[clang] [llvm] [Mips] Add r5900 (PlayStation 2 Emotion Engine) CPU support (PR #176666)

[Rick Gaiser via cfe-commits]

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@@ -587,10 +648,20 @@ bool MipsDelaySlotFiller::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
     if (!hasUnoccupiedSlot(&*I))
       continue;
 
-    // Delay slot filling is disabled at -O0, or in microMIPS32R6.
-    if (!DisableDelaySlotFiller &&
-        (TM->getOptLevel() != CodeGenOptLevel::None) &&
-        !(InMicroMipsMode && STI.hasMips32r6())) {
+    // R5900 short loop erratum fix: skip delay slot filling for short backward
+    // loops to avoid triggering a hardware bug where short loops may exit
+    // early. The fix can be controlled with -mfix-r5900 / -mno-fix-r5900.
+    if (STI.fixR5900() && isR5900ShortLoopBranch(&*I, MBB)) {
+      LLVM_DEBUG(dbgs() << DEBUG_TYPE ": skipping delay slot fill for R5900 "
+                                      "short loop branch.\n");
+      ++R5900ShortLoopNops;
+      // Fall through to insert NOP in delay slot
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rickgaiser wrote:

I made the changes, if ok this can be resolved.

https://github.com/llvm/llvm-project/pull/176666