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
@@ -39,7 +39,7 @@
 STATISTIC(NumNoUnwind, "Number of functions inferred as nounwind");
 STATISTIC(NumNoCapture, "Number of arguments inferred as nocapture");
 STATISTIC(NumWriteOnlyArg, "Number of arguments inferred as writeonly");
-STATISTIC(NumSExtArg, "Number of arguments inferred as signext");
+STATISTIC(NumExtArg, "Number of arguments inferred as signext/zeroext.");
 STATISTIC(NumReadOnlyArg, "Number of arguments inferred as readonly");
 STATISTIC(NumNoAlias, "Number of function returns inferred as noalias");
 STATISTIC(NumNoUndef, "Number of function returns inferred as noundef returns");
@@ -147,11 +147,13 @@
   return true;
 }
 
-static bool setSignExtendedArg(Function &F, unsigned ArgNo) {
- if (F.hasParamAttribute(ArgNo, Attribute::SExt))
+static bool setArgExtAttr(Function &F, unsigned ArgNo,
+                          const TargetLibraryInfo &TLI, bool Signed = true) {
+  Attribute::AttrKind ExtAttr = TLI.getExtAttrForI32Param(Signed);
+  if (ExtAttr == Attribute::None || F.hasParamAttribute(ArgNo, ExtAttr))
     return false;
-  F.addParamAttr(ArgNo, Attribute::SExt);
-  ++NumSExtArg;
+  F.addParamAttr(ArgNo, ExtAttr);
+  ++NumExtArg;
   return true;
 }
 
@@ -829,6 +831,7 @@
   case LibFunc_putchar:
   case LibFunc_putchar_unlocked:
     Changed |= setRetAndArgsNoUndef(F);
+    Changed |= setArgExtAttr(F, 0, TLI);
     Changed |= setDoesNotThrow(F);
     return Changed;
   case LibFunc_popen:
@@ -1049,7 +1052,7 @@
   case LibFunc_ldexp:
   case LibFunc_ldexpf:
   case LibFunc_ldexpl:
-    Changed |= setSignExtendedArg(F, 1);
+    Changed |= setArgExtAttr(F, 1, TLI);
     Changed |= setWillReturn(F);
     return Changed;
   case LibFunc_abs:
diff --git a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
--- a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
+++ b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
@@ -3,6 +3,7 @@
 ; RUN: opt < %s -mtriple=x86_64-apple-macosx10.8.0 -inferattrs -S | FileCheck --match-full-lines --check-prefixes=CHECK,CHECK-KNOWN,CHECK-NOLINUX,CHECK-OPEN,CHECK-DARWIN %s
 ; RUN: opt < %s -mtriple=x86_64-unknown-linux-gnu -inferattrs -S | FileCheck --match-full-lines --check-prefixes=CHECK,CHECK-KNOWN,CHECK-LINUX %s
 ; RUN: opt < %s -mtriple=nvptx -inferattrs -S | FileCheck --match-full-lines --check-prefixes=CHECK-NOLINUX,CHECK-NVPTX %s
+; RUN: opt < %s -mtriple=s390x-linux-gnu -inferattrs -S | FileCheck --check-prefixes=CHECK-SYSTEMZ %s
 
 declare i32 @__nvvm_reflect(i8*)
 ; CHECK-NVPTX: declare noundef i32 @__nvvm_reflect(i8* noundef) [[NOFREE_NOUNWIND_READNONE:#[0-9]+]]
@@ -590,13 +591,15 @@
 ; CHECK: declare noundef i32 @lchown(i8* nocapture noundef readonly, i32 noundef, i32 noundef) [[NOFREE_NOUNWIND]]
 declare i32 @lchown(i8*, i32, i32)
 
-; CHECK: declare double @ldexp(double, i32 signext) [[NOFREE_WILLRETURN:#[0-9]+]]
+; CHECK: declare double @ldexp(double, i32) [[NOFREE_WILLRETURN:#[0-9]+]]
+; CHECK-SYSTEMZ: declare double @ldexp(double, i32 signext)
 declare double @ldexp(double, i32)
 
-; CHECK: declare float @ldexpf(float, i32 signext) [[NOFREE_WILLRETURN]]
+; CHECK: declare float @ldexpf(float, i32) [[NOFREE_WILLRETURN]]
+; CHECK-SYSTEMZ: declare float @ldexpf(float, i32 signext)
 declare float @ldexpf(float, i32)
 
-; CHECK: declare x86_fp80 @ldexpl(x86_fp80, i32 signext) [[NOFREE_WILLRETURN]]
+; CHECK: declare x86_fp80 @ldexpl(x86_fp80, i32) [[NOFREE_WILLRETURN]]
 declare x86_fp80 @ldexpl(x86_fp80, i32)
 
 ; CHECK: declare i64 @llabs(i64) [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
@@ -753,10 +756,12 @@
 declare i32 @putc(i32, %opaque*)
 
 ; CHECK: declare noundef i32 @putchar(i32 noundef) [[NOFREE_NOUNWIND]]
+; CHECK-SYSTEMZ: declare noundef i32 @putchar(i32 noundef signext)
 declare i32 @putchar(i32)
 
 ; CHECK-KNOWN: declare noundef i32 @putchar_unlocked(i32 noundef) [[NOFREE_NOUNWIND]]
 ; CHECK-UNKNOWN: declare i32 @putchar_unlocked(i32){{$}}
+; CHECK-SYSTEMZ: declare noundef i32 @putchar_unlocked(i32 noundef signext)
 declare i32 @putchar_unlocked(i32)
 
 ; CHECK: declare noundef i32 @puts(i8* nocapture noundef readonly) [[NOFREE_NOUNWIND]]