JIT: fix morph tail call copy opt alias analysis (#57009)

If there are non-call references to an implicit byref local, disqualify
that local from morph tail call copy optimization.

The fix is conservative in that "harmless" non-call references like field
accesses will also disqualify the opt. This can be improved on with extra
analysis in local morph.

Closes #56734.

diff --git a/src/coreclr/jit/lclmorph.cpp b/src/coreclr/jit/lclmorph.cpp
index 349c5ef..caa8a1b 100644 (file)
--- a/src/coreclr/jit/lclmorph.cpp
+++ b/src/coreclr/jit/lclmorph.cpp
@@ -1184,7 +1184,7 @@ private:
 
         if (isArgToCall)
         {
-            JITDUMP("LocalAddressVisitor incrementing weighted ref count from %d to %d"
+            JITDUMP("LocalAddressVisitor incrementing weighted ref count from " FMT_WT " to " FMT_WT
                     " for implicit by-ref V%02d arg passed to call\n",
                     varDsc->lvRefCntWtd(RCS_EARLY), varDsc->lvRefCntWtd(RCS_EARLY) + 1, lclNum);
             varDsc->incLvRefCntWtd(1, RCS_EARLY);

diff --git a/src/coreclr/jit/morph.cpp b/src/coreclr/jit/morph.cpp
index d23fea5..a00b4bb 100644 (file)
--- a/src/coreclr/jit/morph.cpp
+++ b/src/coreclr/jit/morph.cpp
@@ -7118,13 +7118,29 @@ bool Compiler::fgCallHasMustCopyByrefParameter(GenTreeCall* callee)
                             // We only check this for calls with small numbers of arguments,
                             // as the analysis cost will be quadratic.
                             //
-                            if (varDsc->lvRefCnt(RCS_EARLY) == 1)
+                            const unsigned totalAppearances = varDsc->lvRefCnt(RCS_EARLY);
+                            const unsigned callAppearances  = (unsigned)varDsc->lvRefCntWtd(RCS_EARLY);
+                            assert(totalAppearances >= callAppearances);
+
+                            if (totalAppearances == 1)
                             {
                                 JITDUMP("... yes, arg is the only appearance of V%02u\n", lclNum);
                                 hasMustCopyByrefParameter = false;
                             }
+                            else if (totalAppearances > callAppearances)
+                            {
+                                // lvRefCntWtd tracks the number of appearances of the arg at call sites.
+                                // If this number doesn't match the regular ref count, there is
+                                // a non-call appearance, and we must be conservative.
+                                //
+                                JITDUMP("... no, arg has %u non-call appearance(s)\n",
+                                        totalAppearances - callAppearances);
+                            }
                             else if (argInfo->ArgCount() <= argLimit)
                             {
+                                JITDUMP("... all %u appearance(s) are as implicit byref args to calls.\n"
+                                        "... Running alias analysis on this call's args\n",
+                                        totalAppearances);
                                 GenTree* interferingArg = nullptr;
                                 for (unsigned index2 = 0; index2 < argInfo->ArgCount(); ++index2)
                                 {

diff --git a/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_0.cs b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_0.cs
new file mode 100644 (file)
index 0000000..8140262
--- /dev/null
+++ b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_0.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+class Runtime_56743_0
+{
+    [MethodImpl(MethodImplOptions.NoOptimization)]
+    static int Main()
+    {
+        int result = Foo(default, default);
+        return result == 0 ? 100 : -1;
+    }
+
+    static int Foo(S s, Span<S> span)
+    {
+        span = MemoryMarshal.CreateSpan(ref s, 1);
+        return Bar(s, span);
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static int Bar(S h, Span<S> s)
+    {
+        s[0].A = 10;
+        return h.A;
+    }
+
+    struct S
+    {
+        public int A, B, C, D;
+    }
+}

diff --git a/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_0.csproj b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_0.csproj
new file mode 100644 (file)
index 0000000..f3e1cbd
--- /dev/null
+++ b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_0.csproj
@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+  </PropertyGroup>
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>

diff --git a/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_1.cs b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_1.cs
new file mode 100644 (file)
index 0000000..32bfb85
--- /dev/null
+++ b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_1.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+
+unsafe class Runtime_56743_1
+{
+    [MethodImpl(MethodImplOptions.NoOptimization)]
+    static int Main()
+    {
+        int result = Foo(default);
+        return result == 0 ? 100 : -1;
+    }
+
+    static S* s_s;
+    static int Foo(S s)
+    {
+        s_s = &s;
+        return Bar(s);
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static int Bar(S h)
+    {
+        s_s->A = 10;
+        return h.A;
+    }
+
+    struct S
+    {
+        public int A, B, C, D;
+    }
+}

diff --git a/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_1.csproj b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_1.csproj
new file mode 100644 (file)
index 0000000..bf6f589
--- /dev/null
+++ b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_1.csproj
@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+  </PropertyGroup>
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>

diff --git a/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_2.cs b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_2.cs
new file mode 100644 (file)
index 0000000..b258e9e
--- /dev/null
+++ b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_2.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+
+unsafe class Runtime_56743_2
+{
+    [MethodImpl(MethodImplOptions.NoOptimization)]
+    static int Main()
+    {
+        int result = Foo(default);
+        return result == 0 ? 100 : -1;
+    }
+
+    static int Foo(S h)
+    {
+        h.H = &h;
+        return Bar(h);
+    }
+    
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static int Bar(S h)
+    {
+        h.H->A = 10;
+        return h.A;
+    }
+    
+    unsafe struct S
+    {
+        public int A, B;
+        public S* H;
+    }
+}

diff --git a/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_2.csproj b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_2.csproj
new file mode 100644 (file)
index 0000000..bf6f589
--- /dev/null
+++ b/src/tests/JIT/Regression/JitBlue/Runtime_56743/Runtime_56743_2.csproj
@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+  </PropertyGroup>
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>