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ARM: relax the atomic release barrier to "dmb ishst"

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I believe the full "dmb ish" barrier is not required to guarantee release
semantics for atomic operations. The weaker "dmb ishst" prevents previous
operations being reordered with a store executed afterwards, which is enough.

A key point to note (fortunately already correct) is that this barrier alone is
*insufficient* for sequential consistency, no matter how liberally placed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185339 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover 2013-07-01 14:48:48 +00:00
parent 728af3d574
commit d59fc0af0a
3 changed files with 95 additions and 57 deletions
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6
lib/Target/ARM/ARMISelLowering.cpp
View File

@ -2557,8 +2557,12 @@ static SDValue LowerATOMIC_FENCE(SDValue Op, SelectionDAG &DAG,
DAG.getConstant(0, MVT::i32));
}
ConstantSDNode *OrdN = cast<ConstantSDNode>(Op.getOperand(1));
AtomicOrdering Ord = static_cast<AtomicOrdering>(OrdN->getZExtValue());
unsigned Domain = Ord == Release ? ARM_MB::ISHST : ARM_MB::ISH;
return DAG.getNode(ARMISD::MEMBARRIER, dl, MVT::Other, Op.getOperand(0),
DAG.getConstant(ARM_MB::ISH, MVT::i32));
DAG.getConstant(Domain, MVT::i32));
}
static SDValue LowerPREFETCH(SDValue Op, SelectionDAG &DAG,

