From 54646a2723c032c7ed1d35efb1235b552cc80966 Mon Sep 17 00:00:00 2001
From: Martin Storsjo <martin@martin.st>
Date: Thu, 28 Sep 2017 19:04:30 +0000
Subject: [PATCH] [ARM] Restore the right frame pointer register in
 Int_eh_sjlj_longjmp

In setupEntryBlockAndCallSites in CodeGen/SjLjEHPrepare.cpp,
we fetch and store the actual frame pointer, but on return via
the longjmp intrinsic, it always was restored into the r7 variable.

On windows, the frame pointer should be restored into r11 instead of r7.

On Darwin (where sjlj exception handling is used by default), the frame
pointer is always r7, both in arm and thumb mode, and likewise, on
windows, the frame pointer always is r11.

On linux however, if sjlj exception handling is enabled (which it isn't
by default), libcxxabi and the user code can be built in differing modes
using different registers as frame pointer. Therefore, when restoring
registers on a platform where we don't always use the same register
depending on code mode, restore both r7 and r11.

Differential Revision: https://reviews.llvm.org/D38253

llvm-svn: 314451
---
 lib/Target/ARM/ARMAsmPrinter.cpp   | 72 ++++++++++++++++++++++++------
 test/CodeGen/ARM/setjmp_longjmp.ll | 12 +++++
 2 files changed, 70 insertions(+), 14 deletions(-)

diff --git a/lib/Target/ARM/ARMAsmPrinter.cpp b/lib/Target/ARM/ARMAsmPrinter.cpp
index 13335a84f6d..2147c1cfcf8 100644
--- a/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -1204,6 +1204,10 @@ void ARMAsmPrinter::EmitInstruction(const MachineInstr *MI) {
   MCTargetStreamer &TS = *OutStreamer->getTargetStreamer();
   ARMTargetStreamer &ATS = static_cast<ARMTargetStreamer &>(TS);
 
+  const MachineFunction &MF = *MI->getParent()->getParent();
+  const ARMSubtarget &STI = MF.getSubtarget<ARMSubtarget>();
+  unsigned FramePtr = STI.useR7AsFramePointer() ? ARM::R7 : ARM::R11;
+
   // If we just ended a constant pool, mark it as such.
   if (InConstantPool && MI->getOpcode() != ARM::CONSTPOOL_ENTRY) {
     OutStreamer->EmitDataRegion(MCDR_DataRegionEnd);
@@ -1884,13 +1888,33 @@ void ARMAsmPrinter::EmitInstruction(const MachineInstr *MI) {
       .addImm(ARMCC::AL)
       .addReg(0));
 
-    EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::LDRi12)
-      .addReg(ARM::R7)
-      .addReg(SrcReg)
-      .addImm(0)
-      // Predicate.
-      .addImm(ARMCC::AL)
-      .addReg(0));
+    if (STI.isTargetDarwin() || STI.isTargetWindows()) {
+      // These platforms always use the same frame register
+      EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::LDRi12)
+        .addReg(FramePtr)
+        .addReg(SrcReg)
+        .addImm(0)
+        // Predicate.
+        .addImm(ARMCC::AL)
+        .addReg(0));
+    } else {
+      // If the calling code might use either R7 or R11 as
+      // frame pointer register, restore it into both.
+      EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::LDRi12)
+        .addReg(ARM::R7)
+        .addReg(SrcReg)
+        .addImm(0)
+        // Predicate.
+        .addImm(ARMCC::AL)
+        .addReg(0));
+      EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::LDRi12)
+        .addReg(ARM::R11)
+        .addReg(SrcReg)
+        .addImm(0)
+        // Predicate.
+        .addImm(ARMCC::AL)
+        .addReg(0));
+    }
 
     assert(Subtarget->hasV4TOps());
     EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::BX)
@@ -1934,13 +1958,33 @@ void ARMAsmPrinter::EmitInstruction(const MachineInstr *MI) {
       .addImm(ARMCC::AL)
       .addReg(0));
 
-    EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::tLDRi)
-      .addReg(ARM::R7)
-      .addReg(SrcReg)
-      .addImm(0)
-      // Predicate.
-      .addImm(ARMCC::AL)
-      .addReg(0));
+    if (STI.isTargetDarwin() || STI.isTargetWindows()) {
+      // These platforms always use the same frame register
+      EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::tLDRi)
+        .addReg(FramePtr)
+        .addReg(SrcReg)
+        .addImm(0)
+        // Predicate.
+        .addImm(ARMCC::AL)
+        .addReg(0));
+    } else {
+      // If the calling code might use either R7 or R11 as
+      // frame pointer register, restore it into both.
+      EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::tLDRi)
+        .addReg(ARM::R7)
+        .addReg(SrcReg)
+        .addImm(0)
+        // Predicate.
+        .addImm(ARMCC::AL)
+        .addReg(0));
+      EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::tLDRi)
+        .addReg(ARM::R11)
+        .addReg(SrcReg)
+        .addImm(0)
+        // Predicate.
+        .addImm(ARMCC::AL)
+        .addReg(0));
+    }
 
     EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::tBX)
       .addReg(ScratchReg)
diff --git a/test/CodeGen/ARM/setjmp_longjmp.ll b/test/CodeGen/ARM/setjmp_longjmp.ll
index 7100175a97a..37ef1f43519 100644
--- a/test/CodeGen/ARM/setjmp_longjmp.ll
+++ b/test/CodeGen/ARM/setjmp_longjmp.ll
@@ -1,4 +1,6 @@
 ; RUN: llc %s -o - | FileCheck %s
+; RUN: llc -mtriple=armv7-linux -exception-model sjlj %s -o - | FileCheck %s -check-prefix CHECK-LINUX
+; RUN: llc -mtriple=thumbv7-win32 -exception-model sjlj %s -o - | FileCheck %s -check-prefix CHECK-WIN32
 target triple = "armv7-apple-ios"
 
 declare i32 @llvm.eh.sjlj.setjmp(i8*)
@@ -28,6 +30,16 @@ declare i8* @llvm.stacksave()
 ; CHECK-NEXT: ldr [[DESTREG:r[0-9]+]], {{\[}}[[BUFREG]], #4]
 ; CHECK-NEXT: ldr r7, {{\[}}[[BUFREG]]{{\]}}
 ; CHECK-NEXT: bx [[DESTREG]]
+
+; CHECK-LINUX: ldr sp, [{{\s*}}[[BUFREG:r[0-9]+]], #8]
+; CHECK-LINUX-NEXT: ldr [[DESTREG:r[0-9]+]], {{\[}}[[BUFREG]], #4]
+; CHECK-LINUX-NEXT: ldr r7, {{\[}}[[BUFREG]]{{\]}}
+; CHECK-LINUX-NEXT: ldr r11, {{\[}}[[BUFREG]]{{\]}}
+; CHECK-LINUX-NEXT: bx [[DESTREG]]
+
+; CHECK-WIN32: ldr.w r11, [{{\s*}}[[BUFREG:r[0-9]+]]]
+; CHECK-WIN32-NEXT: ldr.w sp, {{\[}}[[BUFREG]], #8]
+; CHECK-WIN32-NEXT: ldr.w pc, {{\[}}[[BUFREG]], #4]
 define void @foobar() {
 entry:
   %buf = alloca [5 x i8*], align 4