diff --git a/llvm/lib/CodeGen/EarlyIfConversion.cpp b/llvm/lib/CodeGen/EarlyIfConversion.cpp
--- a/llvm/lib/CodeGen/EarlyIfConversion.cpp
+++ b/llvm/lib/CodeGen/EarlyIfConversion.cpp
@@ -557,6 +557,57 @@
   return true;
 }
 
+static unsigned operandIndex(const MachineInstr &Def, Register VReg) {
+  unsigned Idx = 0;
+  for (const MachineOperand &MO : Def.defs()) {
+    if (MO.getReg() == VReg)
+      return Idx;
+    Idx++;
+  }
+  llvm_unreachable("matching operand not found");
+}
+
+/// \return true iff the two registers are known to have the same value.
+static bool hasSameValue(const MachineRegisterInfo &MRI,
+                         const TargetInstrInfo *TII, Register TReg,
+                         Register FReg) {
+  if (TReg == FReg)
+    return true;
+
+  if (!TReg.isVirtual() || !FReg.isVirtual())
+    return false;
+
+  const MachineInstr *TDef = MRI.getUniqueVRegDef(TReg);
+  const MachineInstr *FDef = MRI.getUniqueVRegDef(FReg);
+  if (!TDef || !FDef)
+    return false;
+
+  // If there are side-effects, all bets are off.
+  if (TDef->hasUnmodeledSideEffects())
+    return false;
+
+  // If the instruction could modify memory, or there may be some intervening
+  // store between the two, we can't consider them to be equal.
+  if (TDef->mayLoadOrStore() && !TDef->isDereferenceableInvariantLoad(nullptr))
+    return false;
+
+  // We also can't guarantee that they are the same if, for example, the
+  // instructions are both a copy from a physical reg, because some other
+  // instruction may have modified the value in that reg between the two
+  // defining insts.
+  if (any_of(TDef->uses(), [](const MachineOperand &MO) {
+        return MO.isReg() && MO.getReg().isPhysical();
+      }))
+    return false;
+
+  // Check whether the two defining instructions produce the same value(s).
+  if (!TII->produceSameValue(*TDef, *FDef, &MRI))
+    return false;
+
+  // Further, check that the two defs come from corresponding operands.
+  return operandIndex(*TDef, TReg) == operandIndex(*FDef, FReg);
+}
+
 /// replacePHIInstrs - Completely replace PHI instructions with selects.
 /// This is possible when the only Tail predecessors are the if-converted
 /// blocks.
@@ -571,7 +622,15 @@
     PHIInfo &PI = PHIs[i];
     LLVM_DEBUG(dbgs() << "If-converting " << *PI.PHI);
     Register DstReg = PI.PHI->getOperand(0).getReg();
-    TII->insertSelect(*Head, FirstTerm, HeadDL, DstReg, Cond, PI.TReg, PI.FReg);
+    if (hasSameValue(*MRI, TII, PI.TReg, PI.FReg)) {
+      // We do not need the select instruction if both incoming values are
+      // equal, but we do need a COPY.
+      BuildMI(*Head, FirstTerm, HeadDL, TII->get(TargetOpcode::COPY), DstReg)
+          .addReg(PI.TReg);
+    } else {
+      TII->insertSelect(*Head, FirstTerm, HeadDL, DstReg, Cond, PI.TReg,
+                        PI.FReg);
+    }
     LLVM_DEBUG(dbgs() << "          --> " << *std::prev(FirstTerm));
     PI.PHI->eraseFromParent();
     PI.PHI = nullptr;
@@ -592,7 +651,7 @@
     unsigned DstReg = 0;
 
     LLVM_DEBUG(dbgs() << "If-converting " << *PI.PHI);
-    if (PI.TReg == PI.FReg) {
+    if (hasSameValue(*MRI, TII, PI.TReg, PI.FReg)) {
       // We do not need the select instruction if both incoming values are
       // equal.