100
test/CodeGen/ARM/atomic-64bit.ll
View File

@ -3,24 +3,24 @@
define i64 @test1(i64* %ptr, i64 %val) {
; CHECK: test1:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: adds [[REG3:(r[0-9]?[02468])]], [[REG1]]
; CHECK: adc [[REG4:(r[0-9]?[13579])]], [[REG2]]
; CHECK: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test1:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: adds.w [[REG3:[a-z0-9]+]], [[REG1]]
; CHECK-THUMB: adc.w [[REG4:[a-z0-9]+]], [[REG2]]
; CHECK-THUMB: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw add i64* %ptr, i64 %val seq_cst
ret i64 %r
@ -28,24 +28,24 @@ define i64 @test1(i64* %ptr, i64 %val) {
define i64 @test2(i64* %ptr, i64 %val) {
; CHECK: test2:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: subs [[REG3:(r[0-9]?[02468])]], [[REG1]]
; CHECK: sbc [[REG4:(r[0-9]?[13579])]], [[REG2]]
; CHECK: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test2:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: subs.w [[REG3:[a-z0-9]+]], [[REG1]]
; CHECK-THUMB: sbc.w [[REG4:[a-z0-9]+]], [[REG2]]
; CHECK-THUMB: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw sub i64* %ptr, i64 %val seq_cst
ret i64 %r
@ -53,24 +53,24 @@ define i64 @test2(i64* %ptr, i64 %val) {
define i64 @test3(i64* %ptr, i64 %val) {
; CHECK: test3:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: and [[REG3:(r[0-9]?[02468])]], [[REG1]]
; CHECK: and [[REG4:(r[0-9]?[13579])]], [[REG2]]
; CHECK: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test3:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: and.w [[REG3:[a-z0-9]+]], [[REG1]]
; CHECK-THUMB: and.w [[REG4:[a-z0-9]+]], [[REG2]]
; CHECK-THUMB: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw and i64* %ptr, i64 %val seq_cst
ret i64 %r
@ -78,24 +78,24 @@ define i64 @test3(i64* %ptr, i64 %val) {
define i64 @test4(i64* %ptr, i64 %val) {
; CHECK: test4:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: orr [[REG3:(r[0-9]?[02468])]], [[REG1]]
; CHECK: orr [[REG4:(r[0-9]?[13579])]], [[REG2]]
; CHECK: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test4:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: orr.w [[REG3:[a-z0-9]+]], [[REG1]]
; CHECK-THUMB: orr.w [[REG4:[a-z0-9]+]], [[REG2]]
; CHECK-THUMB: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw or i64* %ptr, i64 %val seq_cst
ret i64 %r
@ -103,24 +103,24 @@ define i64 @test4(i64* %ptr, i64 %val) {
define i64 @test5(i64* %ptr, i64 %val) {
; CHECK: test5:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: eor [[REG3:(r[0-9]?[02468])]], [[REG1]]
; CHECK: eor [[REG4:(r[0-9]?[13579])]], [[REG2]]
; CHECK: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test5:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: eor.w [[REG3:[a-z0-9]+]], [[REG1]]
; CHECK-THUMB: eor.w [[REG4:[a-z0-9]+]], [[REG2]]
; CHECK-THUMB: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw xor i64* %ptr, i64 %val seq_cst
ret i64 %r
@ -128,20 +128,20 @@ define i64 @test5(i64* %ptr, i64 %val) {
define i64 @test6(i64* %ptr, i64 %val) {
; CHECK: test6:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: strexd {{[a-z0-9]+}}, {{r[0-9]?[02468]}}, {{r[0-9]?[13579]}}
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test6:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: strexd {{[a-z0-9]+}}, {{[a-z0-9]+}}, {{[a-z0-9]+}}
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw xchg i64* %ptr, i64 %val seq_cst
ret i64 %r
@ -149,7 +149,7 @@ define i64 @test6(i64* %ptr, i64 %val) {
define i64 @test7(i64* %ptr, i64 %val1, i64 %val2) {
; CHECK: test7:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: cmp [[REG1]]
; CHECK: cmpeq [[REG2]]
@ -157,10 +157,10 @@ define i64 @test7(i64* %ptr, i64 %val1, i64 %val2) {
; CHECK: strexd {{[a-z0-9]+}}, {{r[0-9]?[02468]}}, {{r[0-9]?[13579]}}
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test7:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: cmp [[REG1]]
; CHECK-THUMB: it eq
@ -169,7 +169,7 @@ define i64 @test7(i64* %ptr, i64 %val1, i64 %val2) {
; CHECK-THUMB: strexd {{[a-z0-9]+}}, {{[a-z0-9]+}}, {{[a-z0-9]+}}
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = cmpxchg i64* %ptr, i64 %val1, i64 %val2 seq_cst
ret i64 %r
@ -186,7 +186,7 @@ define i64 @test8(i64* %ptr) {
; CHECK: strexd {{[a-z0-9]+}}, {{r[0-9]?[02468]}}, {{r[0-9]?[13579]}}
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test8:
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
@ -197,7 +197,7 @@ define i64 @test8(i64* %ptr) {
; CHECK-THUMB: strexd {{[a-z0-9]+}}, {{[a-z0-9]+}}, {{[a-z0-9]+}}
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = load atomic i64* %ptr seq_cst, align 8
ret i64 %r
@ -207,20 +207,20 @@ define i64 @test8(i64* %ptr) {
; way to write it.
define void @test9(i64* %ptr, i64 %val) {
; CHECK: test9:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: strexd {{[a-z0-9]+}}, {{r[0-9]?[02468]}}, {{r[0-9]?[13579]}}
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test9:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: strexd {{[a-z0-9]+}}, {{[a-z0-9]+}}, {{[a-z0-9]+}}
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
store atomic i64 %val, i64* %ptr seq_cst, align 8
ret void
@ -228,7 +228,7 @@ define void @test9(i64* %ptr, i64 %val) {
define i64 @test10(i64* %ptr, i64 %val) {
; CHECK: test10:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: subs {{[a-z0-9]+}}, [[REG1]], [[REG3:(r[0-9]?[02468])]]
; CHECK: sbcs {{[a-z0-9]+}}, [[REG2]], [[REG4:(r[0-9]?[13579])]]
@ -236,10 +236,10 @@ define i64 @test10(i64* %ptr, i64 %val) {
; CHECK: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test10:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: subs.w {{[a-z0-9]+}}, [[REG1]], [[REG3:[a-z0-9]+]]
; CHECK-THUMB: sbcs.w {{[a-z0-9]+}}, [[REG2]], [[REG4:[a-z0-9]+]]
@ -247,7 +247,7 @@ define i64 @test10(i64* %ptr, i64 %val) {
; CHECK-THUMB: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw min i64* %ptr, i64 %val seq_cst
ret i64 %r
@ -255,7 +255,7 @@ define i64 @test10(i64* %ptr, i64 %val) {
define i64 @test11(i64* %ptr, i64 %val) {
; CHECK: test11:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: subs {{[a-z0-9]+}}, [[REG1]], [[REG3:(r[0-9]?[02468])]]
; CHECK: sbcs {{[a-z0-9]+}}, [[REG2]], [[REG4:(r[0-9]?[13579])]]
@ -263,11 +263,11 @@ define i64 @test11(i64* %ptr, i64 %val) {
; CHECK: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test11:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: subs.w {{[a-z0-9]+}}, [[REG1]], [[REG3:[a-z0-9]+]]
; CHECK-THUMB: sbcs.w {{[a-z0-9]+}}, [[REG2]], [[REG4:[a-z0-9]+]]
@ -275,7 +275,7 @@ define i64 @test11(i64* %ptr, i64 %val) {
; CHECK-THUMB: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw umin i64* %ptr, i64 %val seq_cst
ret i64 %r
@ -283,7 +283,7 @@ define i64 @test11(i64* %ptr, i64 %val) {
define i64 @test12(i64* %ptr, i64 %val) {
; CHECK: test12:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: subs {{[a-z0-9]+}}, [[REG1]], [[REG3:(r[0-9]?[02468])]]
; CHECK: sbcs {{[a-z0-9]+}}, [[REG2]], [[REG4:(r[0-9]?[13579])]]
@ -291,10 +291,10 @@ define i64 @test12(i64* %ptr, i64 %val) {
; CHECK: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test12:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: subs.w {{[a-z0-9]+}}, [[REG1]], [[REG3:[a-z0-9]+]]
; CHECK-THUMB: sbcs.w {{[a-z0-9]+}}, [[REG2]], [[REG4:[a-z0-9]+]]
@ -302,7 +302,7 @@ define i64 @test12(i64* %ptr, i64 %val) {
; CHECK-THUMB: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw max i64* %ptr, i64 %val seq_cst
ret i64 %r
@ -310,7 +310,7 @@ define i64 @test12(i64* %ptr, i64 %val) {
define i64 @test13(i64* %ptr, i64 %val) {
; CHECK: test13:
; CHECK: dmb ish
; CHECK: dmb ishst
; CHECK: ldrexd [[REG1:(r[0-9]?[02468])]], [[REG2:(r[0-9]?[13579])]]
; CHECK: subs {{[a-z0-9]+}}, [[REG1]], [[REG3:(r[0-9]?[02468])]]
; CHECK: sbcs {{[a-z0-9]+}}, [[REG2]], [[REG4:(r[0-9]?[13579])]]
@ -318,10 +318,10 @@ define i64 @test13(i64* %ptr, i64 %val) {
; CHECK: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK: cmp
; CHECK: bne
; CHECK: dmb ish
; CHECK: dmb {{ish$}}
; CHECK-THUMB: test13:
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb ishst
; CHECK-THUMB: ldrexd [[REG1:[a-z0-9]+]], [[REG2:[a-z0-9]+]]
; CHECK-THUMB: subs.w {{[a-z0-9]+}}, [[REG1]], [[REG3:[a-z0-9]+]]
; CHECK-THUMB: sbcs.w {{[a-z0-9]+}}, [[REG2]], [[REG4:[a-z0-9]+]]
@ -329,7 +329,7 @@ define i64 @test13(i64* %ptr, i64 %val) {
; CHECK-THUMB: strexd {{[a-z0-9]+}}, [[REG3]], [[REG4]]
; CHECK-THUMB: cmp
; CHECK-THUMB: bne
; CHECK-THUMB: dmb ish
; CHECK-THUMB: dmb {{ish$}}
%r = atomicrmw umax i64* %ptr, i64 %val seq_cst
ret i64 %r
}

