[PATCH] D109248: Annotate `llvm.eh.sjlj.setjmp` as `returns_twice`

[Tee KOBAYASHI via Phabricator via llvm-commits]

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In LLVM, some optimizations are disabled for functions that return twice. For instance, register coalescing in those functions is disabled by D77767 <https://reviews.llvm.org/D77767>. Currently, this does not apply to `__builtin_setjmp`, because the intrinsic function `llvm.eh.sjlj.setjmp` is not annotated as `returns_twice`.

In the proposed change, we annotate `llvm.eh.sjlj.setjmp` as `returns_twice`. This fixes PR50234.


https://reviews.llvm.org/D109248

Files:
  llvm/include/llvm/IR/Intrinsics.td
  llvm/utils/TableGen/CodeGenIntrinsics.h
  llvm/utils/TableGen/CodeGenTarget.cpp
  llvm/utils/TableGen/IntrinsicEmitter.cpp


Index: llvm/utils/TableGen/IntrinsicEmitter.cpp
===================================================================
--- llvm/utils/TableGen/IntrinsicEmitter.cpp
+++ llvm/utils/TableGen/IntrinsicEmitter.cpp
@@ -590,6 +590,9 @@
     if (L->isNoReturn != R->isNoReturn)
       return R->isNoReturn;
 
+    if (L->isReturnsTwice != R->isReturnsTwice)
+      return R->isReturnsTwice;
+
     if (L->isNoSync != R->isNoSync)
       return R->isNoSync;
 
@@ -739,7 +742,8 @@
     if (!Intrinsic.canThrow ||
         (Intrinsic.ModRef != CodeGenIntrinsic::ReadWriteMem &&
          !Intrinsic.hasSideEffects) ||
-        Intrinsic.isNoReturn || Intrinsic.isNoSync || Intrinsic.isNoFree ||
+        Intrinsic.isNoReturn || Intrinsic.isReturnsTwice ||
+        Intrinsic.isNoSync || Intrinsic.isNoFree ||
         Intrinsic.isWillReturn || Intrinsic.isCold || Intrinsic.isNoDuplicate ||
         Intrinsic.isNoMerge || Intrinsic.isConvergent ||
         Intrinsic.isSpeculatable) {
@@ -749,6 +753,8 @@
         OS << LS << "Attribute::NoUnwind";
       if (Intrinsic.isNoReturn)
         OS << LS << "Attribute::NoReturn";
+      if (Intrinsic.isReturnsTwice)
+        OS << LS << "Attribute::ReturnsTwice";
       if (Intrinsic.isNoSync)
         OS << LS << "Attribute::NoSync";
       if (Intrinsic.isNoFree)
Index: llvm/utils/TableGen/CodeGenTarget.cpp
===================================================================
--- llvm/utils/TableGen/CodeGenTarget.cpp
+++ llvm/utils/TableGen/CodeGenTarget.cpp
@@ -666,6 +666,7 @@
   isCommutative = false;
   canThrow = false;
   isNoReturn = false;
+  isReturnsTwice = false;
   isNoSync = false;
   isNoFree = false;
   isWillReturn = false;
@@ -867,6 +868,8 @@
     isConvergent = true;
   else if (R->getName() == "IntrNoReturn")
     isNoReturn = true;
+  else if (R->getName() == "IntrReturnsTwice")
+    isReturnsTwice = true;
   else if (R->getName() == "IntrNoSync")
     isNoSync = true;
   else if (R->getName() == "IntrNoFree")
Index: llvm/utils/TableGen/CodeGenIntrinsics.h
===================================================================
--- llvm/utils/TableGen/CodeGenIntrinsics.h
+++ llvm/utils/TableGen/CodeGenIntrinsics.h
@@ -126,6 +126,9 @@
   /// True if the intrinsic is no-return.
   bool isNoReturn;
 
+  /// True if the intrinsic is returns-twice.
+  bool isReturnsTwice;
+
   /// True if the intrinsic is no-sync.
   bool isNoSync;
 
Index: llvm/include/llvm/IR/Intrinsics.td
===================================================================
--- llvm/include/llvm/IR/Intrinsics.td
+++ llvm/include/llvm/IR/Intrinsics.td
@@ -120,6 +120,8 @@
 
 def IntrNoReturn : IntrinsicProperty;
 
+def IntrReturnsTwice : IntrinsicProperty;
+
 // IntrNoSync - Threads executing the intrinsic will not synchronize using
 // memory or other means. Applied by default.
 def IntrNoSync : IntrinsicProperty<1>;
@@ -984,7 +986,8 @@
 def int_eh_sjlj_callsite         : Intrinsic<[], [llvm_i32_ty], [IntrNoMem]>;
 
 def int_eh_sjlj_functioncontext : Intrinsic<[], [llvm_ptr_ty]>;
-def int_eh_sjlj_setjmp          : Intrinsic<[llvm_i32_ty], [llvm_ptr_ty]>;
+def int_eh_sjlj_setjmp          : Intrinsic<[llvm_i32_ty], [llvm_ptr_ty],
+                                            [IntrReturnsTwice]>;
 def int_eh_sjlj_longjmp         : Intrinsic<[], [llvm_ptr_ty], [IntrNoReturn]>;
 def int_eh_sjlj_setup_dispatch  : Intrinsic<[], []>;
 


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