diff --git a/llvm/lib/Target/Sparc/SparcISelLowering.cpp b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
index bdefb0841a124..13184a1eb0b10 100644
--- a/llvm/lib/Target/Sparc/SparcISelLowering.cpp
+++ b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
@@ -1764,9 +1764,14 @@ SparcTargetLowering::SparcTargetLowering(const TargetMachine &TM,
   // Atomics are supported on SparcV9. 32-bit atomics are also
   // supported by some Leon SparcV8 variants. Otherwise, atomics
   // are unsupported.
-  if (Subtarget->isV9())
-    setMaxAtomicSizeInBitsSupported(64);
-  else if (Subtarget->hasLeonCasa())
+  if (Subtarget->isV9()) {
+    // TODO: we _ought_ to be able to support 64-bit atomics on 32-bit sparcv9,
+    // but it hasn't been implemented in the backend yet.
+    if (Subtarget->is64Bit())
+      setMaxAtomicSizeInBitsSupported(64);
+    else
+      setMaxAtomicSizeInBitsSupported(32);
+  } else if (Subtarget->hasLeonCasa())
     setMaxAtomicSizeInBitsSupported(32);
   else
     setMaxAtomicSizeInBitsSupported(0);
diff --git a/llvm/test/CodeGen/SPARC/64atomics.ll b/llvm/test/CodeGen/SPARC/64atomics.ll
index 89175b6242e63..b11c0498fbbb4 100644
--- a/llvm/test/CodeGen/SPARC/64atomics.ll
+++ b/llvm/test/CodeGen/SPARC/64atomics.ll
@@ -1,12 +1,14 @@
-; RUN: llc < %s -march=sparcv9 -verify-machineinstrs | FileCheck %s
+; RUN: llc < %s -march=sparc -mcpu=v9 -verify-machineinstrs | FileCheck %s --check-prefixes=SPARC,SPARC32
+; RUN: llc < %s -march=sparcv9 -verify-machineinstrs | FileCheck %s --check-prefixes=SPARC,SPARC64
 
-; CHECK-LABEL: test_atomic_i64
-; CHECK:       ldx [%o0]
-; CHECK:       membar
-; CHECK:       ldx [%o1]
-; CHECK:       membar
-; CHECK:       membar
-; CHECK:       stx {{.+}}, [%o2]
+; SPARC-LABEL: test_atomic_i64
+; SPARC32:       __atomic_load_8
+; SPARC64:       ldx [%o0]
+; SPARC64:       membar
+; SPARC64:       ldx [%o1]
+; SPARC64:       membar
+; SPARC64:       membar
+; SPARC64:       stx {{.+}}, [%o2]
 define i64 @test_atomic_i64(i64* %ptr1, i64* %ptr2, i64* %ptr3) {
 entry:
   %0 = load atomic i64, i64* %ptr1 acquire, align 8
@@ -16,9 +18,10 @@ entry:
   ret i64 %2
 }
 
-; CHECK-LABEL: test_cmpxchg_i64
-; CHECK:       mov 123, [[R:%[gilo][0-7]]]
-; CHECK:       casx [%o1], %o0, [[R]]
+; SPARC-LABEL: test_cmpxchg_i64
+; SPARC32:       __atomic_compare_exchange_8
+; SPARC64:       mov 123, [[R:%[gilo][0-7]]]
+; SPARC64:       casx [%o1], %o0, [[R]]
 
 define i64 @test_cmpxchg_i64(i64 %a, i64* %ptr) {
 entry:
@@ -27,8 +30,9 @@ entry:
   ret i64 %b
 }
 
-; CHECK-LABEL: test_swap_i64
-; CHECK:       casx [%o1],
+; SPARC-LABEL: test_swap_i64
+; SPARC32:       __atomic_exchange_8
+; SPARC64:       casx [%o1],
 
 define i64 @test_swap_i64(i64 %a, i64* %ptr) {
 entry:
@@ -36,23 +40,25 @@ entry:
   ret i64 %b
 }
 
-; CHECK-LABEL: test_load_sub_64
-; CHECK: membar
-; CHECK: sub
-; CHECK: casx [%o0]
-; CHECK: membar
+; SPARC-LABEL: test_load_sub_64
+; SPARC32: __atomic_fetch_sub_8
+; SPARC64: membar
+; SPARC64: sub
+; SPARC64: casx [%o0]
+; SPARC64: membar
 define zeroext i64 @test_load_sub_64(i64* %p, i64 zeroext %v) {
 entry:
   %0 = atomicrmw sub i64* %p, i64 %v seq_cst
   ret i64 %0
 }
 
