update tests

Author: rez5427

clang/test/CodeGen/msp430-abi-complex.c

@@ -202,7 +202,7 @@ float _Complex complex_float_res(void) {
 // CHECK-DAG: clr r12
 // CHECK-DAG: mov #16256, r13
   __imag__ res = -1;
-// CHECK-DAG: clr r14
+// CHECK-DAG: mov r12, r14
 // CHECK-DAG: mov #-16512, r15
   return res;
 // CHECK:     ret

llvm/lib/CodeGen/RegisterCoalescer.cpp

@@ -1328,6 +1328,8 @@ bool RegisterCoalescer::reMaterializeDef(const CoalescerPair &CP,
 
   // Skip rematerialization for physical registers used as return values within
   // the same basic block to enable better coalescing.
+  
+    
   if (DstReg.isPhysical()) {
     MachineBasicBlock *MBB = CopyMI->getParent();
     if (DefMI->getParent() == MBB) {
@@ -1351,6 +1353,34 @@ bool RegisterCoalescer::reMaterializeDef(const CoalescerPair &CP,
             break;
           // If there's a return instruction that uses this register, skip remat
           if (MI.isReturn() && MI.readsRegister(DstReg, TRI)) {
+            // Exception: if DefMI is moving a constant and SrcReg has no other uses
+            // (besides copies), rematerialization is beneficial to eliminate the def
+            if (DefMI->isMoveImmediate()) {
+              // Quick check: if there's only one use and it's this copy, definitely remat
+              if (MRI->hasOneNonDBGUse(SrcReg)) {
+                LLVM_DEBUG(dbgs() << "\tAllow remat: single use constant move\n");
+                break;
+              }
+              
+              // Check all uses to see if they're all copies
+              bool OnlyUsedByCopies = true;
+              unsigned UseCount = 0;
+              for (const MachineOperand &MO : MRI->use_operands(SrcReg)) {
+                const MachineInstr *UseMI = MO.getParent();  // 改为 const
+                if (!UseMI->isCopy() && !UseMI->isSubregToReg()) {
+                  OnlyUsedByCopies = false;
+                  break;
+                }
+                UseCount++;
+              }
+              
+              if (OnlyUsedByCopies && UseCount > 0) {
+                LLVM_DEBUG(dbgs() << "\tAllow remat: constant move only used by "
+                                  << UseCount << " copies\n");
+                break; // Allow rematerialization
+              }
+            }
+            
             LLVM_DEBUG(dbgs() << "\tSkip remat for return register: "
                               << printReg(DstReg, TRI) << '\n');
             return false;