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-rw-r--r--lib/Target/ARM/Disassembler/ARMDisassembler.cpp2
-rw-r--r--test/MC/Disassembler/ARM/invalid-LDRB_POST-arm.txt5
2 files changed, 4 insertions, 3 deletions
diff --git a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index 8a85cfade1..85e48c7165 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -978,6 +978,8 @@ static bool DecodeAddrMode2IdxInstruction(llvm::MCInst &Inst, unsigned Insn,
else if (!P && writeback)
idx_mode = ARMII::IndexModePost;
+ if (writeback && (Rn == 15 || Rn == Rt)) return false; // UNPREDICTABLE
+
if (reg) {
if (!DecodeGPRnopcRegisterClass(Inst, Rm, Address, Decoder)) return false;
ARM_AM::ShiftOpc Opc = ARM_AM::lsl;
diff --git a/test/MC/Disassembler/ARM/invalid-LDRB_POST-arm.txt b/test/MC/Disassembler/ARM/invalid-LDRB_POST-arm.txt
index 032021362d..61d10b0f65 100644
--- a/test/MC/Disassembler/ARM/invalid-LDRB_POST-arm.txt
+++ b/test/MC/Disassembler/ARM/invalid-LDRB_POST-arm.txt
@@ -1,11 +1,10 @@
# RUN: llvm-mc --disassemble %s -triple=arm-apple-darwin9 |& grep {invalid instruction encoding}
-# XFAIL: *
# Opcode=140 Name=LDRB_POST Format=ARM_FORMAT_LDFRM(6)
-# 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
+# 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
# -------------------------------------------------------------------------------------------------
# | 1: 1: 1: 0| 0: 1: 1: 0| 1: 1: 0: 1| 0: 1: 1: 1| 0: 1: 1: 1| 0: 0: 0: 0| 0: 0: 0: 0| 0: 1: 0: 1|
# -------------------------------------------------------------------------------------------------
-#
+#
# if wback && (n == 15 || n == t) then UNPREDICTABLE
0x05 0x70 0xd7 0xe6