       DstReg = PI.TReg;
diff --git a/llvm/test/CodeGen/AArch64/early-ifcvt-same-value.mir b/llvm/test/CodeGen/AArch64/early-ifcvt-same-value.mir
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/early-ifcvt-same-value.mir
@@ -0,0 +1,250 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=aarch64-- -run-pass=early-ifcvt -stress-early-ifcvt -verify-machineinstrs %s -o - | FileCheck %s
+
+---
+name:            fmov0
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: fpr32, preferred-register: '' }
+  - { id: 1, class: fpr32, preferred-register: '' }
+  - { id: 2, class: fpr32, preferred-register: '' }
+  - { id: 3, class: fpr32, preferred-register: '' }
+  - { id: 4, class: fpr32, preferred-register: '' }
+  - { id: 5, class: gpr32common, preferred-register: '' }
+  - { id: 6, class: gpr32, preferred-register: '' }
+  - { id: 7, class: fpr32, preferred-register: '' }
+  - { id: 8, class: fpr32, preferred-register: '' }
+liveins:
+  - { reg: '$s1', virtual-reg: '%4' }
+  - { reg: '$w0', virtual-reg: '%5' }
+body:             |
+  ; CHECK-LABEL: name: fmov0
+  ; CHECK: bb.0.entry:
+  ; CHECK:   liveins: $s1, $w0
+  ; CHECK:   [[COPY:%[0-9]+]]:gpr32common = COPY $w0
+  ; CHECK:   [[COPY1:%[0-9]+]]:fpr32 = COPY $s1
+  ; CHECK:   [[SUBSWri:%[0-9]+]]:gpr32 = SUBSWri [[COPY]], 1, 0, implicit-def $nzcv
+  ; CHECK:   [[FMOVS0_:%[0-9]+]]:fpr32 = FMOVS0
+  ; CHECK:   [[FMOVS0_1:%[0-9]+]]:fpr32 = FMOVS0
+  ; CHECK:   [[COPY2:%[0-9]+]]:fpr32 = COPY [[FMOVS0_]]
+  ; CHECK:   $s0 = COPY [[COPY2]]
+  ; CHECK:   RET_ReallyLR implicit $s0
+  bb.0.entry:
+    successors: %bb.1, %bb.2
+    liveins: $s1, $w0
+
+    %5:gpr32common = COPY $w0
+    %4:fpr32 = COPY $s1
+    %6:gpr32 = SUBSWri %5, 1, 0, implicit-def $nzcv
+    Bcc 1, %bb.2, implicit $nzcv
+    B %bb.1
+
+  bb.1:
+    successors: %bb.3
+
+    %0:fpr32 = FMOVS0
+    B %bb.3
+
+  bb.2:
+    successors: %bb.3
+
+    %1:fpr32 = FMOVS0
+
+  bb.3:
+    %2:fpr32 = PHI %1, %bb.2, %0, %bb.1
+    $s0 = COPY %2
+    RET_ReallyLR implicit $s0
+
+...
+---
+name:            fmov0_extrapred
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: fpr32, preferred-register: '' }
+  - { id: 1, class: fpr32, preferred-register: '' }
+  - { id: 2, class: fpr32, preferred-register: '' }
+  - { id: 3, class: fpr32, preferred-register: '' }
+  - { id: 4, class: fpr32, preferred-register: '' }
+  - { id: 5, class: gpr32common, preferred-register: '' }
+  - { id: 6, class: gpr32, preferred-register: '' }
+  - { id: 7, class: fpr32, preferred-register: '' }
+  - { id: 8, class: fpr32, preferred-register: '' }
+liveins:
+  - { reg: '$s1', virtual-reg: '%4' }
+  - { reg: '$w0', virtual-reg: '%5' }
+body:             |
+  ; CHECK-LABEL: name: fmov0_extrapred
+  ; CHECK: bb.0.entry:
+  ; CHECK:   successors: %bb.4(0x80000000)
+  ; CHECK:   liveins: $s1, $w0
+  ; CHECK:   [[COPY:%[0-9]+]]:gpr32common = COPY $w0
+  ; CHECK:   [[COPY1:%[0-9]+]]:fpr32 = COPY $s1
+  ; CHECK:   [[SUBSWri:%[0-9]+]]:gpr32 = SUBSWri [[COPY]], 1, 0, implicit-def $nzcv
+  ; CHECK:   [[FMOVS0_:%[0-9]+]]:fpr32 = FMOVS0
