[llvm-branch-commits] [lld] ELF: CFI jump table relaxation. (PR #147424)

[Fangrui Song via llvm-branch-commits]

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@@ -312,6 +313,196 @@ bool X86_64::deleteFallThruJmpInsn(InputSection &is,
   return true;
 }
 
+void X86_64::relaxCFIJumpTables() const {
+  // Relax CFI jump tables.
+  // - Split jump table into pieces and place target functions inside the jump
+  //   table if small enough.
+  // - Move jump table before last called function and delete last branch
+  //   instruction.
+  DenseMap<InputSection *, SmallVector<InputSection *, 0>> sectionReplacements;
+  SmallVector<InputSection *, 0> storage;
+  for (OutputSection *osec : ctx.outputSections) {
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MaskRay wrote:

This slow input section iteration causes unneeded overhead for the majority of use cases that don't use  cfi jump table.

https://github.com/llvm/llvm-project/pull/147424