diff --git a/lib/CodeGen/CodeGenPrepare.cpp b/lib/CodeGen/CodeGenPrepare.cpp
index 0a711cca4db..47c18926749 100644
--- a/lib/CodeGen/CodeGenPrepare.cpp
+++ b/lib/CodeGen/CodeGenPrepare.cpp
@@ -2069,9 +2069,13 @@ Value *TypePromotionHelper::promoteOperandForOther(
     if (!ExtForOpnd) {
       // If yes, create a new one.
       DEBUG(dbgs() << "More operands to ext\n");
-      ExtForOpnd =
-          cast<Instruction>(IsSExt ? TPT.createSExt(Ext, Opnd, Ext->getType())
-                                   : TPT.createZExt(Ext, Opnd, Ext->getType()));
+      Value *ValForExtOpnd = IsSExt ? TPT.createSExt(Ext, Opnd, Ext->getType())
+        : TPT.createZExt(Ext, Opnd, Ext->getType());
+      if (!isa<Instruction>(ValForExtOpnd)) {
+        TPT.setOperand(ExtOpnd, OpIdx, ValForExtOpnd);
+        continue;
+      }
+      ExtForOpnd = cast<Instruction>(ValForExtOpnd);
       ++CreatedInsts;
     }
     if (Exts)
diff --git a/test/CodeGen/X86/codegen-prepare-extload.ll b/test/CodeGen/X86/codegen-prepare-extload.ll
index f607a6f3569..9b27c33a80f 100644
--- a/test/CodeGen/X86/codegen-prepare-extload.ll
+++ b/test/CodeGen/X86/codegen-prepare-extload.ll
@@ -336,3 +336,28 @@ entry:
   %b = zext <2 x i32> %a to <2 x i64>
   ret void
 }
+
+@a = common global i32 0, align 4
+@c = common global [2 x i32] zeroinitializer, align 4
+
+; PR21978.
+; Make sure we support promotion of operands that produces a Value as opposed
+; to an instruction.
+; This used to cause a crash.
+; OPTALL-LABEL: @promotionOfArgEndsUpInValue
+; OPTALL: [[LD:%[a-zA-Z_0-9-]+]] = load i16* %addr
+
+; OPT-NEXT: [[SEXT:%[a-zA-Z_0-9-]+]] = sext i16 [[LD]] to i32
+; OPT-NEXT: [[RES:%[a-zA-Z_0-9-]+]] = add nuw nsw i32 [[SEXT]], zext (i1 icmp ne (i32* getelementptr inbounds ([2 x i32]* @c, i64 0, i64 1), i32* @a) to i32)
+;
+; DISABLE-NEXT: [[ADD:%[a-zA-Z_0-9-]+]] = add nuw nsw i16 [[LD]], zext (i1 icmp ne (i32* getelementptr inbounds ([2 x i32]* @c, i64 0, i64 1), i32* @a) to i16)
+; DISABLE-NEXT: [[RES:%[a-zA-Z_0-9-]+]] = sext i16 [[ADD]] to i32
+;
+; OPTALL-NEXT: ret i32 [[RES]]
+define i32 @promotionOfArgEndsUpInValue(i16* %addr) {
+entry:
+  %val = load i16* %addr
+  %add = add nuw nsw i16 %val, zext (i1 icmp ne (i32* getelementptr inbounds ([2 x i32]* @c, i64 0, i64 1), i32* @a) to i16)
+  %conv3 = sext i16 %add to i32
+  ret i32 %conv3
+}