Address comments

Author: vladimirradosavljevic

llvm/lib/CodeGen/MachineCopyPropagation.cpp

@@ -707,10 +707,11 @@ bool MachineCopyPropagation::hasOverlappingMultipleDef(
   return false;
 }
 
-/// Return true if it is safe to update the users of the source register of the
-/// copy.
+/// Return true if it is safe to update all users of the \p CopySrc register
+/// in the given \p Copy instruction.
 bool MachineCopyPropagation::canUpdateSrcUsers(const MachineInstr &Copy,
                                                const MachineOperand &CopySrc) {
+  assert(CopySrc.isReg() && "Expected a register operand");
   for (auto *SrcUser : Tracker.getSrcUsers(CopySrc.getReg(), *TRI)) {
     if (hasImplicitOverlap(*SrcUser, CopySrc))
       return false;

llvm/test/CodeGen/AArch64/machine-cp-backward-uses.mir

@@ -0,0 +1,58 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -mtriple=aarch64-none-linux-gnu -run-pass machine-cp -verify-machineinstrs -o - %s | FileCheck %s
+
+# Normal case
+---
+name: test1
+body: |
+  bb.0:
+    liveins: $w2
+    ; CHECK-LABEL: name: test1
+    ; CHECK: liveins: $w2
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: renamable $w0 = MOVi32imm 5
+    ; CHECK-NEXT: renamable $w3 = ADDWrr renamable $w0, killed renamable $w2
+    ; CHECK-NEXT: RET_ReallyLR implicit killed $w0
+    renamable $w1 = MOVi32imm 5
+    renamable $w3 = ADDWrr renamable $w1, killed renamable $w2
+    renamable $w0 = COPY killed renamable $w1
+    RET_ReallyLR implicit killed $w0
+...
+
+# Not renamable use
+---
+name: test2
+body: |
+  bb.0:
+    liveins: $w2
+    ; CHECK-LABEL: name: test2
+    ; CHECK: liveins: $w2
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: renamable $w1 = MOVi32imm 5
+    ; CHECK-NEXT: renamable $w3 = ADDWrr $w1, killed renamable $w2
+    ; CHECK-NEXT: renamable $w0 = COPY killed renamable $w1
+    ; CHECK-NEXT: RET_ReallyLR implicit killed $w0
+    renamable $w1 = MOVi32imm 5
+    renamable $w3 = ADDWrr $w1, killed renamable $w2
+    renamable $w0 = COPY killed renamable $w1
+    RET_ReallyLR implicit killed $w0
+...
+
+# Implicit use
+---
+name: test3
+body: |
+  bb.0:
+    liveins: $w2
+    ; CHECK-LABEL: name: test3
+    ; CHECK: liveins: $w2
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: renamable $w1 = MOVi32imm 5
+    ; CHECK-NEXT: renamable $w3 = ADDWrr renamable $w1, killed renamable $w2, implicit $w1
+    ; CHECK-NEXT: renamable $w0 = COPY killed renamable $w1
+    ; CHECK-NEXT: RET_ReallyLR implicit killed $w0
+    renamable $w1 = MOVi32imm 5
+    renamable $w3 = ADDWrr renamable $w1, killed renamable $w2, implicit $w1
+    renamable $w0 = COPY killed renamable $w1
+    RET_ReallyLR implicit killed $w0
+...