From bf3e78f5728f116067f8a373a522c221ccdaa08f Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <compnerd@compnerd.org>
Date: Sun, 18 May 2014 04:12:52 +0000
Subject: [PATCH] ARM: improve WoA ABI conformance for frame register

Windows on ARM uses R11 for the frame pointer even though the environment is a
pure Thumb-2, thumb-only environment.  Replicate this behaviour to improve
Windows ABI compatibility.  This register is used for fast stack walking, and
thus is part of the Windows ABI.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209085 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMBaseRegisterInfo.cpp     | 10 ++++--
 test/CodeGen/ARM/Windows/frame-register.ll | 22 +++++++++++++
 test/CodeGen/ARM/frame-register.ll         | 38 ++++++++++++++++++++++
 3 files changed, 67 insertions(+), 3 deletions(-)
 create mode 100644 test/CodeGen/ARM/Windows/frame-register.ll
 create mode 100644 test/CodeGen/ARM/frame-register.ll

diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index 9548dd50b23..a2eee9ff304 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -44,9 +44,13 @@
 using namespace llvm;
 
 ARMBaseRegisterInfo::ARMBaseRegisterInfo(const ARMSubtarget &sti)
-  : ARMGenRegisterInfo(ARM::LR, 0, 0, ARM::PC), STI(sti),
-    FramePtr((STI.isTargetMachO() || STI.isThumb()) ? ARM::R7 : ARM::R11),
-    BasePtr(ARM::R6) {
+    : ARMGenRegisterInfo(ARM::LR, 0, 0, ARM::PC), STI(sti), BasePtr(ARM::R6) {
+  if (STI.isTargetMachO())
+    FramePtr = ARM::R7;
+  else if (STI.isTargetWindows())
+    FramePtr = ARM::R11;
+  else // ARM EABI
+    FramePtr = STI.isThumb() ? ARM::R7 : ARM::R11;
 }
 
 const MCPhysReg*
diff --git a/test/CodeGen/ARM/Windows/frame-register.ll b/test/CodeGen/ARM/Windows/frame-register.ll
new file mode 100644
index 00000000000..31167d7352e
--- /dev/null
+++ b/test/CodeGen/ARM/Windows/frame-register.ll
@@ -0,0 +1,22 @@
+; RUN: llc -mtriple thumbv7-windows -disable-fp-elim -filetype asm -o - %s \
+; RUN:     | FileCheck %s
+
+declare void @callee(i32)
+
+define i32 @calleer(i32 %i) {
+entry:
+  %i.addr = alloca i32, align 4
+  %j = alloca i32, align 4
+  store i32 %i, i32* %i.addr, align 4
+  %0 = load i32* %i.addr, align 4
+  %add = add nsw i32 %0, 1
+  store i32 %add, i32* %j, align 4
+  %1 = load i32* %j, align 4
+  call void @callee(i32 %1)
+  %2 = load i32* %j, align 4
+  %add1 = add nsw i32 %2, 1
+  ret i32 %add1
+}
+
+; CHECK: push.w {r11, lr}
+
diff --git a/test/CodeGen/ARM/frame-register.ll b/test/CodeGen/ARM/frame-register.ll
new file mode 100644
index 00000000000..e6a55bddaf1
--- /dev/null
+++ b/test/CodeGen/ARM/frame-register.ll
@@ -0,0 +1,38 @@
+; RUN: llc -mtriple arm-eabi -disable-fp-elim -filetype asm -o - %s \
+; RUN:     | FileCheck -check-prefix CHECK-ARM %s
+
+; RUN: llc -mtriple thumb-eabi -disable-fp-elim -filetype asm -o - %s \
+; RUN:     | FileCheck -check-prefix CHECK-THUMB %s
+
+; RUN: llc -mtriple arm-darwin -disable-fp-elim -filetype asm -o - %s \
+; RUN:     | FileCheck -check-prefix CHECK-DARWIN-ARM %s
+
+; RUN: llc -mtriple thumb-darwin -disable-fp-elim -filetype asm -o - %s \
+; RUN:     | FileCheck -check-prefix CHECK-DARWIN-THUMB %s
+
+declare void @callee(i32)
+
+define i32 @calleer(i32 %i) {
+entry:
+  %i.addr = alloca i32, align 4
+  %j = alloca i32, align 4
+  store i32 %i, i32* %i.addr, align 4
+  %0 = load i32* %i.addr, align 4
+  %add = add nsw i32 %0, 1
+  store i32 %add, i32* %j, align 4
+  %1 = load i32* %j, align 4
+  call void @callee(i32 %1)
+  %2 = load i32* %j, align 4
+  %add1 = add nsw i32 %2, 1
+  ret i32 %add1
+}
+
+; CHECK-ARM: push {r11, lr}
+; CHECK-ARM: mov r11, sp
+
+; CHECK-THUMB: push {r4, r6, r7, lr}
+; CHECK-THUMB: add r7, sp, #8
+
+; CHECK-DARWIN-ARM: push {r7, lr}
+; CHECK-DARWIN-THUMB: push {r4, r7, lr}
+