ARM assemly parsing and validation of IT instruction.

"Although a Thumb2 instruction, the IT mnemonic shall be permitted in
ARM mode, and the condition verified to match the condition code(s)
on the following instruction(s)."

PR11853

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148969 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 25 insertions, 3 deletions

diff --git a/lib/Target/ARM/ARMInstrInfo.td b/lib/Target/ARM/ARMInstrInfo.td
index e319047..ce3e770 100644
--- a/lib/Target/ARM/ARMInstrInfo.td
+++ b/lib/Target/ARM/ARMInstrInfo.td
@@ -5179,3 +5179,7 @@ def : ARMInstAlias<"mul${s}${p} $Rn, $Rm",
 // "neg" is and alias for "rsb rd, rn, #0"
 def : ARMInstAlias<"neg${s}${p} $Rd, $Rm",
                    (RSBri GPR:$Rd, GPR:$Rm, 0, pred:$p, cc_out:$s)>;
+
+// 'it' blocks in ARM mode just validate the predicates. The IT itself
+// is discarded.
+def ITasm : ARMAsmPseudo<"it$mask $cc", (ins it_pred:$cc, it_mask:$mask)>;
diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 94604c9..ec9baf9 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -5080,10 +5080,11 @@ validateInstruction(MCInst &Inst,
   const MCInstrDesc &MCID = getInstDesc(Inst.getOpcode());
   SMLoc Loc = Operands[0]->getStartLoc();
   // Check the IT block state first.
-  // NOTE: In Thumb mode, the BKPT instruction has the interesting property of
-  // being allowed in IT blocks, but not being predicable.  It just always
+  // NOTE: BKPT instruction has the interesting property of being
+  // allowed in IT blocks, but not being predicable.  It just always
   // executes.
-  if (inITBlock() && Inst.getOpcode() != ARM::tBKPT) {
+  if (inITBlock() && Inst.getOpcode() != ARM::tBKPT &&
+      Inst.getOpcode() != ARM::BKPT) {
     unsigned bit = 1;
     if (ITState.FirstCond)
       ITState.FirstCond = false;
@@ -7048,6 +7049,7 @@ processInstruction(MCInst &Inst,
     }
     return false;
   }
+  case ARM::ITasm:
   case ARM::t2IT: {
     // The mask bits for all but the first condition are represented as
     // the low bit of the condition code value implies 't'. We currently
@@ -7154,6 +7156,11 @@ MatchAndEmitInstruction(SMLoc IDLoc,
     // block.
     forwardITPosition();
 
+    // ITasm is an ARM mode pseudo-instruction that just sets the ITblock and
+    // doesn't actually encode.
+    if (Inst.getOpcode() == ARM::ITasm)
+      return false;
+
     Out.EmitInstruction(Inst);
     return false;
   case Match_MissingFeature:
diff --git a/test/MC/ARM/arm-it-block.s b/test/MC/ARM/arm-it-block.s
new file mode 100644
index 0000000..e5e5491
--- /dev/null
+++ b/test/MC/ARM/arm-it-block.s
@@ -0,0 +1,11 @@
+@ RUN: llvm-mc -triple=armv7-apple-darwin -show-encoding < %s | FileCheck %s
+  .syntax unified
+  .globl _func
+
+_func:
+@ CHECK: _func:
+        it eq
+        moveq r2, r3
+@ 'it' is parsed but not encoded.
+@ CHECK-NOT: it
+@ CHECK: moveq	r2, r3          @ encoding: [0x03,0x20,0xa0,0x01]