[PATCH] D54129: [AArch64] [Windows] Trap after noreturn calls.

[Eli Friedman via Phabricator via llvm-commits]

efriedma created this revision.
efriedma added a reviewer: rnk.
Herald added subscribers: kristof.beyls, javed.absar.

Like the comment says, this isn't the most efficient fix in terms of codesize, but it works.


Repository:
  rL LLVM

https://reviews.llvm.org/D54129

Files:
  lib/Target/AArch64/AArch64TargetMachine.cpp
  test/CodeGen/AArch64/windows-trap.ll


Index: test/CodeGen/AArch64/windows-trap.ll
===================================================================
--- /dev/null
+++ test/CodeGen/AArch64/windows-trap.ll
@@ -0,0 +1,17 @@
+; RUN: llc -mtriple=aarch64-win32 %s -o - | FileCheck %s
+
+declare void @callee() noreturn
+
+; Make sure the call isn't the last instruction in the function; if it is,
+; unwinding may break.
+;
+; (The instruction after the call doesn't have to be anything in particular,
+; but trapping has the nice side-effect of catching bugs.)
+
+define void @test_unreachable() {
+; CHECK-LABEL: test_unreachable:
+; CHECK: bl      callee
+; CHECK-NEXT: brk #0x1
+  call void @callee() noreturn
+  unreachable
+}
Index: lib/Target/AArch64/AArch64TargetMachine.cpp
===================================================================
--- lib/Target/AArch64/AArch64TargetMachine.cpp
+++ lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -263,6 +263,15 @@
     this->Options.NoTrapAfterNoreturn = true;
   }
 
+  if (TT.isOSWindows()) {
+    // Unwinding can get confused if the last instruction in a function or
+    // funclet is a call.
+    //
+    // FIXME: This isn't very efficient; it's only really necessary if the
+    // call would be the last instruction in a function/funclet.
+    this->Options.TrapUnreachable = true;
+  }
+
   // Enable GlobalISel at or below EnableGlobalISelAt0.
   if (getOptLevel() <= EnableGlobalISelAtO)
     setGlobalISel(true);


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