[llvm] [BOLT] Support map other function entry address (PR #101466)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-bolt

Author: sinan (linsinan1995)

<details>
<summary>Changes</summary>

Allow BOLT to map the old address to a new binary address if the old address is the entry of the function.

---
Full diff: https://github.com/llvm/llvm-project/pull/101466.diff


2 Files Affected:

- (modified) bolt/lib/Rewrite/RewriteInstance.cpp (+8) 
- (added) bolt/test/X86/dynamic-relocs-on-entry.s (+25) 


``````````diff
diff --git a/bolt/lib/Rewrite/RewriteInstance.cpp b/bolt/lib/Rewrite/RewriteInstance.cpp
index 9077869fe4955..e2273472c15de 100644
--- a/bolt/lib/Rewrite/RewriteInstance.cpp
+++ b/bolt/lib/Rewrite/RewriteInstance.cpp
@@ -5509,6 +5509,14 @@ uint64_t RewriteInstance::getNewFunctionOrDataAddress(uint64_t OldAddress) {
   if (const BinaryFunction *BF =
           BC->getBinaryFunctionContainingAddress(OldAddress)) {
     if (BF->isEmitted()) {
+      // If OldAddress is the another entry point of
+      // the function, then BOLT could get the new address.
+      if (BF->isMultiEntry()) {
+        for (auto &BB : *BF)
+          if (BB.isEntryPoint() &&
+              (BF->getAddress() + BB.getOffset()) == OldAddress)
+            return BF->getOutputAddress() + BB.getOffset();
+      }
       BC->errs() << "BOLT-ERROR: unable to get new address corresponding to "
                     "input address 0x"
                  << Twine::utohexstr(OldAddress) << " in function " << *BF
diff --git a/bolt/test/X86/dynamic-relocs-on-entry.s b/bolt/test/X86/dynamic-relocs-on-entry.s
new file mode 100644
index 0000000000000..7f47955440dd4
--- /dev/null
+++ b/bolt/test/X86/dynamic-relocs-on-entry.s
@@ -0,0 +1,25 @@
+// This test examines whether BOLT can correctly update when
+// dynamic relocation points to other entry points of the
+// function.
+
+# RUN: %clang %cflags -fPIC -pie %s -o %t.exe -nostdlib -Wl,-q
+# RUN: llvm-bolt %t.exe -o %t.bolt | FileCheck %s
+
+    .text
+    .type   chain, @function
+chain:
+    movq    $1, %rax
+Lable:
+    ret
+    .size   chain, .-chain
+    .type   _start, @function
+    .global _start
+_start:
+    jmpq    *.Lfoo(%rip)
+    ret
+    .size   _start, .-_start
+  .data
+.Lfoo:
+  .quad Lable
+
+# CHECK-NOT: BOLT-ERROR

``````````

</details>


https://github.com/llvm/llvm-project/pull/101466