I can tell.

[wzssyqa]

It's due to a typo in MipsTargetELFStreamer::emitDirectiveCpsetup
This patch should work:

-  if (getABI().IsN32()) {
+#if 0
+  // We haven't support -mabicalls -mno-shared yet.
+  if (-mno-shared) {
     MCSymbol *GPSym = MCA.getContext().getOrCreateSymbol("__gnu_local_gp");
     const MipsMCExpr *HiExpr = MipsMCExpr::create(
         MipsMCExpr::MEK_HI, MCSymbolRefExpr::create(GPSym, MCA.getContext()),
@@ -1273,6 +1275,7 @@ void MipsTargetELFStreamer::emitDirectiveCpsetup(unsigned RegNo,
 
     return;
   }
+#endif