diff --git a/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp b/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
--- a/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -537,6 +537,24 @@
     MachineOperand &PMO = MI.getOperand(PIdx);
     PMO.setImm(Pred[0].getImm());
     MI.getOperand(PIdx+1).setReg(Pred[1].getReg());
+
+    // Thumb 1 arithmetic instructions do not set CPSR when executed inside an
+    // IT block. This affects how they are printed.
+    const MCInstrDesc &MCID = MI.getDesc();
+    if (MCID.TSFlags & ARMII::ThumbArithFlagSetting) {
+      // Find the optional-def operand (cc_out).
+      unsigned OpNo;
+      for (OpNo = 0;
+           !MCID.OpInfo[OpNo].isOptionalDef() && OpNo < MCID.NumOperands;
+           ++OpNo)
+        ;
+      assert(MCID.OpInfo[OpNo].isOptionalDef());
+      assert((MI.getOperand(OpNo).isDead() ||
+              MI.getOperand(OpNo).getReg() != ARM::CPSR) &&
+             "if conversion tried to stop defining used CPSR");
+      MI.getOperand(OpNo).setReg(ARM::NoRegister);
+    }
+
     return true;
   }
   return false;
diff --git a/llvm/lib/Target/ARM/ARMInstrFormats.td b/llvm/lib/Target/ARM/ARMInstrFormats.td
--- a/llvm/lib/Target/ARM/ARMInstrFormats.td
+++ b/llvm/lib/Target/ARM/ARMInstrFormats.td
@@ -403,8 +403,9 @@
   bit isUnaryDataProc = 0;
   bit canXformTo16Bit = 0;
   // The instruction is a 16-bit flag setting Thumb instruction. Used
-  // by the parser to determine whether to require the 'S' suffix on the
-  // mnemonic (when not in an IT block) or preclude it (when in an IT block).
+  // by the parser and if-converter to determine whether to require the 'S'
+  // suffix on the mnemonic (when not in an IT block) or preclude it (when
+  // in an IT block).
   bit thumbArithFlagSetting = 0;
 
   bit validForTailPredication = 0;
diff --git a/llvm/test/CodeGen/Thumb2/ifcvt-rescan-diamonds.ll b/llvm/test/CodeGen/Thumb2/ifcvt-rescan-diamonds.ll
--- a/llvm/test/CodeGen/Thumb2/ifcvt-rescan-diamonds.ll
+++ b/llvm/test/CodeGen/Thumb2/ifcvt-rescan-diamonds.ll
@@ -22,7 +22,8 @@
 ; CHECK-NEXT: it eq
 ; CHECK-NEXT: ldreq
 ; CHECK-NEXT: it ne
-; CHECK-NEXT: movsne
+  ; N.b. 16-bit mov instruction in IT block does not set flags.
+; CHECK-NEXT: movne
 ; CHECK-NEXT: mvns
 ; CHECK-NEXT: b
 cond.true77:                                      ; preds = %while.cond38