+static bool hasIdenticalMMOs(const MachineInstr *MI1, const MachineInstr *MI2) {
+ auto I1 = MI1->memoperands_begin(), E1 = MI1->memoperands_end();
+ auto I2 = MI2->memoperands_begin(), E2 = MI2->memoperands_end();
+ if ((E1 - I1) != (E2 - I2))
+ return false;
+ for (; I1 != E1; ++I1, ++I2) {
+ if (**I1 != **I2)
+ return false;
+ }
+ return true;
+}
+
+static void
+removeMMOsFromMemoryOperations(MachineBasicBlock::iterator MBBIStartPos,
+ MachineBasicBlock &MBBCommon) {
+ // Remove MMOs from memory operations in the common block
+ // when they do not match the ones from the block being tail-merged.
+ // This ensures later passes conservatively compute dependencies.
+ MachineBasicBlock *MBB = MBBIStartPos->getParent();
+ // Note CommonTailLen does not necessarily matches the size of
+ // the common BB nor all its instructions because of debug
+ // instructions differences.
+ unsigned CommonTailLen = 0;
+ for (auto E = MBB->end(); MBBIStartPos != E; ++MBBIStartPos)
+ ++CommonTailLen;
+
+ MachineBasicBlock::reverse_iterator MBBI = MBB->rbegin();
+ MachineBasicBlock::reverse_iterator MBBIE = MBB->rend();
+ MachineBasicBlock::reverse_iterator MBBICommon = MBBCommon.rbegin();
+ MachineBasicBlock::reverse_iterator MBBIECommon = MBBCommon.rend();
+
+ while (CommonTailLen--) {
+ assert(MBBI != MBBIE && "Reached BB end within common tail length!");
+ (void)MBBIE;
+
+ if (MBBI->isDebugValue()) {
+ ++MBBI;
+ continue;
+ }
+
+ while ((MBBICommon != MBBIECommon) && MBBICommon->isDebugValue())
+ ++MBBICommon;
+
+ assert(MBBICommon != MBBIECommon &&
+ "Reached BB end within common tail length!");
+ assert(MBBICommon->isIdenticalTo(&*MBBI) && "Expected matching MIIs!");
+
+ if (MBBICommon->mayLoad() || MBBICommon->mayStore())
+ if (!hasIdenticalMMOs(&*MBBI, &*MBBICommon))
+ MBBICommon->clearMemRefs();
+
+ ++MBBI;
+ ++MBBICommon;
+ }
+}
+