Index: llvm/lib/Transforms/Utils/BuildLibCalls.cpp
===================================================================
--- llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -1216,6 +1216,13 @@
   return B.CreateBitCast(V, B.getInt8PtrTy(AS), "cstr");
 }
 
+static void setCallingConvAndAttrs(CallInst *&CI, const Value *V) {
+  if (const Function *F = dyn_cast<Function>(V)) {
+    CI->setCallingConv(F->getCallingConv());
+    CI->setAttributes(F->getAttributes());
+  }
+}
+
 static Value *emitLibCall(LibFunc TheLibFunc, Type *ReturnType,
                           ArrayRef<Type *> ParamTypes,
                           ArrayRef<Value *> Operands, IRBuilderBase &B,
@@ -1230,9 +1237,7 @@
   FunctionCallee Callee = M->getOrInsertFunction(FuncName, FuncType);
   inferLibFuncAttributes(M, FuncName, *TLI);
   CallInst *CI = B.CreateCall(Callee, Operands, FuncName);
-  if (const Function *F =
-          dyn_cast<Function>(Callee.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
+  setCallingConvAndAttrs(CI, Callee.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1312,9 +1317,7 @@
   Dst = castToCStr(Dst, B);
   Src = castToCStr(Src, B);
   CallInst *CI = B.CreateCall(MemCpy, {Dst, Src, Len, ObjSize});
-  if (const Function *F =
-          dyn_cast<Function>(MemCpy.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
+  setCallingConvAndAttrs(CI, MemCpy.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1456,10 +1459,7 @@
   CI->setAttributes(Attrs.removeAttribute(B.getContext(),
                                           AttributeList::FunctionIndex,
                                           Attribute::Speculatable));
-  if (const Function *F =
-          dyn_cast<Function>(Callee.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
+  setCallingConvAndAttrs(CI, Callee.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1501,10 +1501,7 @@
   CI->setAttributes(Attrs.removeAttribute(B.getContext(),
                                           AttributeList::FunctionIndex,
                                           Attribute::Speculatable));
-  if (const Function *F =
-          dyn_cast<Function>(Callee.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
+  setCallingConvAndAttrs(CI, Callee.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1548,9 +1545,7 @@
                               "chari"),
                               PutCharName);
 
-  if (const Function *F =
-          dyn_cast<Function>(PutChar.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
+  setCallingConvAndAttrs(CI, PutChar.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1565,9 +1560,7 @@
       M->getOrInsertFunction(PutsName, B.getInt32Ty(), B.getInt8PtrTy());
   inferLibFuncAttributes(M, PutsName, *TLI);
   CallInst *CI = B.CreateCall(PutS, castToCStr(Str, B), PutsName);
-  if (const Function *F =
-          dyn_cast<Function>(PutS.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
+  setCallingConvAndAttrs(CI, PutS.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1585,10 +1578,7 @@
   Char = B.CreateIntCast(Char, B.getInt32Ty(), /*isSigned*/true,
                          "chari");
   CallInst *CI = B.CreateCall(F, {Char, File}, FPutcName);
-
-  if (const Function *Fn =
-          dyn_cast<Function>(F.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(Fn->getCallingConv());
+  setCallingConvAndAttrs(CI, F.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1604,10 +1594,7 @@
   if (File->getType()->isPointerTy())
     inferLibFuncAttributes(M, FPutsName, *TLI);
   CallInst *CI = B.CreateCall(F, {castToCStr(Str, B), File}, FPutsName);
-
-  if (const Function *Fn =
-          dyn_cast<Function>(F.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(Fn->getCallingConv());
+  setCallingConvAndAttrs(CI, F.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1628,10 +1615,7 @@
   CallInst *CI =
       B.CreateCall(F, {castToCStr(Ptr, B), Size,
                        ConstantInt::get(DL.getIntPtrType(Context), 1), File});
-
-  if (const Function *Fn =
-          dyn_cast<Function>(F.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(Fn->getCallingConv());
+  setCallingConvAndAttrs(CI, F.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1647,11 +1631,7 @@
                                                  DL.getIntPtrType(Context));
   inferLibFuncAttributes(M, MallocName, *TLI);
   CallInst *CI = B.CreateCall(Malloc, Num, MallocName);
-
-  if (const Function *F =
-          dyn_cast<Function>(Malloc.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
+  setCallingConvAndAttrs(CI, Malloc.getCallee()->stripPointerCasts());
   return CI;
 }
 
@@ -1668,10 +1648,6 @@
       CallocName, Attrs, B.getInt8PtrTy(), PtrType, PtrType);
   inferLibFuncAttributes(M, CallocName, TLI);
   CallInst *CI = B.CreateCall(Calloc, {Num, Size}, CallocName);
-
-  if (const auto *F =
-          dyn_cast<Function>(Calloc.getCallee()->stripPointerCasts()))
-    CI->setCallingConv(F->getCallingConv());
-
+  setCallingConvAndAttrs(CI, Calloc.getCallee()->stripPointerCasts());
   return CI;
 }
Index: llvm/test/Transforms/InstCombine/libcall-param-attrs.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/libcall-param-attrs.ll
@@ -0,0 +1,30 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+; REQUIRES: systemz-registered-target
+;
+; Check that instcombiner creates libcalls with parameter extensions per the
+; prototype.
+
+declare dso_local i8* @strchr(i8*, i32) local_unnamed_addr #1
+declare dso_local i8* @memchr(i8*, i32 signext, i64)
+declare void @llvm.assume(i1 noundef)
+@0 = private unnamed_addr constant [21 x i8] c"000000000000000000000", align 2
+define void @fun0(i32 %arg1) {
+; CHECK: define void @fun0
+; CHECK: call i8* @memchr{{.*}}, i32 signext %arg1, i64 22)
+bb:
+  %i = call i8* @strchr(i8* getelementptr inbounds ([21 x i8], [21 x i8]* @0, i64 0, i64 0), i32 signext %arg1)
+  %i3 = icmp ne i8* %i, null
+  call void @llvm.assume(i1 %i3)
+  ret void
+}
+
+declare dso_local double @pow(double, double)
+define void @fun1(i32* %i5) {
+; CHECK: define void @fun1
+; CHECK: call double @ldexp{{.*}}, i32 signext %i19)
+bb:
+  %i19 = load i32, i32* %i5, align 4
+  %i20 = sitofp i32 %i19 to double
+  %i21 = call double @pow(double 2.000000e+00, double %i20)
+  ret void
+}