[PATCH] D104807: [SjLj] Insert UnregisterFn before musttail call

[Xun Li via Phabricator via llvm-commits]

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When inserting UnregisterFn, if there is a musttail call, we must insert before the call so that we don't break the musttail call contract.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D104807

Files:
  llvm/lib/CodeGen/SjLjEHPrepare.cpp
  llvm/test/CodeGen/X86/sjlj-eh-musttail.ll


Index: llvm/test/CodeGen/X86/sjlj-eh-musttail.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/sjlj-eh-musttail.ll
@@ -0,0 +1,30 @@
+; RUN: llc -mtriple i386-windows-gnu -exception-model sjlj -filetype asm -o - %s | FileCheck %s
+
+declare void @_Z20function_that_throwsv()
+declare i32 @__gxx_personality_sj0(...)
+declare i8* @__cxa_begin_catch(i8*)
+declare void @__cxa_end_catch()
+declare void @_callee();
+
+define void @_Z8functionv() personality i8* bitcast (i32 (...)* @__gxx_personality_sj0 to i8*) {
+entry:
+  invoke void @_Z20function_that_throwsv()
+          to label %try.cont unwind label %lpad
+
+lpad:
+  %0 = landingpad { i8*, i32 }
+          catch i8* null
+  %1 = extractvalue { i8*, i32 } %0, 0
+  %2 = tail call i8* @__cxa_begin_catch(i8* %1)
+  tail call void @__cxa_end_catch()
+  br label %try.cont
+
+try.cont:
+  musttail call void @_callee();
+  ret void
+}
+
+; CHECK-LABEL: __Z8functionv:
+; CHECK:         calll   __Unwind_SjLj_Unregister
+; CHECK-NOT:     {{.*}}:
+; CHECK:         jmp     __callee
Index: llvm/lib/CodeGen/SjLjEHPrepare.cpp
===================================================================
--- llvm/lib/CodeGen/SjLjEHPrepare.cpp
+++ llvm/lib/CodeGen/SjLjEHPrepare.cpp
@@ -472,8 +472,12 @@
 
   // Finally, for any returns from this function, if this function contains an
   // invoke, add a call to unregister the function context.
-  for (ReturnInst *Return : Returns)
-    CallInst::Create(UnregisterFn, FuncCtx, "", Return);
+  for (ReturnInst *Return : Returns) {
+    Instruction *InsertPoint = Return;
+    if (CallInst *CI = Return->getParent()->getTerminatingMustTailCall())
+      InsertPoint = CI;
+    CallInst::Create(UnregisterFn, FuncCtx, "", InsertPoint);
+  }
 
   return true;
 }


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