[llvm] [CodeGen][SDAG] Track returntwice in lowering info (PR #92640)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-selectiondag

Author: None (aengelke)

<details>
<summary>Changes</summary>

This saves an extra iteration over the all instructions of the function.

---
Full diff: https://github.com/llvm/llvm-project/pull/92640.diff


2 Files Affected:

- (modified) llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp (+4) 
- (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp (-3) 


``````````diff
diff --git a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index 8fb6b11b8805c..6ea17b4386cda 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -214,6 +214,10 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
           if (CI->isMustTailCall() && Fn->isVarArg())
             MF->getFrameInfo().setHasMustTailInVarArgFunc(true);
         }
+
+        // Determine if there is a call to setjmp in the machine function.
+        if (Call->hasFnAttr(Attribute::ReturnsTwice))
+          MF->setExposesReturnsTwice(true);
       }
 
       // Mark values used outside their block as exported, by allocating
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index b5694c955b8c8..8addaf1ae3e54 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -680,9 +680,6 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
     }
   }
 
-  // Determine if there is a call to setjmp in the machine function.
-  MF->setExposesReturnsTwice(Fn.callsFunctionThatReturnsTwice());
-
   // Determine if floating point is used for msvc
   computeUsesMSVCFloatingPoint(TM.getTargetTriple(), Fn, MF->getMMI());
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/92640