ARM: allow cortex-m0 to use hint instructions

The hint instructions ("nop", "yield", etc) are mostly Thumb2-only, but have
been ported across to the v6M architecture. Fortunately, v6M seems to sit
nicely between v6 (thumb-1 only) and v6T2, so we can add a feature for it
fairly easily.

rdar://problem/15144406

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192097 91177308-0d34-0410-b5e6-96231b3b80d8

8 files changed, 59 insertions, 21 deletions

diff --git a/lib/Target/ARM/ARM.td b/lib/Target/ARM/ARM.td
index 21d1c5b181..d839ca9c9f 100644
--- a/lib/Target/ARM/ARM.td
+++ b/lib/Target/ARM/ARM.td
@@ -146,9 +146,12 @@ def HasV5TEOps  : SubtargetFeature<"v5te", "HasV5TEOps", "true",
 def HasV6Ops    : SubtargetFeature<"v6", "HasV6Ops", "true",
                                    "Support ARM v6 instructions",
                                    [HasV5TEOps]>;
+def HasV6MOps   : SubtargetFeature<"v6m", "HasV6MOps", "true",
+                                   "Support ARM v6M instructions",
+                                   [HasV6Ops]>;
 def HasV6T2Ops  : SubtargetFeature<"v6t2", "HasV6T2Ops", "true",
                                    "Support ARM v6t2 instructions",
-                                   [HasV6Ops, FeatureThumb2]>;
+                                   [HasV6MOps, FeatureThumb2]>;
 def HasV7Ops    : SubtargetFeature<"v7", "HasV7Ops", "true",
                                    "Support ARM v7 instructions",
                                    [HasV6T2Ops, FeaturePerfMon]>;
@@ -254,7 +257,7 @@ def : Processor<"mpcore",           ARMV6Itineraries, [HasV6Ops, FeatureVFP2,
                                                        FeatureHasSlowFPVMLx]>;
 
 // V6M Processors.
-def : Processor<"cortex-m0",        ARMV6Itineraries, [HasV6Ops, FeatureNoARM,
+def : Processor<"cortex-m0",        ARMV6Itineraries, [HasV6MOps, FeatureNoARM,
                                                        FeatureDB, FeatureMClass]>;
 
 // V6T2 Processors.
diff --git a/lib/Target/ARM/ARMInstrInfo.td b/lib/Target/ARM/ARMInstrInfo.td
index d92b47729b..bc39a1da35 100644
--- a/lib/Target/ARM/ARMInstrInfo.td
+++ b/lib/Target/ARM/ARMInstrInfo.td
@@ -193,6 +193,9 @@ def HasV5TE          : Predicate<"Subtarget->hasV5TEOps()">,
 def HasV6            : Predicate<"Subtarget->hasV6Ops()">,
                                  AssemblerPredicate<"HasV6Ops", "armv6">;
 def NoV6             : Predicate<"!Subtarget->hasV6Ops()">;
+def HasV6M           : Predicate<"Subtarget->hasV6MOps()">,
+                                 AssemblerPredicate<"HasV6MOps",
+                                                    "armv6m or armv6t2">;
 def HasV6T2          : Predicate<"Subtarget->hasV6T2Ops()">,
                                  AssemblerPredicate<"HasV6T2Ops", "armv6t2">;
 def NoV6T2           : Predicate<"!Subtarget->hasV6T2Ops()">;
diff --git a/lib/Target/ARM/ARMInstrThumb.td b/lib/Target/ARM/ARMInstrThumb.td
index 458254ee62..9712ed3274 100644
--- a/lib/Target/ARM/ARMInstrThumb.td
+++ b/lib/Target/ARM/ARMInstrThumb.td
@@ -271,23 +271,23 @@ class T1SystemEncoding<bits<8> opc>
 
 def tNOP : T1pI<(outs), (ins), NoItinerary, "nop", "", []>,
            T1SystemEncoding<0x00>, // A8.6.110
-        Requires<[IsThumb2]>;
+        Requires<[IsThumb, HasV6M]>;
 
 def tYIELD : T1pI<(outs), (ins), NoItinerary, "yield", "", []>,
            T1SystemEncoding<0x10>, // A8.6.410
-           Requires<[IsThumb2]>;
+           Requires<[IsThumb, HasV6M]>;
 
 def tWFE : T1pI<(outs), (ins), NoItinerary, "wfe", "", []>,
            T1SystemEncoding<0x20>, // A8.6.408
-           Requires<[IsThumb2]>;
+           Requires<[IsThumb, HasV6M]>;
 
 def tWFI : T1pI<(outs), (ins), NoItinerary, "wfi", "", []>,
            T1SystemEncoding<0x30>, // A8.6.409
-           Requires<[IsThumb2]>;
+           Requires<[IsThumb, HasV6M]>;
 
 def tSEV : T1pI<(outs), (ins), NoItinerary, "sev", "", []>,
            T1SystemEncoding<0x40>, // A8.6.157
-           Requires<[IsThumb2]>;
+           Requires<[IsThumb, HasV6M]>;
 
 def tSEVL : T1pI<(outs), (ins), NoItinerary, "sevl", "", [(int_arm_sevl)]>,
             T1SystemEncoding<0x50>,
diff --git a/lib/Target/ARM/ARMSubtarget.h b/lib/Target/ARM/ARMSubtarget.h
index 11d8e8e6d6..7c7e402036 100644
--- a/lib/Target/ARM/ARMSubtarget.h
+++ b/lib/Target/ARM/ARMSubtarget.h
@@ -44,12 +44,13 @@ protected:
   ARMProcClassEnum ARMProcClass;
 
