JIT: fix issue with partial comp pred list maintenance

AndyAyersMS · AndyAyersMS · commit bd42165e68fd · 2023-02-03T10:09:49.000-08:00
We may have degenerate flow out of a partial compilation block, so make sure to fully remove the block from all successor pred lists. Fixes issue seen in dotnet#80635.
diff --git a/src/coreclr/jit/importer.cpp b/src/coreclr/jit/importer.cpp
@@ -6369,7 +6369,8 @@ void Compiler::impImportBlockCode(BasicBlock* block)
             //
             for (BasicBlock* const succ : block->Succs())
             {
-                fgRemoveRefPred(succ, block);
+                // We may have degenerate flow, make sure to fully remove
+                fgRemoveAllRefPreds(succ, block);
             }
 
             // Change block to BBJ_THROW so we won't trigger importation of successors.

Original file line number	Diff line number	Diff line change
`@@ -6369,7 +6369,8 @@ void Compiler::impImportBlockCode(BasicBlock* block)`
`6369`	`6369`	`//`
`6370`	`6370`	`for (BasicBlock* const succ : block->Succs())`
`6371`	`6371`	`{`
`6372`		`- fgRemoveRefPred(succ, block);`
	`6372`	`+ // We may have degenerate flow, make sure to fully remove`
	`6373`	`+ fgRemoveAllRefPreds(succ, block);`
`6373`	`6374`	`}`
`6374`	`6375`
`6375`	`6376`	`// Change block to BBJ_THROW so we won't trigger importation of successors.`