[llvm] r193399 - ARM: don't expand atomicrmw inline on Cortex-M0

[Tim Northover]

Author: tnorthover
Date: Fri Oct 25 04:30:24 2013
New Revision: 193399

URL: http://llvm.org/viewvc/llvm-project?rev=193399&view=rev
Log:
ARM: don't expand atomicrmw inline on Cortex-M0

There's a barrier instruction so that should still be used, but most actual
atomic operations are going to need a platform decision on the correct
behaviour (either nop if single-threaded or OS-support otherwise).

rdar://problem/15287210

Modified:
    llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
    llvm/trunk/lib/Target/ARM/ARMSubtarget.h
    llvm/trunk/test/CodeGen/ARM/atomic-op.ll

Modified: llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp?rev=193399&r1=193398&r2=193399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp Fri Oct 25 04:30:24 2013
@@ -753,12 +753,10 @@ ARMTargetLowering::ARMTargetLowering(Tar
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i32, Expand);
   // ARMv6 Thumb1 (except for CPUs that support dmb / dsb) and earlier use
   // the default expansion.
-  // FIXME: This should be checking for v6k, not just v6.
-  if (Subtarget->hasDataBarrier() ||
-      (Subtarget->hasV6Ops() && !Subtarget->isThumb())) {
-    // membarrier needs custom lowering; the rest are legal and handled
-    // normally.
-    setOperationAction(ISD::ATOMIC_FENCE, MVT::Other, Custom);
+  if (Subtarget->hasAnyDataBarrier() && !Subtarget->isThumb1Only()) {
+    // ATOMIC_FENCE needs custom lowering; the other 32-bit ones are legal and
+    // handled normally.
+    setOperationAction(ISD::ATOMIC_FENCE,     MVT::Other, Custom);
     // Custom lowering for 64-bit ops
     setOperationAction(ISD::ATOMIC_LOAD_ADD,  MVT::i64, Custom);
     setOperationAction(ISD::ATOMIC_LOAD_SUB,  MVT::i64, Custom);
@@ -778,10 +776,13 @@ ARMTargetLowering::ARMTargetLowering(Tar
       setInsertFencesForAtomic(true);
     }
     setOperationAction(ISD::ATOMIC_LOAD, MVT::i64, Custom);
-    //setOperationAction(ISD::ATOMIC_STORE, MVT::i64, Custom);
   } else {
+    // If there's anything we can use as a barrier, go through custom lowering
+    // for ATOMIC_FENCE.
+    setOperationAction(ISD::ATOMIC_FENCE,   MVT::Other,
+                       Subtarget->hasAnyDataBarrier() ? Custom : Expand);
+
     // Set them all for expansion, which will force libcalls.
-    setOperationAction(ISD::ATOMIC_FENCE,   MVT::Other, Expand);
     setOperationAction(ISD::ATOMIC_CMP_SWAP,  MVT::i32, Expand);
     setOperationAction(ISD::ATOMIC_SWAP,      MVT::i32, Expand);
     setOperationAction(ISD::ATOMIC_LOAD_ADD,  MVT::i32, Expand);
@@ -2681,7 +2682,7 @@ static SDValue LowerATOMIC_FENCE(SDValue
     // Thumb1 and pre-v6 ARM mode use a libcall instead and should never get
     // here.
     assert(Subtarget->hasV6Ops() && !Subtarget->isThumb() &&
-           "Unexpected ISD::MEMBARRIER encountered. Should be libcall!");
+           "Unexpected ISD::ATOMIC_FENCE encountered. Should be libcall!");
     return DAG.getNode(ARMISD::MEMBARRIER_MCR, dl, MVT::Other, Op.getOperand(0),
                        DAG.getConstant(0, MVT::i32));
   }

Modified: llvm/trunk/lib/Target/ARM/ARMSubtarget.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMSubtarget.h?rev=193399&r1=193398&r2=193399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMSubtarget.h (original)
+++ llvm/trunk/lib/Target/ARM/ARMSubtarget.h Fri Oct 25 04:30:24 2013
@@ -263,6 +263,9 @@ public:
   bool hasDivideInARMMode() const { return HasHardwareDivideInARM; }
   bool hasT2ExtractPack() const { return HasT2ExtractPack; }
   bool hasDataBarrier() const { return HasDataBarrier; }
+  bool hasAnyDataBarrier() const {
+    return HasDataBarrier || (hasV6Ops() && !isThumb());
+  }
   bool useMulOps() const { return UseMulOps; }
   bool useFPVMLx() const { return !SlowFPVMLx; }
   bool hasVMLxForwarding() const { return HasVMLxForwarding; }

Modified: llvm/trunk/test/CodeGen/ARM/atomic-op.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/atomic-op.ll?rev=193399&r1=193398&r2=193399&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/atomic-op.ll (original)
+++ llvm/trunk/test/CodeGen/ARM/atomic-op.ll Fri Oct 25 04:30:24 2013
@@ -1,6 +1,7 @@
 ; RUN: llc < %s -mtriple=armv7-apple-ios -verify-machineinstrs | FileCheck %s
 ; RUN: llc < %s -mtriple=thumbv7-apple-ios -verify-machineinstrs | FileCheck %s
 ; RUN: llc < %s -mtriple=thumbv6-apple-ios -verify-machineinstrs | FileCheck %s --check-prefix=CHECK-T1
+; RUN: llc < %s -mtriple=thumbv6-apple-ios -verify-machineinstrs -mcpu=cortex-m0 | FileCheck %s --check-prefix=CHECK-T1
 
 define void @func(i32 %argc, i8** %argv) nounwind {
 entry: