[BOLT] Emit empty FDE for injected functions

This fixes an issue where `PatchEntries` overwrites function body but
keeps CFI untouched. Existing FDEs thus become invalid. This doesn't
affect unwinding because patched functions are transparent from
EH/unwinding perspective, but it breaks BOLT during disassembling those
functions.

Emit empty FDE for injected functions (emitted to the same address as
.org functions) that take precedence over the original FDE.

This adds eh_frame overhead, but restores the ability to disassemble
.org functions. Note that the overhead is avoided in `-use-old-text`
mode.

Test Plan: updated bolt/test/X86/patch-entries.test

Reviewers: rafaelauler, maksfb, dcci, ayermolo

Reviewed By: maksfb, dcci

Pull Request: #87967

Author: aaupov

bolt/include/bolt/Core/BinaryFunction.h

@@ -1402,7 +1402,8 @@ class BinaryFunction {
 
   /// Return true if the function has CFI instructions
   bool hasCFI() const {
-    return !FrameInstructions.empty() || !CIEFrameInstructions.empty();
+    return !FrameInstructions.empty() || !CIEFrameInstructions.empty() ||
+           IsInjected;
   }
 
   /// Return unique number associated with the function.

bolt/test/X86/patch-entries.test

@@ -7,4 +7,25 @@ REQUIRES: system-linux
 
 RUN: %clang %cflags -no-pie -g %p/Inputs/patch-entries.c -fuse-ld=lld -o %t.exe \
 RUN:   -Wl,-q -I%p/../Inputs
-RUN: llvm-bolt -relocs %t.exe -o %t.out --update-debug-sections --force-patch
+RUN: llvm-bolt -relocs %t.exe -o %t.out --update-debug-sections --force-patch \
+RUN:   --enable-bat
+
+# Check that patched functions can be disassembled (override FDE from the
+# original function)
+# PREAGG: B X:0 #foo.org.0# 1 0
+RUN: link_fdata %s %t.out %t.preagg PREAGG
+RUN: perf2bolt %t.out -p %t.preagg --pa -o %t.yaml --profile-format=yaml \
+RUN:   -print-disasm -print-only=foo.org.0/1 2>&1 | FileCheck %s
+CHECK-NOT: BOLT-WARNING: sizes differ for function foo.org.0/1
+CHECK: Binary Function "foo.org.0/1(*2)" after disassembly {
+
+# Check the expected eh_frame contents
+RUN: llvm-nm --print-size %t.out > %t.foo
+RUN: llvm-objdump %t.out --dwarf=frames >> %t.foo
+RUN: FileCheck %s --input-file %t.foo --check-prefix=CHECK-FOO
+CHECK-FOO: 0000000000[[#%x,FOO:]] [[#%x,OPTSIZE:]] t foo
+CHECK-FOO: 0000000000[[#%x,ORG:]] [[#%x,ORGSIZE:]] t foo.org.0
+# patched FDE comes first
+CHECK-FOO: FDE {{.*}} pc=00[[#%x,ORG]]...00[[#%x,ORG+ORGSIZE]]
+# original FDE comes second
+CHECK-FOO: FDE {{.*}} pc=00[[#%x,ORG]]...00[[#%x,ORG+OPTSIZE]]