[ARM] Diagnose PC-writing instructions in IT blocks

In Thumb2, instructions which write to the PC are UNPREDICTABLE if they are in
an IT block but not the last instruction in the block.

Previously, we only diagnosed this for LDM instructions, this patch extends the
diagnostic to cover all of the relevant instructions.

Differential Revision: https://reviews.llvm.org/D30398

llvm-svn: 296459

1 files changed, 7 insertions, 4 deletions

diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 03e1d447b66..dae8618fa07 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -6305,10 +6305,6 @@ bool ARMAsmParser::validatetLDMRegList(const MCInst &Inst,
   else if (ListContainsPC && ListContainsLR)
     return Error(Operands[ListNo + HasWritebackToken]->getStartLoc(),
                  "PC and LR may not be in the register list simultaneously");
-  else if (inITBlock() && !lastInITBlock() && ListContainsPC)
-    return Error(Operands[ListNo + HasWritebackToken]->getStartLoc(),
-                 "instruction must be outside of IT block or the last "
-                 "instruction in an IT block");
   return false;
 }
 
@@ -6370,6 +6366,12 @@ bool ARMAsmParser::validateInstruction(MCInst &Inst,
     return Warning(Loc, "predicated instructions should be in IT block");
   }
 
+  // PC-setting instructions in an IT block, but not the last instruction of
+  // the block, are UNPREDICTABLE.
+  if (inExplicitITBlock() && !lastInITBlock() && isITBlockTerminator(Inst)) {
+    return Error(Loc, "instruction must be outside of IT block or the last instruction in an IT block");
+  }
+
   const unsigned Opcode = Inst.getOpcode();
   switch (Opcode) {
   case ARM::LDRD:
@@ -9013,6 +9015,7 @@ bool ARMAsmParser::isITBlockTerminator(MCInst &Inst) const {
   // operands. We only care about Thumb instructions here, as ARM instructions
   // obviously can't be in an IT block.
   switch (Inst.getOpcode()) {
+  case ARM::tLDMIA:
   case ARM::t2LDMIA:
   case ARM::t2LDMIA_UPD:
   case ARM::t2LDMDB: