From df7e0218205ea8dbd1275a9ac04c114ca745e372 Mon Sep 17 00:00:00 2001
From: Reid Kleckner <rnk@google.com>
Date: Tue, 15 Jan 2019 01:24:18 +0000
Subject: [PATCH] [X86] Avoid clobbering ESP/RSP in the epilogue.

Summary:
In r345197 ESP and RSP were added to GR32_TC/GR64_TC, allowing them to
be used for tail calls, but this also caused `findDeadCallerSavedReg` to
think they were acceptable targets for clobbering. Filter them out.

Fixes PR40289.

Patch by Geoffry Song!

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D56617

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351146 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86FrameLowering.cpp |  3 ++-
 test/CodeGen/X86/pr40289-64bit.ll   | 10 ++++++++++
 test/CodeGen/X86/pr40289.ll         | 10 ++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/X86/pr40289-64bit.ll
 create mode 100644 test/CodeGen/X86/pr40289.ll

diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index d722c75c4f0..984db12201e 100644
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/lib/Target/X86/X86FrameLowering.cpp
@@ -185,7 +185,8 @@ static unsigned findDeadCallerSavedReg(MachineBasicBlock &MBB,
     }
 
     for (auto CS : AvailableRegs)
-      if (!Uses.count(CS) && CS != X86::RIP)
+      if (!Uses.count(CS) && CS != X86::RIP && CS != X86::RSP &&
+          CS != X86::ESP)
         return CS;
   }
   }
diff --git a/test/CodeGen/X86/pr40289-64bit.ll b/test/CodeGen/X86/pr40289-64bit.ll
new file mode 100644
index 00000000000..fd7e2d55bdc
--- /dev/null
+++ b/test/CodeGen/X86/pr40289-64bit.ll
@@ -0,0 +1,10 @@
+; RUN: llc < %s -mtriple=x86_64-pc-windows-msvc | FileCheck %s
+
+define cc 92 < 9 x i64 > @clobber() {
+  %1 = alloca i64
+  %2 = load volatile i64, i64* %1
+  ret < 9 x i64 > undef
+  ; CHECK-LABEL: clobber:
+  ; CHECK-NOT: popq %rsp
+  ; CHECK: addq $8, %rsp
+}
diff --git a/test/CodeGen/X86/pr40289.ll b/test/CodeGen/X86/pr40289.ll
new file mode 100644
index 00000000000..abcb5fa41fa
--- /dev/null
+++ b/test/CodeGen/X86/pr40289.ll
@@ -0,0 +1,10 @@
+; RUN: llc < %s -mtriple=i686-pc-windows-msvc | FileCheck %s
+
+define < 3 x i32 > @clobber() {
+  %1 = alloca i32
+  %2 = load volatile i32, i32* %1
+  ret < 3 x i32 > undef
+  ; CHECK-LABEL: clobber:
+  ; CHECK-NOT: popl %esp
+  ; CHECK: addl $4, %esp
+}