[lld] r359094 - [PPC64] Consider localentry offset when computing branch distance

[Fangrui Song via llvm-commits]

Author: maskray
Date: Wed Apr 24 07:03:30 2019
New Revision: 359094

URL: http://llvm.org/viewvc/llvm-project?rev=359094&view=rev
Log:
[PPC64] Consider localentry offset when computing branch distance

Summary:
We don't take localentry offset into account, and thus may fail to
create a long branch when the gap is just a few bytes smaller than 2^25.

relocation R_PPC64_REL24 out of range: 33554432 is not in [-33554432, 33554431]
relocation R_PPC64_REL24 out of range: 33554436 is not in [-33554432, 33554431]

Fix that by adding the offset to the symbol VA.

Differential Revision: https://reviews.llvm.org/D61058

Added:
    lld/trunk/test/ELF/ppc64-long-branch-localentry-offset.s
Modified:
    lld/trunk/ELF/Arch/PPC64.cpp

Modified: lld/trunk/ELF/Arch/PPC64.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Arch/PPC64.cpp?rev=359094&r1=359093&r2=359094&view=diff
==============================================================================
--- lld/trunk/ELF/Arch/PPC64.cpp (original)
+++ lld/trunk/ELF/Arch/PPC64.cpp Wed Apr 24 07:03:30 2019
@@ -774,7 +774,10 @@ bool PPC64::needsThunk(RelExpr Expr, Rel
 
   // If the offset exceeds the range of the branch type then it will need
   // a range-extending thunk.
-  return !inBranchRange(Type, BranchAddr, S.getVA());
+  // See the comment in getRelocTargetVA() about R_PPC64_CALL.
+  return !inBranchRange(Type, BranchAddr,
+                        S.getVA() +
+                            getPPC64GlobalEntryToLocalEntryOffset(S.StOther));
 }
 
 bool PPC64::inBranchRange(RelType Type, uint64_t Src, uint64_t Dst) const {

Added: lld/trunk/test/ELF/ppc64-long-branch-localentry-offset.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/ppc64-long-branch-localentry-offset.s?rev=359094&view=auto
==============================================================================
--- lld/trunk/test/ELF/ppc64-long-branch-localentry-offset.s (added)
+++ lld/trunk/test/ELF/ppc64-long-branch-localentry-offset.s Wed Apr 24 07:03:30 2019
@@ -0,0 +1,30 @@
+# REQUIRES: ppc
+
+# RUN: llvm-mc -filetype=obj -triple=ppc64le %s -o %t.o
+# RUN: ld.lld %t.o -o %t
+# RUN: llvm-nm %t | FileCheck %s
+
+# CHECK-DAG: 0000000010010000 t __long_branch_callee
+# CHECK-DAG: 0000000010010010 T _start
+# CHECK-DAG: 0000000012010008 T callee
+
+# The bl instruction jumps to the local entry. The distance requires a long branch stub:
+# localentry(callee) - _start = 0x12010008+8 - 0x10010010 = 0x2000000
+
+# We used to compute globalentry(callee) - _start and caused a "R_PPC64_REL24
+# out of range" error because we didn't create the stub.
+
+.globl _start
+_start:
+  bl callee
+
+.space 0x1fffff4
+
+.globl callee
+callee:
+.Lgep0:
+  addis 2, 12, .TOC.-.Lgep0 at ha
+  addi 2, 2, .TOC.-.Lgep0 at l
+.Llep0:
+  .localentry callee, .Llep0-.Lgep0
+  blr