   /// HasV4TOps, HasV5TOps, HasV5TEOps,
-  /// HasV6Ops, HasV6T2Ops, HasV7Ops, HasV8Ops -
+  /// HasV6Ops, HasV6MOps, HasV6T2Ops, HasV7Ops, HasV8Ops -
   /// Specify whether target support specific ARM ISA variants.
   bool HasV4TOps;
   bool HasV5TOps;
   bool HasV5TEOps;
   bool HasV6Ops;
+  bool HasV6MOps;
   bool HasV6T2Ops;
   bool HasV7Ops;
   bool HasV8Ops;
diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index f482912d27..1e090d97da 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -162,6 +162,9 @@ class ARMAsmParser : public MCTargetAsmParser {
   bool hasV6Ops() const {
     return STI.getFeatureBits() & ARM::HasV6Ops;
   }
+  bool hasV6MOps() const {
+    return STI.getFeatureBits() & ARM::HasV6MOps;
+  }
   bool hasV7Ops() const {
     return STI.getFeatureBits() & ARM::HasV7Ops;
   }
@@ -4812,7 +4815,10 @@ getMnemonicAcceptInfo(StringRef Mnemonic, StringRef FullInst,
         Mnemonic != "stc2" && Mnemonic != "stc2l" &&
         !Mnemonic.startswith("rfe") && !Mnemonic.startswith("srs");
   } else if (isThumbOne()) {
-    CanAcceptPredicationCode = Mnemonic != "nop" && Mnemonic != "movs";
+    if (hasV6MOps())
+      CanAcceptPredicationCode = Mnemonic != "movs";
+    else
+      CanAcceptPredicationCode = Mnemonic != "nop" && Mnemonic != "movs";
   } else
     CanAcceptPredicationCode = true;
 }
diff --git a/test/MC/ARM/thumb-diagnostics.s b/test/MC/ARM/thumb-diagnostics.s
index 8f86323e25..a82d497cea 100644
--- a/test/MC/ARM/thumb-diagnostics.s
+++ b/test/MC/ARM/thumb-diagnostics.s
@@ -179,13 +179,13 @@ error: invalid operand for instruction
         wfi
         yield
 
-@ CHECK-ERRORS: error: instruction requires: thumb2
+@ CHECK-ERRORS: error: instruction requires: armv6m or armv6t2
 @ CHECK-ERRORS: wfe
 @ CHECK-ERRORS: ^
-@ CHECK-ERRORS: error: instruction requires: thumb2
+@ CHECK-ERRORS: error: instruction requires: armv6m or armv6t2
 @ CHECK-ERRORS: wfi
 @ CHECK-ERRORS: ^
-@ CHECK-ERRORS: error: instruction requires: thumb2
+@ CHECK-ERRORS: error: instruction requires: armv6m or armv6t2
 @ CHECK-ERRORS: yield
 @ CHECK-ERRORS: ^
 
diff --git a/test/MC/ARM/thumb-hints.s b/test/MC/ARM/thumb-hints.s
new file mode 100644
index 0000000000..73e83621a9
--- /dev/null
+++ b/test/MC/ARM/thumb-hints.s
@@ -0,0 +1,34 @@
+@ RUN: llvm-mc -triple=thumbv7-apple-darwin -show-encoding < %s | FileCheck %s
+@ RUN: llvm-mc -triple=thumbv6-apple-darwin -mcpu=cortex-m0 -show-encoding < %s | FileCheck %s 
+@ RUN: not llvm-mc -triple=thumbv6-apple-darwin -show-encoding < %s > %t 2> %t2
+@ RUN: FileCheck %s --check-prefix=CHECK-EVIL-PRE-UAL < %t
+@ RUN: FileCheck %s --check-prefix CHECK-ERROR < %t2
+
+  .syntax unified
+
+        nop
+        yield
+        wfe
+        wfi
+        sev
+@ CHECK: nop                            @ encoding: [0x00,0xbf]
+@ CHECK: yield                          @ encoding: [0x10,0xbf]
+@ CHECK: wfe                            @ encoding: [0x20,0xbf]
+@ CHECK: wfi                            @ encoding: [0x30,0xbf]
+@ CHECK: sev                            @ encoding: [0x40,0xbf]
+
+
+@ CHECK-EVIL-PRE-UAL: mov r8, r8                     @ encoding: [0xc0,0x46]
+
+
+@ CHECK-ERROR: error: instruction requires: armv6m or armv6t2
+@ CHECK-ERROR-NEXT: yield
+
+@ CHECK-ERROR: error: instruction requires: armv6m or armv6t2
+@ CHECK-ERROR-NEXT: wfe
+
+@ CHECK-ERROR: error: instruction requires: armv6m or armv6t2
+@ CHECK-ERROR-NEXT: wfi
+
+@ CHECK-ERROR: error: instruction requires: armv6m or armv6t2
+@ CHECK-ERROR-NEXT: sev
diff --git a/test/MC/ARM/thumb-nop.s b/test/MC/ARM/thumb-nop.s
deleted file mode 100644
index 66f61a6e0b..0000000000
--- a/test/MC/ARM/thumb-nop.s
+++ /dev/null
@@ -1,9 +0,0 @@
-@ RUN: llvm-mc -triple=thumbv6-apple-darwin -show-encoding < %s | FileCheck %s -check-prefix=CHECK-V6
-@ RUN: llvm-mc -triple=thumbv7-apple-darwin -show-encoding < %s | FileCheck %s -check-prefix=CHECK-V7
-
-  .syntax unified
-
-        nop
-
-@ CHECK-V6: mov r8, r8                     @ encoding: [0xc0,0x46]
-@ CHECK-V7: nop                            @ encoding: [0x00,0xbf]