[PATCH] D87506: [SystemZ] Make LibFunc_bcmp unavailable

[Jonas Paulsson via Phabricator via llvm-commits]

jonpa created this revision.
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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.


https://reviews.llvm.org/D87506

Files:
  llvm/lib/Analysis/TargetLibraryInfo.cpp
  llvm/test/Transforms/InstCombine/memcmp-3.ll


Index: llvm/test/Transforms/InstCombine/memcmp-3.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/memcmp-3.ll
@@ -0,0 +1,18 @@
+; 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)
Index: llvm/lib/Analysis/TargetLibraryInfo.cpp
===================================================================
--- llvm/lib/Analysis/TargetLibraryInfo.cpp
+++ llvm/lib/Analysis/TargetLibraryInfo.cpp
@@ -143,7 +143,8 @@
     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 &&


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