[llvm-branch-commits] [DO_NOT_MERGE][ELF] Add statistics for CFI jump table relaxation (PR #222530)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lld

Author: Vitaly Buka (vitalybuka)

<details>
<summary>Changes</summary>

Add NumCfiJumpTablesInlined and NumCfiJumpTablesAdjustedLast statistics
to track the number of CFI jump table functions inlined and last entries
adjusted during relaxation.


---
Full diff: https://github.com/llvm/llvm-project/pull/222530.diff


1 Files Affected:

- (modified) lld/ELF/Arch/X86_64.cpp (+10) 


``````````diff
diff --git a/lld/ELF/Arch/X86_64.cpp b/lld/ELF/Arch/X86_64.cpp
index f095f3622cb85..8b3b04b81c1b3 100644
--- a/lld/ELF/Arch/X86_64.cpp
+++ b/lld/ELF/Arch/X86_64.cpp
@@ -13,10 +13,18 @@
 #include "SyntheticSections.h"
 #include "Target.h"
 #include "TargetImpl.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/MathExtras.h"
 
+#define DEBUG_TYPE "lld"
+
+STATISTIC(NumCfiJumpTablesInlined,
+          "Number of CFI jump table functions inlined");
+STATISTIC(NumCfiJumpTablesAdjustedLast,
+          "Number of CFI jump table last entries adjusted");
+
 using namespace llvm;
 using namespace llvm::object;
 using namespace llvm::support::endian;
@@ -457,6 +465,7 @@ void X86_64::relaxCFIJumpTables() const {
               target && target->size != 0 && target->size <= sec->entsize &&
               target->addralign <= sec->entsize &&
               target->getParent() == targetOutputSec) {
+            ++NumCfiJumpTablesInlined;
             // Okay, we found a small enough section. Move it into the jump
             // table. First add a slice for the unmodified jump table entries
             // before this one. This slice may be of zero size if two
@@ -482,6 +491,7 @@ void X86_64::relaxCFIJumpTables() const {
       // function's body acts as the last jump table entry), otherwise leave the
       // jump table where it is and keep the last entry.
       if (lastSec) {
+        ++NumCfiJumpTablesAdjustedLast;
         addSectionSlice(begin, cur, rbegin, rcur);
         replacements.push_back(lastSec);
         sectionReplacements[sec] = {};

``````````

</details>


https://github.com/llvm/llvm-project/pull/222530