[PATCH] D159513: [Bolt] fix a relocation bug for R_AARCH64_CALL26

[Sinan Lin via Phabricator via llvm-commits]

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If the R_AARCH64_CALL26 against a symbol that has a lower address, then `encodeValueAArch64` will return a wrong value.

In the included test case, the expected output of `encodeValueAArch64` is 97ffffff, but it returns `3fffffffffffffff`, and then an invalid instruction is encoded.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159513

Files:
  bolt/lib/Core/Relocation.cpp
  bolt/test/AArch64/reloc-call26-overflow.s


Index: bolt/test/AArch64/reloc-call26-overflow.s
===================================================================
--- /dev/null
+++ bolt/test/AArch64/reloc-call26-overflow.s
@@ -0,0 +1,25 @@
+# REQUIRES: system-linux
+
+# RUN: llvm-mc -filetype=obj -triple aarch64-unknown-unknown \
+# RUN:   %s -o %t.o
+# RUN: %clang %cflags %t.o -o %t.exe -Wl,-q
+# RUN: llvm-bolt %t.exe -o %t.bolt --funcs=func1 --force-patch
+# RUN: llvm-objdump -d --disassemble-symbols='_start' %t.bolt | \
+# RUN:   FileCheck %s
+
+# CHECK: {{.*}} bl {{.*}} <func1>
+
+  .text
+  .align 4
+  .global func1
+  .type func1, %function
+func1:
+  ret
+  .size func1, .-func1
+  .global _start
+  .type _start, %function
+_start:
+  bl func1
+  mov     w8, #93
+  svc     #0
+  .size _start, .-_start
Index: bolt/lib/Core/Relocation.cpp
===================================================================
--- bolt/lib/Core/Relocation.cpp
+++ bolt/lib/Core/Relocation.cpp
@@ -352,7 +352,7 @@
     assert(isInt<28>(Value) && "only PC +/- 128MB is allowed for direct call");
     // Immediate goes in bits 25:0 of BL.
     // OP 1001_01 goes in bits 31:26 of BL.
-    Value = (Value >> 2) | 0x94000000ULL;
+    Value = ((Value >> 2) & 0x3ffffff) | 0x94000000ULL;
     break;
   }
   return Value;


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