+  ; CHECK:   [[FMOVS0_1:%[0-9]+]]:fpr32 = FMOVS0
+  ; CHECK:   B %bb.4
+  ; CHECK: bb.1:
+  ; CHECK:   successors: %bb.4(0x80000000)
+  ; CHECK:   [[DEF:%[0-9]+]]:fpr32 = IMPLICIT_DEF
+  ; CHECK:   B %bb.4
+  ; CHECK: bb.4:
+  ; CHECK:   [[PHI:%[0-9]+]]:fpr32 = PHI [[FMOVS0_]], %bb.0, [[DEF]], %bb.1
+  ; CHECK:   $s0 = COPY [[PHI]]
+  ; CHECK:   RET_ReallyLR implicit $s0
+  bb.0.entry:
+    successors: %bb.1, %bb.2
+    liveins: $s1, $w0
+
+    %5:gpr32common = COPY $w0
+    %4:fpr32 = COPY $s1
+    %6:gpr32 = SUBSWri %5, 1, 0, implicit-def $nzcv
+    Bcc 1, %bb.2, implicit $nzcv
+    B %bb.1
+
+  bb.4:
+    successors: %bb.3
+
+    ; Make sure we also handle the case when there are extra predecessors on
+    ; the tail block.
+    %3:fpr32 = IMPLICIT_DEF
+    B %bb.3
+
+  bb.1:
+    successors: %bb.3
+
+    %0:fpr32 = FMOVS0
+    B %bb.3
+
+  bb.2:
+    successors: %bb.3
+
+    %1:fpr32 = FMOVS0
+
+  bb.3:
+    %2:fpr32 = PHI %1, %bb.2, %0, %bb.1, %3, %bb.4
+    $s0 = COPY %2
+    RET_ReallyLR implicit $s0
+
+...
+---
+name:            copy_physreg
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: fpr32, preferred-register: '' }
+  - { id: 1, class: fpr32, preferred-register: '' }
+  - { id: 2, class: fpr32, preferred-register: '' }
+  - { id: 3, class: fpr32, preferred-register: '' }
+  - { id: 4, class: fpr32, preferred-register: '' }
+  - { id: 5, class: gpr32common, preferred-register: '' }
+  - { id: 6, class: gpr32, preferred-register: '' }
+  - { id: 7, class: fpr32, preferred-register: '' }
+  - { id: 8, class: fpr32, preferred-register: '' }
+  - { id: 9, class: fpr32, preferred-register: '' }
+  - { id: 10, class: fpr32, preferred-register: '' }
+liveins:
+  - { reg: '$s1', virtual-reg: '%4' }
+  - { reg: '$w0', virtual-reg: '%5' }
+body:             |
+  ; CHECK-LABEL: name: copy_physreg
+  ; CHECK: bb.0.entry:
+  ; CHECK:   liveins: $s1, $w0
+  ; CHECK:   [[COPY:%[0-9]+]]:gpr32common = COPY $w0
+  ; CHECK:   [[COPY1:%[0-9]+]]:fpr32 = COPY $s1
+  ; CHECK:   [[SUBSWri:%[0-9]+]]:gpr32 = SUBSWri [[COPY]], 1, 0, implicit-def $nzcv
+  ; CHECK:   [[DEF:%[0-9]+]]:fpr32 = IMPLICIT_DEF implicit-def $s1
+  ; CHECK:   [[COPY2:%[0-9]+]]:fpr32 = COPY $s1
+  ; CHECK:   [[DEF1:%[0-9]+]]:fpr32 = IMPLICIT_DEF implicit-def $s1
+  ; CHECK:   [[COPY3:%[0-9]+]]:fpr32 = COPY $s1
+  ; CHECK:   [[FCSELSrrr:%[0-9]+]]:fpr32 = FCSELSrrr [[COPY2]], [[COPY3]], 1, implicit $nzcv
+  ; CHECK:   $s0 = COPY [[FCSELSrrr]]
+  ; CHECK:   RET_ReallyLR implicit $s0
+  bb.0.entry:
+    successors: %bb.1, %bb.2
+    liveins: $s1, $w0
+
+    %5:gpr32common = COPY $w0
+    %4:fpr32 = COPY $s1
+    %6:gpr32 = SUBSWri %5, 1, 0, implicit-def $nzcv
+    Bcc 1, %bb.2, implicit $nzcv
+    B %bb.1
+
+  bb.1:
+    successors: %bb.3
+
+    %9:fpr32 = IMPLICIT_DEF implicit-def $s1
+    %0:fpr32 = COPY $s1
+    B %bb.3
+
+  bb.2:
+    successors: %bb.3
+
+    %10:fpr32 = IMPLICIT_DEF implicit-def $s1
+    %1:fpr32 = COPY $s1
+
+  bb.3:
+    %2:fpr32 = PHI %1, %bb.2, %0, %bb.1
+    $s0 = COPY %2
+    RET_ReallyLR implicit $s0
+
+...
