From c22d94f239f355dade0a71fc9a6e019e037d6747 Mon Sep 17 00:00:00 2001
From: Eugene Rozenfeld <erozen@microsoft.com>
Date: Sat, 30 May 2020 16:34:19 -0700
Subject: [PATCH] Fix fast tail calls on Windows ARM64. (#37192)

LowerFastTailCall has code that looks for incoming stack arguments
that may be overwritten by outgoing stack arguments and copies
them to a temp. The logic was incorrect for Windows Arm64 because it was
assuming shadow space, which only exists in Windows x64 abi.

Fixes #31729.
Fixes #36911.
---
 src/coreclr/src/jit/lower.cpp    | 6 +++---
 src/coreclr/tests/issues.targets | 6 ------
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/coreclr/src/jit/lower.cpp b/src/coreclr/src/jit/lower.cpp
index 75d63a18661f7..07d15696de9b1 100644
--- a/src/coreclr/src/jit/lower.cpp
+++ b/src/coreclr/src/jit/lower.cpp
@@ -1870,7 +1870,7 @@ void Lowering::LowerFastTailCall(GenTreeCall* call)
 
             unsigned int overwrittenStart = put->getArgOffset();
             unsigned int overwrittenEnd   = overwrittenStart + put->getArgSize();
-#if !(defined(TARGET_WINDOWS) && defined(TARGET_64BIT))
+#if !(defined(TARGET_WINDOWS) && defined(TARGET_AMD64))
             int baseOff = -1; // Stack offset of first arg on stack
 #endif
 
@@ -1883,8 +1883,8 @@ void Lowering::LowerFastTailCall(GenTreeCall* call)
                     continue;
                 }
 
-#if defined(TARGET_WINDOWS) && defined(TARGET_64BIT)
-                // On Win64, the argument position determines the stack slot uniquely, and even the
+#if defined(TARGET_WINDOWS) && defined(TARGET_AMD64)
+                // On Windows x64, the argument position determines the stack slot uniquely, and even the
                 // register args take up space in the stack frame (shadow space).
                 unsigned int argStart = callerArgLclNum * TARGET_POINTER_SIZE;
                 unsigned int argEnd   = argStart + static_cast<unsigned int>(callerArgDsc->lvArgStackSize());
diff --git a/src/coreclr/tests/issues.targets b/src/coreclr/tests/issues.targets
index da519144b070e..ed9731338b968 100644
--- a/src/coreclr/tests/issues.targets
+++ b/src/coreclr/tests/issues.targets
@@ -597,12 +597,6 @@
         <ExcludeList Include="$(XunitTestBinBase)/JIT/opt/Tailcall/TailcallVerifyWithPrefix/*">
             <Issue>Condition17::Test1 checks that we tail call via helper when security cookie is needed; on arm64 we fast tail call in this case.</Issue>
         </ExcludeList>
-        <ExcludeList Include="$(XunitTestBinBase)/JIT/Stress/ABI/tailcalls_d/*">
-            <Issue>https://github.com/dotnet/runtime/issues/31729</Issue>
-        </ExcludeList>
-        <ExcludeList Include="$(XunitTestBinBase)/JIT/Stress/ABI/tailcalls_do/*">
-            <Issue>https://github.com/dotnet/runtime/issues/31729</Issue>
-        </ExcludeList>
         <ExcludeList Include="$(XunitTestBinBase)/GC/Regressions/dev10bugs/536168/536168/*">
             <Issue>extremely memory/time intensive test</Issue>
         </ExcludeList>