-; CHECK-LABEL: test_load_max_64
-; CHECK: membar
-; CHECK: cmp
-; CHECK: movg %xcc
-; CHECK: casx [%o0]
-; CHECK: membar
+; SPARC-LABEL: test_load_max_64
+; SPARC32: __atomic_compare_exchange_8
+; SPARC64: membar
+; SPARC64: cmp
+; SPARC64: movg %xcc
+; SPARC64: casx [%o0]
+; SPARC64: membar
 define zeroext i64 @test_load_max_64(i64* %p, i64 zeroext %v) {
 entry:
   %0 = atomicrmw max i64* %p, i64 %v seq_cst
diff --git a/llvm/test/CodeGen/SPARC/atomicrmw-uinc-udec-wrap.ll b/llvm/test/CodeGen/SPARC/atomicrmw-uinc-udec-wrap.ll
index 9b49035c46040..0f9feeb17716a 100644
--- a/llvm/test/CodeGen/SPARC/atomicrmw-uinc-udec-wrap.ll
+++ b/llvm/test/CodeGen/SPARC/atomicrmw-uinc-udec-wrap.ll
@@ -117,43 +117,41 @@ define i64 @atomicrmw_uinc_wrap_i64(ptr %ptr, i64 %val) {
 ; CHECK-LABEL: atomicrmw_uinc_wrap_i64:
 ; CHECK:         .cfi_startproc
 ; CHECK-NEXT:  ! %bb.0:
-; CHECK-NEXT:    save %sp, -96, %sp
+; CHECK-NEXT:    save %sp, -104, %sp
 ; CHECK-NEXT:    .cfi_def_cfa_register %fp
 ; CHECK-NEXT:    .cfi_window_save
 ; CHECK-NEXT:    .cfi_register %o7, %i7
-; CHECK-NEXT:    membar #LoadLoad | #StoreLoad | #LoadStore | #StoreStore
-; CHECK-NEXT:    ldd [%i0], %i4
+; CHECK-NEXT:    ldd [%i0], %g2
+; CHECK-NEXT:    add %fp, -8, %i3
+; CHECK-NEXT:    mov 5, %i4
 ; CHECK-NEXT:  .LBB3_1: ! %atomicrmw.start
 ; CHECK-NEXT:    ! =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    mov %g0, %i3
-; CHECK-NEXT:    mov %g0, %g2
-; CHECK-NEXT:    addcc %i5, 1, %o4
-; CHECK-NEXT:    addxcc %i4, 0, %o3
-; CHECK-NEXT:    cmp %i4, %i1
-; CHECK-NEXT:    movcc %icc, 1, %i3
-; CHECK-NEXT:    cmp %i5, %i2
-; CHECK-NEXT:    movcc %icc, 1, %g2
-; CHECK-NEXT:    cmp %i4, %i1
-; CHECK-NEXT:    move %icc, %g2, %i3
-; CHECK-NEXT:    cmp %i3, 0
+; CHECK-NEXT:    mov %g0, %i5
+; CHECK-NEXT:    mov %g0, %g4
+; CHECK-NEXT:    addcc %g3, 1, %o3
+; CHECK-NEXT:    addxcc %g2, 0, %o2
+; CHECK-NEXT:    cmp %g2, %i1
+; CHECK-NEXT:    movcc %icc, 1, %i5
+; CHECK-NEXT:    cmp %g3, %i2
+; CHECK-NEXT:    movcc %icc, 1, %g4
+; CHECK-NEXT:    cmp %g2, %i1
+; CHECK-NEXT:    move %icc, %g4, %i5
+; CHECK-NEXT:    cmp %i5, 0
+; CHECK-NEXT:    movne %icc, 0, %o2
 ; CHECK-NEXT:    movne %icc, 0, %o3
-; CHECK-NEXT:    movne %icc, 0, %o4
+; CHECK-NEXT:    std %g2, [%fp+-8]
 ; CHECK-NEXT:    mov %i0, %o0
-; CHECK-NEXT:    mov %i4, %o1
-; CHECK-NEXT:    call __sync_val_compare_and_swap_8
-; CHECK-NEXT:    mov %i5, %o2
-; CHECK-NEXT:    xor %o0, %i4, %i3
-; CHECK-NEXT:    xor %o1, %i5, %i4
-; CHECK-NEXT:    or %i4, %i3, %i3
-; CHECK-NEXT:    mov %o1, %i5
-; CHECK-NEXT:    cmp %i3, 0
-; CHECK-NEXT:    bne %icc, .LBB3_1
-; CHECK-NEXT:    mov %o0, %i4
+; CHECK-NEXT:    mov %i3, %o1
+; CHECK-NEXT:    mov %i4, %o4
+; CHECK-NEXT:    call __atomic_compare_exchange_8
+; CHECK-NEXT:    mov %i4, %o5
+; CHECK-NEXT:    cmp %o0, 0
+; CHECK-NEXT:    be %icc, .LBB3_1
+; CHECK-NEXT:    ldd [%fp+-8], %g2
 ; CHECK-NEXT:  ! %bb.2: ! %atomicrmw.end
-; CHECK-NEXT:    membar #LoadLoad | #StoreLoad | #LoadStore | #StoreStore
-; CHECK-NEXT:    mov %i4, %i0
+; CHECK-NEXT:    mov %g2, %i0
 ; CHECK-NEXT:    ret
