From 307e20200c2f965401968fe2f38ababffd4197af Mon Sep 17 00:00:00 2001
From: Andy Ayers <andya@microsoft.com>
Date: Mon, 4 Aug 2025 17:50:09 -0700
Subject: [PATCH] JIT: postorder local assertion prop for fieldwise block op
 indirs

After we form the block op field indirs, run postorder local assertion
prop on them, so that they see the same amount of assertion prop as
other indirs.

Fixes (parts of) #115789.
---
 src/coreclr/jit/morphblock.cpp | 39 +++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/src/coreclr/jit/morphblock.cpp b/src/coreclr/jit/morphblock.cpp
index ac234686a63614..452983ffc50597 100644
--- a/src/coreclr/jit/morphblock.cpp
+++ b/src/coreclr/jit/morphblock.cpp
@@ -1164,6 +1164,32 @@ GenTree* MorphCopyBlockHelper::CopyFieldByField()
         addrSpillStore->SetMorphed(m_comp);
     }
 
+    auto postOrderAssertionProp = [=](GenTree* tree) {
+        if (m_comp->fgGlobalMorph && m_comp->optLocalAssertionProp && (m_comp->optAssertionCount > 0))
+        {
+            GenTree* optimizedTree = tree;
+            bool     again         = JitConfig.JitEnablePostorderLocalAssertionProp() > 0;
+            bool     didOptimize   = false;
+
+            while (again)
+            {
+                tree          = optimizedTree;
+                optimizedTree = m_comp->optAssertionProp(m_comp->apLocalPostorder, tree, nullptr, nullptr);
+                again         = (optimizedTree != nullptr);
+                didOptimize |= again;
+            }
+
+            assert(tree != nullptr);
+
+            if (didOptimize)
+            {
+                m_comp->gtUpdateNodeSideEffects(tree);
+            }
+        }
+
+        return tree;
+    };
+
     auto grabAddr = [=, &result](unsigned offs) {
         GenTree* addrClone = nullptr;
         // Need address of the source.
@@ -1316,6 +1342,8 @@ GenTree* MorphCopyBlockHelper::CopyFieldByField()
             }
         }
         assert(srcFld != nullptr);
+
+        srcFld = postOrderAssertionProp(srcFld);
         srcFld->SetMorphed(m_comp);
 
         GenTree* dstFldStore;
@@ -1372,7 +1400,16 @@ GenTree* MorphCopyBlockHelper::CopyFieldByField()
                 }
             }
         }
-        noway_assert(dstFldStore->TypeGet() == srcFld->TypeGet());
+
+        // Allow mismatched types only when srcFld is an integer constant
+        //
+        if (dstFldStore->TypeGet() != srcFld->TypeGet())
+        {
+            noway_assert(genActualType(dstFldStore->TypeGet()) == genActualType(srcFld->TypeGet()));
+            assert(srcFld->IsIntegralConst());
+        }
+
+        dstFldStore = postOrderAssertionProp(dstFldStore);
         dstFldStore->SetMorphed(m_comp);
 
         if (m_comp->optLocalAssertionProp)