[llvm] e16ec9b - [SelectionDAG] Do not build illegal nodes with users (#108573)

[via llvm-commits]

Author: ErikHogeman
Date: 2024-09-16T10:02:42+01:00
New Revision: e16ec9b45e4a8fd3fdc67338ea9c77457460a25a

URL: https://github.com/llvm/llvm-project/commit/e16ec9b45e4a8fd3fdc67338ea9c77457460a25a
DIFF: https://github.com/llvm/llvm-project/commit/e16ec9b45e4a8fd3fdc67338ea9c77457460a25a.diff

LOG: [SelectionDAG] Do not build illegal nodes with users (#108573)

When we build a node with illegal type which has a user, it's possible
that it can end up being processed by the DAG combiner later before it's
removed, which can trigger an assert expecting the types to be legalized
already.

Added: 
    

Modified: 
    llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 29505f444b7650..44ec6f7cab145a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -6799,14 +6799,17 @@ SDValue SelectionDAG::FoldConstantArithmetic(unsigned Opcode, const SDLoc &DL,
     // Constant fold the scalar operands.
     SDValue ScalarResult = getNode(Opcode, DL, SVT, ScalarOps, Flags);
 
-    // Legalize the (integer) scalar constant if necessary.
-    if (LegalSVT != SVT)
-      ScalarResult = getNode(ExtendCode, DL, LegalSVT, ScalarResult);
-
     // Scalar folding only succeeded if the result is a constant or UNDEF.
     if (!ScalarResult.isUndef() && ScalarResult.getOpcode() != ISD::Constant &&
         ScalarResult.getOpcode() != ISD::ConstantFP)
       return SDValue();
+
+    // Legalize the (integer) scalar constant if necessary. We only do
+    // this once we know the folding succeeded, since otherwise we would
+    // get a node with illegal type which has a user.
+    if (LegalSVT != SVT)
+      ScalarResult = getNode(ExtendCode, DL, LegalSVT, ScalarResult);
+
     ScalarResults.push_back(ScalarResult);
   }