-; CHECK-NEXT:    restore %g0, %i5, %o1
+; CHECK-NEXT:    restore %g0, %g3, %o1
   %result = atomicrmw uinc_wrap ptr %ptr, i64 %val seq_cst
   ret i64 %result
 }
@@ -280,48 +278,46 @@ define i64 @atomicrmw_udec_wrap_i64(ptr %ptr, i64 %val) {
 ; CHECK-LABEL: atomicrmw_udec_wrap_i64:
 ; CHECK:         .cfi_startproc
 ; CHECK-NEXT:  ! %bb.0:
-; CHECK-NEXT:    save %sp, -96, %sp
+; CHECK-NEXT:    save %sp, -104, %sp
 ; CHECK-NEXT:    .cfi_def_cfa_register %fp
 ; CHECK-NEXT:    .cfi_window_save
 ; CHECK-NEXT:    .cfi_register %o7, %i7
-; CHECK-NEXT:    membar #LoadLoad | #StoreLoad | #LoadStore | #StoreStore
-; CHECK-NEXT:    ldd [%i0], %i4
+; CHECK-NEXT:    ldd [%i0], %g2
+; CHECK-NEXT:    add %fp, -8, %i3
+; CHECK-NEXT:    mov 5, %i4
 ; CHECK-NEXT:  .LBB7_1: ! %atomicrmw.start
 ; CHECK-NEXT:    ! =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    mov %g0, %i3
-; CHECK-NEXT:    mov %g0, %g2
-; CHECK-NEXT:    mov %g0, %g3
-; CHECK-NEXT:    addcc %i5, -1, %o4
-; CHECK-NEXT:    addxcc %i4, -1, %o3
-; CHECK-NEXT:    or %i5, %i4, %g4
-; CHECK-NEXT:    cmp %g4, 0
-; CHECK-NEXT:    move %icc, 1, %i3
-; CHECK-NEXT:    cmp %i4, %i1
-; CHECK-NEXT:    movgu %icc, 1, %g2
-; CHECK-NEXT:    cmp %i5, %i2
-; CHECK-NEXT:    movgu %icc, 1, %g3
-; CHECK-NEXT:    cmp %i4, %i1
-; CHECK-NEXT:    move %icc, %g3, %g2
-; CHECK-NEXT:    or %i3, %g2, %i3
-; CHECK-NEXT:    cmp %i3, 0
-; CHECK-NEXT:    movne %icc, %i1, %o3
-; CHECK-NEXT:    movne %icc, %i2, %o4
+; CHECK-NEXT:    mov %g0, %i5
+; CHECK-NEXT:    mov %g0, %g4
+; CHECK-NEXT:    mov %g0, %l0
+; CHECK-NEXT:    addcc %g3, -1, %o3
+; CHECK-NEXT:    addxcc %g2, -1, %o2
+; CHECK-NEXT:    or %g3, %g2, %l1
+; CHECK-NEXT:    cmp %l1, 0
+; CHECK-NEXT:    move %icc, 1, %i5
+; CHECK-NEXT:    cmp %g2, %i1
+; CHECK-NEXT:    movgu %icc, 1, %g4
+; CHECK-NEXT:    cmp %g3, %i2
+; CHECK-NEXT:    movgu %icc, 1, %l0
+; CHECK-NEXT:    cmp %g2, %i1
+; CHECK-NEXT:    move %icc, %l0, %g4
+; CHECK-NEXT:    or %i5, %g4, %i5
+; CHECK-NEXT:    cmp %i5, 0
+; CHECK-NEXT:    movne %icc, %i1, %o2
+; CHECK-NEXT:    movne %icc, %i2, %o3
+; CHECK-NEXT:    std %g2, [%fp+-8]
 ; CHECK-NEXT:    mov %i0, %o0
-; CHECK-NEXT:    mov %i4, %o1
-; CHECK-NEXT:    call __sync_val_compare_and_swap_8
-; CHECK-NEXT:    mov %i5, %o2
-; CHECK-NEXT:    xor %o0, %i4, %i3
-; CHECK-NEXT:    xor %o1, %i5, %i4
-; CHECK-NEXT:    or %i4, %i3, %i3
-; CHECK-NEXT:    mov %o1, %i5
-; CHECK-NEXT:    cmp %i3, 0
-; CHECK-NEXT:    bne %icc, .LBB7_1
-; CHECK-NEXT:    mov %o0, %i4
+; CHECK-NEXT:    mov %i3, %o1
+; CHECK-NEXT:    mov %i4, %o4
+; CHECK-NEXT:    call __atomic_compare_exchange_8
+; CHECK-NEXT:    mov %i4, %o5
+; CHECK-NEXT:    cmp %o0, 0
+; CHECK-NEXT:    be %icc, .LBB7_1
+; CHECK-NEXT:    ldd [%fp+-8], %g2
 ; CHECK-NEXT:  ! %bb.2: ! %atomicrmw.end
-; CHECK-NEXT:    membar #LoadLoad | #StoreLoad | #LoadStore | #StoreStore
-; CHECK-NEXT:    mov %i4, %i0
+; CHECK-NEXT:    mov %g2, %i0
 ; CHECK-NEXT:    ret
-; CHECK-NEXT:    restore %g0, %i5, %o1
+; CHECK-NEXT:    restore %g0, %g3, %o1
   %result = atomicrmw udec_wrap ptr %ptr, i64 %val seq_cst
   ret i64 %result
 }