Index: lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -2196,6 +2196,7 @@
       if (UnsafeFPShrink && hasFloatVersion(FuncName))
         return optimizeUnaryDoubleFP(CI, Builder, true);
       return nullptr;
+    case LibFunc::copysign:
     case LibFunc::fmin:
     case LibFunc::fmax:
       if (hasFloatVersion(FuncName))
Index: test/Transforms/InstCombine/float-shrink-compare.ll
===================================================================
--- test/Transforms/InstCombine/float-shrink-compare.ll
+++ test/Transforms/InstCombine/float-shrink-compare.ll
@@ -234,8 +234,22 @@
 ; CHECK-NEXT: fcmp oeq float %fminf, %y
 }
 
+define i32 @test20(float %x, float %y, float %z) nounwind uwtable {
+  %1 = fpext float %x to double
+  %2 = fpext float %y to double
+  %3 = call double @copysign(double %1, double %2) nounwind
+  %4 = fpext float %z to double
+  %5 = fcmp oeq double %3, %4
+  %6 = zext i1 %5 to i32
+  ret i32 %6
+; CHECK-LABEL: @test20(
+; CHECK-NEXT: %copysignf = call float @copysignf(float %x, float %y)
+; CHECK-NEXT: fcmp oeq float %copysignf, %z
+}
+
 declare double @fabs(double) nounwind readnone
 declare double @ceil(double) nounwind readnone
+declare double @copysign(double, double) nounwind readnone
 declare double @floor(double) nounwind readnone
 declare double @nearbyint(double) nounwind readnone
 declare double @rint(double) nounwind readnone