From 6af366be8ad3199f715c54e84c779e02bb8c18b8 Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Tue, 23 Apr 2019 13:50:13 +0000
Subject: [PATCH] ARM: disallow add/sub to sp unless Rn is also sp.

The manual says that Thumb2 add/sub instructions are only allowed to modify sp
if the first source is also sp. This is slightly different from the usual rGPR
restriction since it's context-sensitive, so implement it in C++.

llvm-svn: 358987
---
 llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp     | 14 ++++++++++
 .../Target/ARM/Disassembler/ARMDisassembler.cpp    | 14 +++++++++-
 llvm/test/MC/ARM/invalid-addsub.s                  | 20 ++++++++++++++
 llvm/test/MC/Disassembler/ARM/invalid-thumbv7.txt  | 31 ++++++++++++++++++++++
 4 files changed, 78 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/MC/ARM/invalid-addsub.s

diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 65c6a56..9bc232a 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -6792,6 +6792,20 @@ bool ARMAsmParser::validateInstruction(MCInst &Inst,
     }
     break;
 
+  case ARM::t2ADDri:
+  case ARM::t2ADDri12:
+  case ARM::t2ADDrr:
+  case ARM::t2ADDrs:
+  case ARM::t2SUBri:
+  case ARM::t2SUBri12:
+  case ARM::t2SUBrr:
+  case ARM::t2SUBrs:
+    if (Inst.getOperand(0).getReg() == ARM::SP &&
+        Inst.getOperand(1).getReg() != ARM::SP)
+      return Error(Operands[4]->getStartLoc(),
+                   "source register must be sp if destination is sp");
+    break;
+
   // Final range checking for Thumb unconditional branch instructions.
   case ARM::tB:
     if (!(static_cast<ARMOperand &>(*Operands[2])).isSignedOffset<11, 1>())
diff --git a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index e92bcc5..7a8d9b0 100644
--- a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -441,6 +441,18 @@ static DecodeStatus checkDecodedInstruction(MCInst &MI, uint64_t &Size,
         return MCDisassembler::SoftFail;
       return Result;
     }
+    case ARM::t2ADDri:
+    case ARM::t2ADDri12:
+    case ARM::t2ADDrr:
+    case ARM::t2ADDrs:
+    case ARM::t2SUBri:
+    case ARM::t2SUBri12:
+    case ARM::t2SUBrr:
+    case ARM::t2SUBrs:
+      if (MI.getOperand(0).getReg() == ARM::SP &&
+          MI.getOperand(1).getReg() != ARM::SP)
+        return MCDisassembler::SoftFail;
+      return Result;
     default: return Result;
   }
 }
@@ -772,7 +784,7 @@ DecodeStatus ThumbDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
   if (Result != MCDisassembler::Fail) {
     Size = 4;
     Check(Result, AddThumbPredicate(MI));
-    return Result;
+    return checkDecodedInstruction(MI, Size, Address, OS, CS, Insn32, Result);
   }
 
   if (fieldFromInstruction(Insn32, 28, 4) == 0xE) {
diff --git a/llvm/test/MC/ARM/invalid-addsub.s b/llvm/test/MC/ARM/invalid-addsub.s
new file mode 100644
index 0000000..07c1a80
--- /dev/null
+++ b/llvm/test/MC/ARM/invalid-addsub.s
@@ -0,0 +1,20 @@
+@ RUN: not llvm-mc -triple thumbv7-apple-ios %s -o - 2>&1 | FileCheck %s
+
+@ CHECK: error: source register must be sp if destination is sp
+@ CHECK: error: source register must be sp if destination is sp
+@ CHECK: error: source register must be sp if destination is sp
+@ CHECK: error: source register must be sp if destination is sp
+add sp, r5, #1
+addw sp, r7, #4
+add sp, r3, r2
+add sp, r3, r5, lsl #3
+
+
+@ CHECK: error: source register must be sp if destination is sp
+@ CHECK: error: source register must be sp if destination is sp
+@ CHECK: error: source register must be sp if destination is sp
+@ CHECK: error: source register must be sp if destination is sp
+sub sp, r5, #1
+subw sp, r7, #4
+sub sp, r3, r2
+sub sp, r3, r5, lsl #3
diff --git a/llvm/test/MC/Disassembler/ARM/invalid-thumbv7.txt b/llvm/test/MC/Disassembler/ARM/invalid-thumbv7.txt
index e295ed3..48b5b8b 100644
--- a/llvm/test/MC/Disassembler/ARM/invalid-thumbv7.txt
+++ b/llvm/test/MC/Disassembler/ARM/invalid-thumbv7.txt
@@ -394,3 +394,34 @@
 [0xff,0xf3,0x30,0x80]
 # CHECK: invalid instruction encoding
 # CHECK-NEXT: [0xff,0xf3,0x30,0x80]
+
+#------------------------------------------------------------------------------
+# If dest is sp then source must be in T2 add/sub
+#------------------------------------------------------------------------------
+
+[0x05,0xf1,0x01,0x0d]
+[0x07,0xf2,0x04,0x0d]
+[0x03,0xeb,0x02,0x0d]
+[0x03,0xeb,0xc5,0x0d]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0x05,0xf1,0x01,0x0d]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0x07,0xf2,0x04,0x0d]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0x03,0xeb,0x02,0x0d]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0x03,0xeb,0xc5,0x0d]
+
+
+[0xa5,0xf1,0x01,0x0d]
+[0xa7,0xf2,0x04,0x0d]
+[0xa3,0xeb,0x02,0x0d]
+[0xa3,0xeb,0xc5,0x0d]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0xa5,0xf1,0x01,0x0d]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0xa7,0xf2,0x04,0x0d]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0xa3,0xeb,0x02,0x0d]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0xa3,0xeb,0xc5,0x0d]
-- 
2.7.4