+---
+name:            same_def_different_operand
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: fpr32, preferred-register: '' }
+  - { id: 1, class: fpr32, preferred-register: '' }
+  - { id: 2, class: gpr64common, preferred-register: '' }
+  - { id: 3, class: fpr32, preferred-register: '' }
+  - { id: 4, class: fpr32, preferred-register: '' }
+  - { id: 5, class: gpr32common, preferred-register: '' }
+  - { id: 6, class: gpr32, preferred-register: '' }
+  - { id: 7, class: fpr32, preferred-register: '' }
+  - { id: 8, class: fpr32, preferred-register: '' }
+  - { id: 9, class: gpr64common, preferred-register: '' }
+  - { id: 10, class: gpr64, preferred-register: '' }
+  - { id: 11, class: gpr64common, preferred-register: '' }
+liveins:
+  - { reg: '$s1', virtual-reg: '%4' }
+  - { reg: '$w0', virtual-reg: '%5' }
+  - { reg: '$x2', virtual-reg: '%9' }
+body:             |
+  ; CHECK-LABEL: name: same_def_different_operand
+  ; CHECK: bb.0.entry:
+  ; CHECK:   liveins: $s1, $w0, $x2
+  ; CHECK:   [[COPY:%[0-9]+]]:gpr64common = COPY $x0
+  ; CHECK:   early-clobber %11:gpr64common, %10:gpr64 = LDRXpre [[COPY]], 16
+  ; CHECK:   [[COPY1:%[0-9]+]]:gpr32common = COPY $w0
+  ; CHECK:   [[COPY2:%[0-9]+]]:fpr32 = COPY $s1
+  ; CHECK:   [[SUBSWri:%[0-9]+]]:gpr32 = SUBSWri [[COPY1]], 1, 0, implicit-def $nzcv
+  ; CHECK:   [[CSELXr:%[0-9]+]]:gpr64common = CSELXr %11, %10, 1, implicit $nzcv
+  ; CHECK:   $x2 = COPY [[CSELXr]]
+  ; CHECK:   RET_ReallyLR implicit $x2
+  bb.0.entry:
+    successors: %bb.1, %bb.2
+    liveins: $s1, $w0, $x2
+
+    %9:gpr64common = COPY $x0
+    early-clobber %11:gpr64common, %10:gpr64 = LDRXpre %9:gpr64common, 16
+
+    %5:gpr32common = COPY $w0
+    %4:fpr32 = COPY $s1
+    %6:gpr32 = SUBSWri %5, 1, 0, implicit-def $nzcv
+    Bcc 1, %bb.2, implicit $nzcv
+    B %bb.1
+
+  bb.1:
+    successors: %bb.3
+
+    B %bb.3
+
+  bb.2:
+    successors: %bb.3
+
+    B %bb.3
+
+  bb.3:
+    %2:gpr64common = PHI %11, %bb.2, %10, %bb.1
+    $x2 = COPY %2
+    RET_ReallyLR implicit $x2
+
+...