[llvm] [AArch64][BTI] Add BTI at EH entries. (PR #155308)

[David Green via llvm-commits]

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@@ -0,0 +1,45 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=aarch64-unknown-linux-gnu %s -o - | FileCheck %s
+
+declare i32 @__gxx_personality_v0(...)
+declare void @may_throw()
+
+define void @test() #0 personality ptr @__gxx_personality_v0 {
+; CHECK-LABEL: {{^test:.*$}}
+; CHECK:       .Lfunc_begin0:
+; CHECK-NEXT:    .cfi_startproc
+; CHECK-NEXT:    .cfi_personality 156, DW.ref.__gxx_personality_v0
+; CHECK-NEXT:    .cfi_lsda 28, .Lexception0
+; CHECK-NEXT:  // %bb.0: // %entry
+; CHECK-NEXT:    bti c
+; CHECK-NEXT:    str x30, [sp, #-16]! // 8-byte Folded Spill
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    .cfi_offset w30, -16
+; CHECK-NEXT:  .Ltmp0: // EH_LABEL
+; CHECK-NEXT:    bl may_throw
+; CHECK-NEXT:  .Ltmp1: // EH_LABEL
+; CHECK-NEXT:  // %bb.1: // %common.ret
+; CHECK-NEXT:    ldr x30, [sp], #16 // 8-byte Folded Reload
+; CHECK-NEXT:    ret
+; CHECK-NEXT:  .LBB0_2: // %lpad
+; CHECK-NEXT:  .Ltmp2: // EH_LABEL
+; CHECK-NEXT:    bti j
+; CHECK-NEXT:    ldr x30, [sp], #16 // 8-byte Folded Reload
+; CHECK-NEXT:    ret
+entry:
+  invoke void @may_throw()
+          to label %ret unwind label %lpad
+
+lpad:
+  landingpad { ptr, i32 } cleanup
+  ret void
+
+ret:
+  ret void
+}
+
+; Enforce BTI at codegen.
+attributes #0 = { noinline "branch-target-enforcement"="true" "target-features"="+bti" }
+
+; (No extra BTI checks needed—the autogenerated CHECK block above already
+;  asserts that the landing pad label is followed by EH_LABEL and `bti j`.)
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davemgreen wrote:

Maybe move this up or reword it to above the function definition, to explain that the bti j should be below the EH_LABEL in the lpad block.

https://github.com/llvm/llvm-project/pull/155308