Merge commit '41ac94d637b3' from apple/stable/20210107 into swift/release/5.5

Author: git apple-llvm automerger

llvm/lib/Target/ARM/ARMFrameLowering.cpp

@@ -1134,19 +1134,16 @@ void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
       // The aligned reloads from area DPRCS2 are not inserted here.
       if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs)
         continue;
-
       if (Reg == ARM::LR && !isTailCall && !isVarArg && !isInterrupt &&
-          !isCmseEntry && !isTrap && STI.hasV5TOps()) {
-        if (MBB.succ_empty()) {
-          Reg = ARM::PC;
-          // Fold the return instruction into the LDM.
-          DeleteRet = true;
-          LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
-          // We 'restore' LR into PC so it is not live out of the return block:
-          // Clear Restored bit.
-          Info.setRestored(false);
-        } else
-          LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD;
+          !isCmseEntry && !isTrap && AFI->getArgumentStackToRestore() == 0 &&
+          STI.hasV5TOps() && MBB.succ_empty()) {
+        Reg = ARM::PC;
+        // Fold the return instruction into the LDM.
+        DeleteRet = true;
+        LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
+        // We 'restore' LR into PC so it is not live out of the return block:
+        // Clear Restored bit.
+        Info.setRestored(false);
       }
 
       // If NoGap is true, pop consecutive registers and then leave the rest

llvm/test/CodeGen/ARM/tailcc-call.ll

@@ -191,3 +191,15 @@ define tailcc void @fromtail_toC() {
   call void @Ccallee_stack4([4 x i32] undef, i32 42)
   ret void
 }
+
+; Don't try to return by popping pc if there's stack to reclaim.
+define tailcc void @notail_stackclean([4 x i32], i32) {
+; COMMON-LABEL: notail_stackclean:
+; COMMON: pop {r7, lr}
+; COMMON: add sp, #8
+; COMMON: bx lr
+
+
+  call void @callee_stack0()
+  ret void
+}