From c02b237e467c825d23cda36e178abf769629c9d0 Mon Sep 17 00:00:00 2001
From: Bjorn Steinbrink <bsteinbr@gmail.com>
Date: Tue, 7 Nov 2017 08:50:21 +0000
Subject: [PATCH] [X86] Don't clobber reserved registers with stack adjustments

Summary:
Calls using invoke in funclet based functions are assumed to clobber
all registers, which causes the stack adjustment using pops to consider
all registers not defined by the call to be undefined, which can
unfortunately include the base pointer, if one is needed.

To prevent this (and possibly other hazards), skip reserved registers
when looking for candidate registers.

This fixes issue #45034 in the Rust compiler.

Reviewers: mkuper

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D39636

llvm-svn: 317551
---
 llvm/lib/Target/X86/X86FrameLowering.cpp        |  5 +++++
 llvm/test/CodeGen/X86/pop-stack-cleanup-msvc.ll | 26 +++++++++++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 llvm/test/CodeGen/X86/pop-stack-cleanup-msvc.ll

diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 988f296..c7af0ae 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -2577,6 +2577,7 @@ bool X86FrameLowering::adjustStackWithPops(MachineBasicBlock &MBB,
   unsigned Regs[2];
   unsigned FoundRegs = 0;
 
+  auto &MRI = MBB.getParent()->getRegInfo();
   auto RegMask = Prev->getOperand(1);
 
   auto &RegClass =
@@ -2590,6 +2591,10 @@ bool X86FrameLowering::adjustStackWithPops(MachineBasicBlock &MBB,
     if (!RegMask.clobbersPhysReg(Candidate))
       continue;
 
+    // Don't clobber reserved registers
+    if (MRI.isReserved(Candidate))
+      continue;
+
     bool IsDef = false;
     for (const MachineOperand &MO : Prev->implicit_operands()) {
       if (MO.isReg() && MO.isDef() &&
diff --git a/llvm/test/CodeGen/X86/pop-stack-cleanup-msvc.ll b/llvm/test/CodeGen/X86/pop-stack-cleanup-msvc.ll
new file mode 100644
index 0000000..6330d3d
--- /dev/null
+++ b/llvm/test/CodeGen/X86/pop-stack-cleanup-msvc.ll
@@ -0,0 +1,26 @@
+; RUN: llc < %s | FileCheck %s
+
+target triple = "i686--windows-msvc"
+
+declare { i8*, i32 } @param2_ret2(i32, i32)
+declare i32 @__CxxFrameHandler3(...)
+
+
+define void @test_reserved_regs() minsize optsize personality i32 (...)* @__CxxFrameHandler3 {
+; CHECK-LABEL: test_reserved_regs:
+; CHECK: calll _param2_ret2
+; CHECK-NEXT: popl %ecx
+; CHECK-NEXT: popl %edi
+start:
+  %s = alloca i64
+  store i64 4, i64* %s
+  %0 = invoke { i8*, i32 } @param2_ret2(i32 0, i32 1)
+          to label %out unwind label %cleanup
+
+out:
+  ret void
+
+cleanup:
+  %cp = cleanuppad within none []
+  cleanupret from %cp unwind to caller
+}
-- 
2.7.4