Fix VSO 462269.

When decomposing a long compare on 32-bit platforms, the operands to the
decomposed compare must be sign- or zero-extended appropriately.

2 files changed, 43 insertions, 2 deletions

diff --git a/src/jit/decomposelongs.cpp b/src/jit/decomposelongs.cpp
index 96d3b0bb71..7cf1049ef4 100644
--- a/src/jit/decomposelongs.cpp
+++ b/src/jit/decomposelongs.cpp
@@ -607,7 +607,8 @@ GenTree* DecomposeLongs::DecomposeCast(LIR::Use& use)
             // check provided by codegen.
             //
 
-            loResult = loSrcOp;
+            const bool signExtend = (cast->gtFlags & GTF_UNSIGNED) == 0;
+            loResult              = EnsureIntSized(loSrcOp, signExtend);
 
             hiResult                       = cast;
             hiResult->gtType               = TYP_INT;
@@ -657,7 +658,9 @@ GenTree* DecomposeLongs::DecomposeCast(LIR::Use& use)
             }
             else if (varTypeIsUnsigned(srcType))
             {
-                loResult = cast->gtGetOp1();
+                const bool signExtend = (cast->gtFlags & GTF_UNSIGNED) == 0;
+                loResult              = EnsureIntSized(cast->gtGetOp1(), signExtend);
+
                 hiResult = m_compiler->gtNewZeroConNode(TYP_INT);
 
                 Range().InsertAfter(cast, hiResult);
@@ -1918,6 +1921,43 @@ GenTree* DecomposeLongs::RepresentOpAsLocalVar(GenTree* op, GenTree* user, GenTr
 }
 
 //------------------------------------------------------------------------
+// DecomposeLongs::EnsureIntSized:
+//    Checks to see if the given node produces an int-sized value and
+//    performs the appropriate widening if it does not.
+//
+// Arguments:
+//    node       - The node that may need to be widened.
+//    signExtend - True if the value should be sign-extended; false if it
+//                 should be zero-extended.
+//
+// Return Value:
+//    The node that produces the widened value.
+GenTree* DecomposeLongs::EnsureIntSized(GenTree* node, bool signExtend)
+{
+    assert(node != nullptr);
+    if (!varTypeIsSmall(node))
+    {
+        assert(genTypeSize(node) == genTypeSize(TYP_INT));
+        return node;
+    }
+
+    if (node->OperIs(GT_LCL_VAR) && !m_compiler->lvaTable[node->AsLclVarCommon()->gtLclNum].lvNormalizeOnLoad())
+    {
+        node->gtType = TYP_INT;
+        return node;
+    }
+
+    GenTree* const cast = m_compiler->gtNewCastNode(TYP_INT, node, node->TypeGet());
+    if (!signExtend)
+    {
+        cast->gtFlags |= GTF_UNSIGNED;
+    }
+
+    Range().InsertAfter(node, cast);
+    return cast;
+}
+
+//------------------------------------------------------------------------
 // GetHiOper: Convert arithmetic operator to "high half" operator of decomposed node.
 //
 // Arguments:
diff --git a/src/jit/decomposelongs.h b/src/jit/decomposelongs.h
index ff4f4ac880..7a0d6ff5ba 100644
--- a/src/jit/decomposelongs.h
+++ b/src/jit/decomposelongs.h
@@ -61,6 +61,7 @@ private:
     // Helper functions
     GenTree* FinalizeDecomposition(LIR::Use& use, GenTree* loResult, GenTree* hiResult, GenTree* insertResultAfter);
     GenTree* RepresentOpAsLocalVar(GenTree* op, GenTree* user, GenTree** edge);
+    GenTree* EnsureIntSized(GenTree* node, bool signExtend);
 
     GenTree* StoreNodeToVar(LIR::Use& use);
     static genTreeOps GetHiOper(genTreeOps oper);