[ARM] Make the assembler reject unpredictable pre/post-indexed ARM STR instructions.

The ARM ARM prohibits STR instructions with writeback into the source register. With this commit this constraint is now enforced and we stop assembling STR instructions with unpredictable behavior.

llvm-svn: 213745

diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index b62706c..5e074c4 100644 (file)
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -5728,6 +5728,19 @@ bool ARMAsmParser::validateInstruction(MCInst &Inst,
                    "source operands must be sequential");
     return false;
   }
+  case ARM::STR_PRE_IMM:
+  case ARM::STR_PRE_REG:
+  case ARM::STR_POST_IMM:
+  case ARM::STR_POST_REG: {
+    // Rt must be different from Rn.
+    const unsigned Rt = MRI->getEncodingValue(Inst.getOperand(1).getReg());
+    const unsigned Rn = MRI->getEncodingValue(Inst.getOperand(2).getReg());
+
+    if (Rt == Rn)
+      return Error(Operands[3]->getStartLoc(),
+                   "source register and base register can't be identical");
+    return false;
+  }
   case ARM::SBFX:
   case ARM::UBFX: {
     // Width must be in range [1, 32-lsb].

diff --git a/llvm/test/MC/ARM/diagnostics.s b/llvm/test/MC/ARM/diagnostics.s
index 88c5fb5..e26566d 100644 (file)
--- a/llvm/test/MC/ARM/diagnostics.s
+++ b/llvm/test/MC/ARM/diagnostics.s
@@ -491,3 +491,20 @@ foo2:
 @ CHECK-ERRORS:                 ^
 @ CHECK-ERRORS: error: immediate expression for mov requires :lower16: or :upper16
 @ CHECK-ERRORS:                  ^
+
+        str r0, [r0, #4]!
+        str r0, [r0, r1]!
+        str r0, [r0], #4
+        str r0, [r0], r1
+@ CHECK-ERRORS: error: source register and base register can't be identical
+@ CHECK-ERRORS: str r0, [r0, #4]!
+@ CHECK-ERRORS:         ^
+@ CHECK-ERRORS: error: source register and base register can't be identical
+@ CHECK-ERRORS: str r0, [r0, r1]!
+@ CHECK-ERRORS:         ^
+@ CHECK-ERRORS: error: source register and base register can't be identical
+@ CHECK-ERRORS: str r0, [r0], #4
+@ CHECK-ERRORS:         ^
+@ CHECK-ERRORS: error: source register and base register can't be identical
+@ CHECK-ERRORS: str r0, [r0], r1
+@ CHECK-ERRORS:         ^