From 4a5b076253a0f1e3d51c9a9c6cec384a19f40718 Mon Sep 17 00:00:00 2001
From: Florian Hahn <florian.hahn@arm.com>
Date: Wed, 18 Jan 2017 15:01:22 +0000
Subject: [PATCH] [thumb,framelowering] Reset NoVRegs in
 Thumb1FrameLowering::emitPrologue.

Summary:
In this function, virtual registers can be introduced (for example
through calls to emitThumbRegPlusImmInReg). doScavengeFrameVirtualRegs
will replace those virtual registers with concrete registers later on
in PrologEpilogInserter, which sets NoVRegs again.

This patch fixes the Codegen/Thumb/segmented-stacks.ll test case which
failed with expensive checks.
https://llvm.org/bugs/show_bug.cgi?id=27484


Reviewers: rnk, bkramer, olista01

Reviewed By: olista01

Subscribers: llvm-commits, rengolin

Differential Revision: https://reviews.llvm.org/D28829

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292372 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/PrologEpilogInserter.cpp   | 2 ++
 lib/Target/ARM/Thumb1FrameLowering.cpp | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp
index 5fca7fa5536..708f95c55b2 100644
--- a/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/lib/CodeGen/PrologEpilogInserter.cpp
@@ -1237,4 +1237,6 @@ doScavengeFrameVirtualRegs(MachineFunction &MF, RegScavenger *RS) {
         ++I;
     }
   }
+
+  MF.getProperties().set(MachineFunctionProperties::Property::NoVRegs);
 }
diff --git a/lib/Target/ARM/Thumb1FrameLowering.cpp b/lib/Target/ARM/Thumb1FrameLowering.cpp
index 1103532075a..3cfe61b738d 100644
--- a/lib/Target/ARM/Thumb1FrameLowering.cpp
+++ b/lib/Target/ARM/Thumb1FrameLowering.cpp
@@ -347,6 +347,10 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF,
   // checks for hasVarSizedObjects.
   if (MFI.hasVarSizedObjects())
     AFI->setShouldRestoreSPFromFP(true);
+
+  // In some cases, virtual registers have been introduced, e.g. by uses of
+  // emitThumbRegPlusImmInReg.
+  MF.getProperties().reset(MachineFunctionProperties::Property::NoVRegs);
 }
 
 static bool isCSRestore(MachineInstr &MI, const MCPhysReg *CSRegs) {
-- 
2.50.1