46
test/CodeGen/ARM/atomic-load-store.ll
View File

@ -6,15 +6,15 @@
define void @test1(i32* %ptr, i32 %val1) {
; ARM: test1
; ARM: dmb ish
; ARM: dmb ishst
; ARM-NEXT: str
; ARM-NEXT: dmb ish
; ARM-NEXT: dmb {{ish$}}
; THUMBONE: test1
; THUMBONE: __sync_lock_test_and_set_4
; THUMBTWO: test1
; THUMBTWO: dmb ish
; THUMBTWO: dmb ishst
; THUMBTWO-NEXT: str
; THUMBTWO-NEXT: dmb ish
; THUMBTWO-NEXT: dmb {{ish$}}
store atomic i32 %val1, i32* %ptr seq_cst, align 4
ret void
}
@ -22,12 +22,12 @@ define void @test1(i32* %ptr, i32 %val1) {
define i32 @test2(i32* %ptr) {
; ARM: test2
; ARM: ldr
; ARM-NEXT: dmb ish
; ARM-NEXT: dmb {{ish$}}
; THUMBONE: test2
; THUMBONE: __sync_val_compare_and_swap_4
; THUMBTWO: test2
; THUMBTWO: ldr
; THUMBTWO-NEXT: dmb ish
; THUMBTWO-NEXT: dmb {{ish$}}
%val = load atomic i32* %ptr seq_cst, align 4
ret i32 %val
}
@ -69,3 +69,37 @@ define void @test_old_store_64bit(i64* %p, i64 %v) {
store atomic i64 %v, i64* %p seq_cst, align 8
ret void
}
; Release operations only need the store barrier provided by a "dmb ishst",
define void @test_store_release(i32* %p, i32 %v) {
; ARM: test_store_release:
; ARM: dmb ishst
; THUMBTWO: test_store_release:
; THUMBTWO: dmb ishst
store atomic i32 %v, i32* %p release, align 4
ret void
}
; However, if sequential consistency is needed *something* must ensure a release
; followed by an acquire does not get reordered. In that case a "dmb ishst" is
; not adequate.
define i32 @test_seq_cst(i32* %p, i32 %v) {
; ARM: test_seq_cst:
; ARM: dmb ishst
; ARM: str
; ARM: dmb {{ish$}}
; ARM: ldr
; ARM: dmb {{ish$}}
; THUMBTWO: test_seq_cst:
; THUMBTWO: dmb ishst
; THUMBTWO: str
; THUMBTWO: dmb {{ish$}}
; THUMBTWO: ldr
; THUMBTWO: dmb {{ish$}}
store atomic i32 %v, i32* %p seq_cst, align 4
%val = load atomic i32* %p seq_cst, align 4
ret i32 %val
}