[PATCH] [ARM] Fix BXJ is undefined in AArch32.

[Charlie Turner]

Track the change from `SP` being unpredictable as an operand to `BXJ` in architecture pre v8-A to now being predictable.


REPOSITORY
  rL LLVM

http://reviews.llvm.org/D6842

Files:
  lib/Target/ARM/ARMInstrThumb2.td
  lib/Target/ARM/AsmParser/ARMAsmParser.cpp
  test/MC/ARM/thumb2-bxj-v8.s
  test/MC/ARM/thumb2-bxj.s

Index: lib/Target/ARM/ARMInstrThumb2.td
===================================================================
--- lib/Target/ARM/ARMInstrThumb2.td
+++ lib/Target/ARM/ARMInstrThumb2.td
@@ -3630,8 +3630,8 @@
 
 // Branch and Exchange Jazelle -- for disassembly only
 // Rm = Inst{19-16}
-def t2BXJ : T2I<(outs), (ins rGPR:$func), NoItinerary, "bxj", "\t$func", []>,
-    Sched<[WriteBr]>, Requires<[IsThumb2, IsNotMClass, PreV8]> {
+def t2BXJ : T2I<(outs), (ins GPRnopc:$func), NoItinerary, "bxj", "\t$func", []>,
+    Sched<[WriteBr]>, Requires<[IsThumb2, IsNotMClass]> {
   bits<4> func;
   let Inst{31-27} = 0b11110;
   let Inst{26} = 0;
Index: lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -6153,6 +6153,14 @@
                    "destination operands can't be identical");
     return false;
   }
+  case ARM::t2BXJ: {
+    const unsigned RmReg = Inst.getOperand(0).getReg();
+    // Rm = SP is no longer unpredictable in v8-A
+    if (RmReg == ARM::SP && !hasV8Ops())
+      return Error(Operands[2]->getStartLoc(),
+                   "r13 (SP) is an unpredictable operand to BXJ");
+    return false;
+  }
   case ARM::STRD: {
     // Rt2 must be Rt + 1.
     unsigned Rt = MRI->getEncodingValue(Inst.getOperand(0).getReg());
Index: test/MC/ARM/thumb2-bxj-v8.s
===================================================================
--- /dev/null
+++ test/MC/ARM/thumb2-bxj-v8.s
@@ -0,0 +1,11 @@
+@ RUN: not llvm-mc -triple=thumbv6t2--none-eabi -show-encoding < %s 2>&1 | FileCheck %s --check-prefix=UNDEF
+@ RUN: not llvm-mc -triple=thumbv7a--none-eabi -show-encoding < %s 2>&1  | FileCheck %s --check-prefix=UNDEF
+@ RUN: not llvm-mc -triple=thumbv7r--none-eabi -show-encoding < %s 2>&1  | FileCheck %s --check-prefix=UNDEF
+@ RUN: not llvm-mc -triple=thumbv7m--none-eabi -show-encoding < %s 2>&1  | FileCheck %s --check-prefix=ARM_MODE
+@ RUN: llvm-mc -triple=thumbv8a--none-eabi -show-encoding < %s 2>&1  | FileCheck %s
+
+bxj r13
+
+@ CHECK: bxj	sp                      @ encoding: [0xcd,0xf3,0x00,0x8f]
+@ UNDEF:  error: r13 (SP) is an unpredictable operand to BXJ
+@ ARM_MODE: error: instruction requires: arm-mode
Index: test/MC/ARM/thumb2-bxj.s
===================================================================
--- test/MC/ARM/thumb2-bxj.s
+++ test/MC/ARM/thumb2-bxj.s
@@ -1,8 +1,8 @@
 @ RUN: llvm-mc -triple=thumbv6t2--none-eabi -show-encoding < %s | FileCheck %s
 @ RUN: llvm-mc -triple=thumbv7a--none-eabi -show-encoding < %s | FileCheck %s
 @ RUN: llvm-mc -triple=thumbv7r--none-eabi -show-encoding < %s | FileCheck %s
+@ RUN: llvm-mc -triple=thumbv8a--none-eabi -show-encoding < %s | FileCheck %s
 @ RUN: not llvm-mc -triple=thumbv7m--none-eabi -show-encoding < %s 2>&1 | FileCheck %s --check-prefix=UNDEF
-@ RUN: not llvm-mc -triple=thumbv8a--none-eabi -show-encoding < %s 2>&1 | FileCheck %s --check-prefix=UNDEF
 
         bxj r2

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