[Cortex-M0] Atomic lowering

Summary: ARMv6m supports dmb etc fench instructions but not ldrex/strex etc. So for some atomic load/store, LLVM should inline instructions instead of lowering to __sync_ calls.

Reviewers: rengolin, efriedma, t.p.northover, jmolloy

Subscribers: efriedma, aemerson, llvm-commits

Differential Revision: https://reviews.llvm.org/D26120

llvm-svn: 285969

lib/Target/ARM/ARMISelLowering.cpp

@@ -1057,6 +1057,10 @@ ARMTargetLowering::ARMTargetLowering(const TargetMachine &TM,
   } else {
     // If there's anything we can use as a barrier, go through custom lowering
     // for ATOMIC_FENCE.
+    // If target has DMB in thumb, Fences can be inserted.
+    if (Subtarget->hasDataBarrier())
+      InsertFencesForAtomic = true;
+
     setOperationAction(ISD::ATOMIC_FENCE,   MVT::Other,
                        Subtarget->hasAnyDataBarrier() ? Custom : Expand);
 
@@ -1075,8 +1079,10 @@ ARMTargetLowering::ARMTargetLowering(const TargetMachine &TM,
     setOperationAction(ISD::ATOMIC_LOAD_UMAX, MVT::i32, Expand);
     // Mark ATOMIC_LOAD and ATOMIC_STORE custom so we can handle the
     // Unordered/Monotonic case.
-    setOperationAction(ISD::ATOMIC_LOAD, MVT::i32, Custom);
+    if (!InsertFencesForAtomic) {
-    setOperationAction(ISD::ATOMIC_STORE, MVT::i32, Custom);
+      setOperationAction(ISD::ATOMIC_LOAD, MVT::i32, Custom);
+      setOperationAction(ISD::ATOMIC_STORE, MVT::i32, Custom);
+    }
   }
 
   setOperationAction(ISD::PREFETCH,         MVT::Other, Custom);
@@ -12879,7 +12885,8 @@ ARMTargetLowering::shouldExpandAtomicLoadInIR(LoadInst *LI) const {
 TargetLowering::AtomicExpansionKind
 ARMTargetLowering::shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const {
   unsigned Size = AI->getType()->getPrimitiveSizeInBits();
-  return (Size <= (Subtarget->isMClass() ? 32U : 64U))
+  bool hasAtomicRMW = !Subtarget->isThumb() || Subtarget->hasV8MBaselineOps();
+  return (Size <= (Subtarget->isMClass() ? 32U : 64U) && hasAtomicRMW)
              ? AtomicExpansionKind::LLSC
              : AtomicExpansionKind::None;
 }
@@ -12891,7 +12898,9 @@ bool ARMTargetLowering::shouldExpandAtomicCmpXchgInIR(
   // on the stack and close enough to the spill slot, this can lead to a
   // situation where the monitor always gets cleared and the atomic operation
   // can never succeed. So at -O0 we need a late-expanded pseudo-inst instead.
-  return getTargetMachine().getOptLevel() != 0;
+  bool hasAtomicCmpXchg =
+      !Subtarget->isThumb() || Subtarget->hasV8MBaselineOps();
+  return getTargetMachine().getOptLevel() != 0 && hasAtomicCmpXchg;
 }
 
 bool ARMTargetLowering::shouldInsertFencesForAtomic(

lib/Target/ARM/ARMSubtarget.cpp

@@ -319,9 +319,7 @@ bool ARMSubtarget::enablePostRAScheduler() const {
   return (!isThumb() || hasThumb2());
 }
 
-bool ARMSubtarget::enableAtomicExpand() const {
+bool ARMSubtarget::enableAtomicExpand() const { return hasAnyDataBarrier(); }
-  return hasAnyDataBarrier() && (!isThumb() || hasV8MBaselineOps());
-}
 
 bool ARMSubtarget::useStride4VFPs(const MachineFunction &MF) const {
   // For general targets, the prologue can grow when VFPs are allocated with

test/CodeGen/ARM/atomic-op.ll

@@ -1,7 +1,7 @@
 ; RUN: llc < %s -mtriple=armv7-apple-ios -verify-machineinstrs | FileCheck %s --check-prefix=CHECK --check-prefix CHECK-ARMV7
 ; RUN: llc < %s -mtriple=thumbv7-apple-ios -verify-machineinstrs | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-T2
 ; 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
+; RUN: llc < %s -mtriple=thumbv6-apple-ios -verify-machineinstrs -mcpu=cortex-m0 | FileCheck %s --check-prefix=CHECK-T1-M0
 ; RUN: llc < %s -mtriple=thumbv7--none-eabi -thread-model single -verify-machineinstrs | FileCheck %s --check-prefix=CHECK-BAREMETAL
 
