[SystemZ] Make LibFunc_bcmp unavailable

[jonpa]

Summary

Memcmp has hardware support on SystemZ, so there is no need or benefit of sometimes using bcmp .

This patch makes bcmp unavailable on SystemZ, so that memcmp:s are not replaced by calls to it.

[jonpa]

Replaced by https://reviews.llvm.org/D87988

llvm/lib/Analysis/TargetLibraryInfo.cpp

if (!hasSinCosPiStret(T)) {
     TLI.setUnavailable(LibFunc_sinpi);
     TLI.setUnavailable(LibFunc_sinpif);
     TLI.setUnavailable(LibFunc_cospi);
     TLI.setUnavailable(LibFunc_cospif);
     TLI.setUnavailable(LibFunc_sincospi_stret);
     TLI.setUnavailable(LibFunc_sincospif_stret);
   }
 
-  if (!hasBcmp(T))
+  // Memcmp has hardware support on SystemZ, so no need for bcmp.
+  if (!hasBcmp(T) || T.isSystemZ())
     TLI.setUnavailable(LibFunc_bcmp);
 
   if (T.isMacOSX() && T.getArch() == Triple::x86 &&
       !T.isMacOSXVersionLT(10, 7)) {
     // x86-32 OSX has a scheme where fwrite and fputs (and some other functions
     // we don't care about) have two versions; on recent OSX, the one we want
     // has a $UNIX2003 suffix. The two implementations are identical except
     // for the return value in some edge cases.  However, we don't want to

llvm/test/Transforms/InstCombine/memcmp-3.ll

+; RUN: opt -S -O3 < %s | FileCheck %s
+; REQUIRES: systemz-registered-target
+;
+; Test that memcmp is not replaced with bcmp on SystemZ.
+
+target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
+target triple = "s390x-unknown-linux-gnu"
+
+; CHECK-LABEL: @fun
+; CHECK: call signext i32 @memcmp
+define i32 @fun(i8* %0, i8* %1) {
+  %3 = call signext i32 @memcmp(i8* %0, i8* %1, i64 2)
+  %4 = icmp eq i32 %3, 0
+  %5 = zext i1 %4 to i32
+  ret i32 %5
+}
+
+declare dso_local signext i32 @memcmp(i8*, i8*, i64)