[llvm] [BOLT][AArch64] Create entry points for addresses referenced by dynamic relocations and allow getNewFunctionOrDataAddress to map addrs inside functions. (PR #120267)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-bolt

Author: Rin Dobrescu (Rin18)

<details>
<summary>Changes</summary>

By adding addresses referenced by dynamic relocations as entry points, this patch fixes an issue where bolt fails on code using computing goto's. This also fixes a mapping issue with the bugfix from this PR: https://github.com/llvm/llvm-project/pull/117766.

---
Full diff: https://github.com/llvm/llvm-project/pull/120267.diff


2 Files Affected:

- (modified) bolt/lib/Rewrite/RewriteInstance.cpp (+9-1) 
- (added) bolt/test/AArch64/computed-goto.s (+39) 


``````````diff
diff --git a/bolt/lib/Rewrite/RewriteInstance.cpp b/bolt/lib/Rewrite/RewriteInstance.cpp
index 4329235d470497..55fcd6b6e782c4 100644
--- a/bolt/lib/Rewrite/RewriteInstance.cpp
+++ b/bolt/lib/Rewrite/RewriteInstance.cpp
@@ -2439,6 +2439,14 @@ void RewriteInstance::readDynamicRelocations(const SectionRef &Section,
     if (Symbol)
       SymbolIndex[Symbol] = getRelocationSymbol(InputFile, Rel);
 
+    const uint64_t SymAddress = SymbolAddress + Addend;
+    BinaryFunction *Func = BC->getBinaryFunctionContainingAddress(SymAddress);
+    if(Func){
+      const uint64_t FunctionOffset = SymAddress - Func->getAddress();
+      if(FunctionOffset)
+        Func->addEntryPointAtOffset(FunctionOffset);
+    }
+
     BC->addDynamicRelocation(Rel.getOffset(), Symbol, RType, Addend);
   }
 }
@@ -5599,7 +5607,7 @@ uint64_t RewriteInstance::getNewFunctionOrDataAddress(uint64_t OldAddress) {
         for (const BinaryBasicBlock &BB : *BF)
           if (BB.isEntryPoint() &&
               (BF->getAddress() + BB.getOffset()) == OldAddress)
-            return BF->getOutputAddress() + BB.getOffset();
+            return BB.getOutputStartAddress();
       }
       BC->errs() << "BOLT-ERROR: unable to get new address corresponding to "
                     "input address 0x"
diff --git a/bolt/test/AArch64/computed-goto.s b/bolt/test/AArch64/computed-goto.s
new file mode 100644
index 00000000000000..043f9a8e37e6b0
--- /dev/null
+++ b/bolt/test/AArch64/computed-goto.s
@@ -0,0 +1,39 @@
+# RUN: llvm-mc -filetype=obj -triple aarch64-unknown-unknown %s -o %t.o
+# RUN: %clang %cflags %t.o -o %t.exe -Wl,-q
+# RUN: llvm-bolt %t.exe -o %t.bolt 2>&1 | FileCheck %s
+
+## Before bolt could handle mapping addresses within moved functions, it
+## would bail out with an error of the form:
+## BOLT-ERROR: unable to get new address corresponding to input address 0x10390 in function main. Consider adding this function to --skip-funcs=...
+## These addresses arise if computed GOTO is in use.
+## Check that bolt does not emit any error.
+
+# CHECK-NOT: BOLT-ERROR
+
+.globl  main
+.p2align        2
+.type   main, at function
+main:
+.cfi_startproc
+        adrp    x8, .L__const.main.ptrs+8
+        add     x8, x8, :lo12:.L__const.main.ptrs+8
+        ldr     x9, [x8], #8
+        br      x9
+
+.Label0: // Block address taken
+        ldr     x9, [x8], #8
+        br      x9
+
+.Label1: // Block address taken
+        mov     w0, #42
+        ret
+
+.Lfunc_end0:
+.size   main, .Lfunc_end0-main
+.cfi_endproc
+        .type   .L__const.main.ptrs, at object
+        .section        .data.rel.ro,"aw", at progbits
+        .p2align        3, 0x0
+.L__const.main.ptrs:
+        .xword  .Label0
+        .xword  .Label1

``````````

</details>


https://github.com/llvm/llvm-project/pull/120267