[PATCH] D26290: Only consider local functions local for the purpose of NOP eliminate after calls on PPC64

[Joerg Sonnenberger via llvm-commits]

joerg created this revision.
joerg added reviewers: wschmidt, hfinkel.
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Herald added a subscriber: nemanjai.

As shown in https://llvm.org/bugs/show_bug.cgi?id=30868 the current assumption  that ld will use local calls for global symbols is incorrect. For the nop elimination, we must use the much stricter ELF local symbol definition. At least GNU ld does assume that the call is otherwise interposable.


Repository:
  rL LLVM

https://reviews.llvm.org/D26290

Files:
  lib/Target/PowerPC/PPCISelLowering.cpp
  test/CodeGen/PowerPC/call-nop.ll


Index: test/CodeGen/PowerPC/call-nop.ll
===================================================================
--- test/CodeGen/PowerPC/call-nop.ll
+++ test/CodeGen/PowerPC/call-nop.ll
@@ -0,0 +1,27 @@
+; RUN: llc -O2 < %s | FileCheck %s
+
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc64--linux"
+
+ at f.x = internal global i32 0, align 4
+
+; Function Attrs: noinline nounwind
+define signext i32 @f() noinline {
+  %1 = load volatile i32, i32* @f.x, align 4
+  ret i32 %1
+}
+
+; Function Attrs: nounwind
+define signext i32 @g() {
+  %1 = call signext i32 @f()
+  %2 = call signext i32 @f()
+  %3 = add nsw i32 %1, %2
+  ret i32 %3
+}
+
+; CHECK-LABEL: @g
+; CHECK:      bl f
+; CHECK-NEXT: nop
+; CHECK:      bl f
+; CHECK-NEXT: nop
+
Index: lib/Target/PowerPC/PPCISelLowering.cpp
===================================================================
--- lib/Target/PowerPC/PPCISelLowering.cpp
+++ lib/Target/PowerPC/PPCISelLowering.cpp
@@ -4549,7 +4606,7 @@
 bool isLocalCall(const SDValue &Callee)
 {
   if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee))
-    return G->getGlobal()->isStrongDefinitionForLinker();
+    return G->getGlobal()->hasLocalLinkage();
   return false;
 }
 


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