Revert "JIT: Disallow implicit byref args and return buffers from ali…

…asing (dotnet#104616)" This reverts commit 6c55362.
matouskozak · Jul 11, 2024 · 6b4fb84 · 6b4fb84
1 parent 572014a
commit 6b4fb84
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Showing 3 changed files with 10 additions and 35 deletions.
diff --git a/src/coreclr/jit/gentree.cpp b/src/coreclr/jit/gentree.cpp
@@ -17974,14 +17974,11 @@ GenTreeLclVarCommon* GenTree::IsImplicitByrefParameterValuePreMorph(Compiler* co
 //    compiler - compiler instance
 //    addr     - [out] tree representing the address computation on top of the implicit byref.
 //               Will be the same as the return value if the whole implicit byref is used, for example.
-//    offset   - [out] Offset that "addr" is adding on top of the returned local.
 //
 // Return Value:
 //    Node for the local, or nullptr.
 //
-GenTreeLclVar* GenTree::IsImplicitByrefParameterValuePostMorph(Compiler*       compiler,
-                                                               GenTree**       addr,
-                                                               target_ssize_t* offset)
+GenTreeLclVar* GenTree::IsImplicitByrefParameterValuePostMorph(Compiler* compiler, GenTree** addr)
 {
 #if FEATURE_IMPLICIT_BYREFS && !defined(TARGET_LOONGARCH64) // TODO-LOONGARCH64-CQ: enable this.
 
@@ -17990,10 +17987,13 @@ GenTreeLclVar* GenTree::IsImplicitByrefParameterValuePostMorph(Compiler*       c
         return nullptr;
     }
 
-    *addr = AsIndir()->Addr();
-
+    *addr              = AsIndir()->Addr();
     GenTree* innerAddr = *addr;
-    compiler->gtPeelOffsets(&innerAddr, offset);
+
+    while (innerAddr->OperIs(GT_ADD) && innerAddr->gtGetOp2()->IsCnsIntOrI())
+    {
+        innerAddr = innerAddr->gtGetOp1();
+    }
 
     if (innerAddr->OperIs(GT_LCL_VAR))
     {

diff --git a/src/coreclr/jit/gentree.h b/src/coreclr/jit/gentree.h
@@ -1972,7 +1972,7 @@ struct GenTree
                       unsigned*             pSize     = nullptr);
 
     GenTreeLclVarCommon* IsImplicitByrefParameterValuePreMorph(Compiler* compiler);
-    GenTreeLclVar* IsImplicitByrefParameterValuePostMorph(Compiler* compiler, GenTree** addr, target_ssize_t* offset);
+    GenTreeLclVar*       IsImplicitByrefParameterValuePostMorph(Compiler* compiler, GenTree** addr);
 
     unsigned IsLclVarUpdateTree(GenTree** otherTree, genTreeOps* updateOper);
 

diff --git a/src/coreclr/jit/morph.cpp b/src/coreclr/jit/morph.cpp
@@ -3157,15 +3157,13 @@ void Compiler::fgMakeOutgoingStructArgCopy(GenTreeCall* call, CallArg* arg)
     if (opts.OptimizationEnabled() && arg->AbiInfo.PassedByRef)
     {
         GenTree*             implicitByRefLclAddr;
-        target_ssize_t       implicitByRefLclOffs;
         GenTreeLclVarCommon* implicitByRefLcl =
-            argx->IsImplicitByrefParameterValuePostMorph(this, &implicitByRefLclAddr, &implicitByRefLclOffs);
+            argx->IsImplicitByrefParameterValuePostMorph(this, &implicitByRefLclAddr);
 
         GenTreeLclVarCommon* lcl = implicitByRefLcl;
         if ((lcl == nullptr) && argx->OperIsLocal())
         {
-            lcl                  = argx->AsLclVarCommon();
-            implicitByRefLclOffs = lcl->GetLclOffs();
+            lcl = argx->AsLclVarCommon();
         }
 
         if (lcl != nullptr)
@@ -3193,28 +3191,6 @@ void Compiler::fgMakeOutgoingStructArgCopy(GenTreeCall* call, CallArg* arg)
                            !varDsc->lvPromoted && !varDsc->lvIsStructField && ((lcl->gtFlags & GTF_VAR_DEATH) != 0);
             }
 
-            // Disallow the argument from potentially aliasing the return
-            // buffer.
-            if (omitCopy)
-            {
-                GenTreeLclVarCommon* retBuffer = gtCallGetDefinedRetBufLclAddr(call);
-                if ((retBuffer != nullptr) && (retBuffer->GetLclNum() == varNum))
-                {
-                    unsigned       retBufferSize  = typGetObjLayout(call->gtRetClsHnd)->GetSize();
-                    target_ssize_t retBufferStart = retBuffer->GetLclOffs();
-                    target_ssize_t retBufferEnd   = retBufferStart + static_cast<target_ssize_t>(retBufferSize);
-
-                    unsigned       argSize        = arg->GetSignatureType() == TYP_STRUCT
-                                                        ? typGetObjLayout(arg->GetSignatureClassHandle())->GetSize()
-                                                        : genTypeSize(arg->GetSignatureType());
-                    target_ssize_t implByrefStart = implicitByRefLclOffs;
-                    target_ssize_t implByrefEnd   = implByrefStart + static_cast<target_ssize_t>(argSize);
-
-                    bool disjoint = (retBufferEnd <= implByrefStart) || (implByrefEnd <= retBufferStart);
-                    omitCopy      = disjoint;
-                }
-            }
-
             if (omitCopy)
             {
                 if (implicitByRefLcl != nullptr)
@@ -3242,7 +3218,6 @@ void Compiler::fgMakeOutgoingStructArgCopy(GenTreeCall* call, CallArg* arg)
 #endif
 
     JITDUMP("making an outgoing copy for struct arg\n");
-    assert(!call->IsTailCall() || !arg->AbiInfo.PassedByRef);
 
     CORINFO_CLASS_HANDLE copyBlkClass = arg->GetSignatureClassHandle();
     unsigned             tmp          = 0;