Merge remote-tracking branch 'origin/main' into pauthlr-prologue

Author: ostannard

bolt/lib/Core/BinaryFunction.cpp

@@ -795,7 +795,6 @@ BinaryFunction::processIndirectBranch(MCInst &Instruction, unsigned Size,
 
   auto Begin = Instructions.begin();
   if (BC.isAArch64()) {
-    PreserveNops = BC.HasRelocations;
     // Start at the last label as an approximation of the current basic block.
     // This is a heuristic, since the full set of labels have yet to be
     // determined
@@ -2300,6 +2299,10 @@ Error BinaryFunction::buildCFG(MCPlusBuilder::AllocatorIdTy AllocatorId) {
       BC.errs() << "BOLT-WARNING: failed to post-process indirect branches for "
                 << *this << '\n';
     }
+
+    if (BC.isAArch64())
+      PreserveNops = BC.HasRelocations;
+
     // In relocation mode we want to keep processing the function but avoid
     // optimizing it.
     setSimple(false);

bolt/test/AArch64/remove-nops.s

@@ -0,0 +1,28 @@
+## Verify that llvm-bolt removes nop instructions from functions with indirect
+## branches that have defined control flow.
+
+# REQUIRES: system-linux
+
+# RUN: llvm-mc -filetype=obj -triple aarch64-unknown-unknown %s -o %t.o
+# RUN: %clang %cflags --target=aarch64-unknown-linux %t.o -o %t.exe -Wl,-q
+# RUN: llvm-bolt %t.exe -o %t.bolt --print-normalized 2>&1 | FileCheck %s
+# RUN: llvm-objdump -d --disassemble-symbols=_start %t.bolt \
+# RUN:   | FileCheck %s --check-prefix=CHECK-OBJDUMP
+
+# CHECK-OBJDUMP-LABEL: _start
+# CHECK-OBJDUMP-NOT: nop
+
+  .section .text
+  .align 4
+  .globl _start
+  .type  _start, %function
+_start:
+# CHECK-LABEL: Binary Function "_start"
+  nop
+# CHECK-NOT: nop
+  br      x0
+# CHECK: br x0 # TAILCALL
+.size _start, .-_start
+
+## Force relocation mode.
+  .reloc 0, R_AARCH64_NONE