diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -1501,6 +1501,12 @@
   CI->setAttributes(Attrs.removeAttribute(B.getContext(),
                                           AttributeList::FunctionIndex,
                                           Attribute::Speculatable));
+  for (int I = 0, E = Callee.getFunctionType()->getNumParams(); I != E; ++I) {
+    for (const auto &A :
+         CI->getCalledFunction()->getAttributes().getParamAttributes(I)) {
+      CI->addParamAttr(I, A);
+    }
+  }
   if (const Function *F =
           dyn_cast<Function>(Callee.getCallee()->stripPointerCasts()))
     CI->setCallingConv(F->getCallingConv());
diff --git a/llvm/test/Transforms/InstCombine/pow_fp_int.ll b/llvm/test/Transforms/InstCombine/pow_fp_int.ll
--- a/llvm/test/Transforms/InstCombine/pow_fp_int.ll
+++ b/llvm/test/Transforms/InstCombine/pow_fp_int.ll
@@ -51,7 +51,7 @@
 
 define double @pow_sitofp_double_const_base_2_fast(i32 %x) {
 ; CHECK-LABEL: @pow_sitofp_double_const_base_2_fast(
-; CHECK-NEXT:    [[LDEXPF:%.*]] = call afn float @ldexpf(float 1.000000e+00, i32 [[X:%.*]])
+; CHECK-NEXT:    [[LDEXPF:%.*]] = call afn float @ldexpf(float 1.000000e+00, i32 signext [[X:%.*]])
 ; CHECK-NEXT:    [[RES:%.*]] = fpext float [[LDEXPF]] to double
 ; CHECK-NEXT:    ret double [[RES]]
 ;
@@ -78,7 +78,7 @@
 define double @pow_uitofp_const_base_2_fast(i31 %x) {
 ; CHECK-LABEL: @pow_uitofp_const_base_2_fast(
 ; CHECK-NEXT:    [[TMP1:%.*]] = zext i31 [[X:%.*]] to i32
-; CHECK-NEXT:    [[LDEXPF:%.*]] = call afn float @ldexpf(float 1.000000e+00, i32 [[TMP1]])
+; CHECK-NEXT:    [[LDEXPF:%.*]] = call afn float @ldexpf(float 1.000000e+00, i32 signext [[TMP1]])
 ; CHECK-NEXT:    [[RES:%.*]] = fpext float [[LDEXPF]] to double
 ; CHECK-NEXT:    ret double [[RES]]
 ;
@@ -343,7 +343,7 @@
 
 define double @pow_sitofp_const_base_2_no_fast(i32 %x) {
 ; CHECK-LABEL: @pow_sitofp_const_base_2_no_fast(
-; CHECK-NEXT:    [[LDEXPF:%.*]] = call float @ldexpf(float 1.000000e+00, i32 [[X:%.*]])
+; CHECK-NEXT:    [[LDEXPF:%.*]] = call float @ldexpf(float 1.000000e+00, i32 signext [[X:%.*]])
 ; CHECK-NEXT:    [[RES:%.*]] = fpext float [[LDEXPF]] to double
 ; CHECK-NEXT:    ret double [[RES]]
 ;
diff --git a/llvm/test/Transforms/InstCombine/simplify-libcalls.ll b/llvm/test/Transforms/InstCombine/simplify-libcalls.ll
--- a/llvm/test/Transforms/InstCombine/simplify-libcalls.ll
+++ b/llvm/test/Transforms/InstCombine/simplify-libcalls.ll
@@ -189,7 +189,7 @@
 }
 define double @fake_ldexp(i32 %x) {
 ; CHECK-LABEL: @fake_ldexp(
-; CHECK-NEXT:    [[Z:%.*]] = call double @ldexp(double 1.0{{.*}}, i32 %x)
+; CHECK-NEXT:    [[Z:%.*]] = call double @ldexp(double 1.0{{.*}}, i32 signext %x)
 ; CHECK-NEXT:    ret double [[Z]]
 
   %y = sitofp i32 %x to double
@@ -197,6 +197,8 @@
   ret double %z
 }
 
+; CHECK: declare double @ldexp(double, i32 signext)
+
 
 attributes #0 = { nobuiltin }
 attributes #1 = { builtin }