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
@@ -30,6 +30,7 @@ entry:
   ; CHECK: add
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_add_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_add_4
   ; CHECK-BAREMETAL: add
   ; CHECK-BAREMETAL-NOT: __sync
   %0 = atomicrmw add i32* %val1, i32 %tmp monotonic
@@ -38,6 +39,7 @@ entry:
   ; CHECK: sub
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_sub_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_sub_4
   ; CHECK-BAREMETAL: sub
   ; CHECK-BAREMETAL-NOT: __sync
   %1 = atomicrmw sub i32* %val2, i32 30 monotonic
@@ -46,6 +48,7 @@ entry:
   ; CHECK: add
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_add_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_add_4
   ; CHECK-BAREMETAL: add
   ; CHECK-BAREMETAL-NOT: __sync
   %2 = atomicrmw add i32* %val2, i32 1 monotonic
@@ -54,6 +57,7 @@ entry:
   ; CHECK: sub
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_sub_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_sub_4
   ; CHECK-BAREMETAL: sub
   ; CHECK-BAREMETAL-NOT: __sync
   %3 = atomicrmw sub i32* %val2, i32 1 monotonic
@@ -62,6 +66,7 @@ entry:
   ; CHECK: and
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_and_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_and_4
   ; CHECK-BAREMETAL: and
   ; CHECK-BAREMETAL-NOT: __sync
   %4 = atomicrmw and i32* %andt, i32 4080 monotonic
@@ -70,6 +75,7 @@ entry:
   ; CHECK: or
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_or_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_or_4
   ; CHECK-BAREMETAL: or
   ; CHECK-BAREMETAL-NOT: __sync
   %5 = atomicrmw or i32* %ort, i32 4080 monotonic
@@ -78,6 +84,7 @@ entry:
   ; CHECK: eor
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_xor_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_xor_4
   ; CHECK-BAREMETAL: eor
   ; CHECK-BAREMETAL-NOT: __sync
   %6 = atomicrmw xor i32* %xort, i32 4080 monotonic
@@ -86,6 +93,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_min_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_min_4
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %7 = atomicrmw min i32* %val2, i32 16 monotonic
@@ -95,6 +103,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_min_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_min_4
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %8 = atomicrmw min i32* %val2, i32 %neg monotonic
@@ -103,6 +112,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_max_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_max_4
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %9 = atomicrmw max i32* %val2, i32 1 monotonic
@@ -111,6 +121,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_max_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_max_4
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %10 = atomicrmw max i32* %val2, i32 0 monotonic
@@ -119,6 +130,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umin_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umin_4
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %11 = atomicrmw umin i32* %val2, i32 16 monotonic
@@ -128,6 +140,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umin_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umin_4
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %12 = atomicrmw umin i32* %val2, i32 %uneg monotonic
@@ -136,6 +149,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umax_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umax_4
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %13 = atomicrmw umax i32* %val2, i32 1 monotonic
@@ -144,6 +158,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umax_4
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umax_4
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %14 = atomicrmw umax i32* %val2, i32 0 monotonic
@@ -161,6 +176,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umin_2
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umin_2
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %0 = atomicrmw umin i16* %val, i16 16 monotonic
@@ -170,6 +186,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umin_2
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umin_2
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %1 = atomicrmw umin i16* %val, i16 %uneg monotonic
@@ -178,6 +195,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umax_2
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umax_2
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %2 = atomicrmw umax i16* %val, i16 1 monotonic
@@ -186,6 +204,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umax_2
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umax_2
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %3 = atomicrmw umax i16* %val, i16 0 monotonic
@@ -202,6 +221,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umin_1
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umin_1
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %0 = atomicrmw umin i8* %val, i8 16 monotonic
@@ -210,6 +230,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umin_1
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umin_1
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %uneg = sub i8 0, 1
@@ -219,6 +240,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umax_1
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umax_1
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %2 = atomicrmw umax i8* %val, i8 1 monotonic
@@ -227,6 +249,7 @@ entry:
   ; CHECK: cmp
   ; CHECK: strex
   ; CHECK-T1: bl ___sync_fetch_and_umax_1
+  ; CHECK-T1-M0: bl ___sync_fetch_and_umax_1
   ; CHECK-BAREMETAL: cmp
   ; CHECK-BAREMETAL-NOT: __sync
   %3 = atomicrmw umax i8* %val, i8 0 monotonic
@@ -319,6 +342,11 @@ define i32 @load_load_add_acquire(i32* %mem1, i32* %mem2) nounwind {
 ; CHECK: dmb
 ; CHECK: add r0,
 
+; CHECK-T1-M0: ldr {{r[0-9]}}, [r0]
+; CHECK-T1-M0: dmb
+; CHECK-T1-M0: ldr {{r[0-9]}}, [r1]
+; CHECK-T1-M0: dmb
+
 ; CHECK-T1: ___sync_val_compare_and_swap_4
 ; CHECK-T1: ___sync_val_compare_and_swap_4
 
@@ -344,6 +372,11 @@ define void @store_store_release(i32* %mem1, i32 %val1, i32* %mem2, i32 %val2) {
 ; CHECK-T1: ___sync_lock_test_and_set
 ; CHECK-T1: ___sync_lock_test_and_set
 
+; CHECK-T1-M0: dmb
+; CHECK-T1-M0: str r1, [r0]
+; CHECK-T1-M0: dmb
+; CHECK-T1-M0: str r3, [r2]
+
 ; CHECK-BAREMETAL-NOT: dmb
 ; CHECK-BAREMTEAL: str r1, [r0]
 ; CHECK-BAREMETAL-NOT: dmb
@@ -362,6 +395,10 @@ define void @load_fence_store_monotonic(i32* %mem1, i32* %mem2) {
 ; CHECK: dmb
 ; CHECK: str [[R0]], [r1]
 
+; CHECK-T1-M0: ldr [[R0:r[0-9]]], [r0]
+; CHECK-T1-M0: dmb
+; CHECK-T1-M0: str [[R0]], [r1]
+
 ; CHECK-T1: ldr [[R0:r[0-9]]], [{{r[0-9]+}}]
 ; CHECK-T1: {{dmb|bl ___sync_synchronize}}
 ; CHECK-T1: str [[R0]], [{{r[0-9]+}}]