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66b380b6b6
Even loads/stores that have a stronger ordering than monotonic can be safe. The rule is no release-acquire pair on the path from the QueryInst, assuming that the QueryInst is not atomic itself. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216771 91177308-0d34-0410-b5e6-96231b3b80d8
179 lines
4.6 KiB
LLVM
179 lines
4.6 KiB
LLVM
; RUN: opt -basicaa -dse -S < %s | FileCheck %s
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
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target triple = "x86_64-apple-macosx10.7.0"
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; Sanity tests for atomic stores.
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; Note that it turns out essentially every transformation DSE does is legal on
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; atomic ops, just some transformations are not allowed across release-acquire pairs.
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@x = common global i32 0, align 4
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@y = common global i32 0, align 4
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declare void @randomop(i32*)
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; DSE across unordered store (allowed)
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define void @test1() {
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; CHECK-LABEL: test1
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; CHECK-NOT: store i32 0
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; CHECK: store i32 1
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store i32 0, i32* @x
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store atomic i32 0, i32* @y unordered, align 4
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store i32 1, i32* @x
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ret void
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}
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; DSE across seq_cst load (allowed)
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define i32 @test2() {
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; CHECK-LABEL: test2
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; CHECK-NOT: store i32 0
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; CHECK: store i32 1
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store i32 0, i32* @x
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%x = load atomic i32* @y seq_cst, align 4
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store i32 1, i32* @x
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ret i32 %x
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}
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; DSE across seq_cst store (allowed)
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define void @test3() {
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; CHECK-LABEL: test3
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; CHECK-NOT: store i32 0
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; CHECK: store atomic i32 2
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store i32 0, i32* @x
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store atomic i32 2, i32* @y seq_cst, align 4
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store i32 1, i32* @x
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ret void
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}
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; DSE remove unordered store (allowed)
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define void @test4() {
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; CHECK-LABEL: test4
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; CHECK-NOT: store atomic
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; CHECK: store i32 1
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store atomic i32 0, i32* @x unordered, align 4
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store i32 1, i32* @x
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ret void
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}
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; DSE unordered store overwriting non-atomic store (allowed)
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define void @test5() {
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; CHECK-LABEL: test5
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; CHECK: store atomic i32 1
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store i32 0, i32* @x
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store atomic i32 1, i32* @x unordered, align 4
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ret void
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}
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; DSE no-op unordered atomic store (allowed)
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define void @test6() {
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; CHECK-LABEL: test6
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; CHECK-NOT: store
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; CHECK: ret void
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%x = load atomic i32* @x unordered, align 4
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store atomic i32 %x, i32* @x unordered, align 4
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ret void
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}
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; DSE seq_cst store (be conservative; DSE doesn't have infrastructure
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; to reason about atomic operations).
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define void @test7() {
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; CHECK-LABEL: test7
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; CHECK: store atomic
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%a = alloca i32
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store atomic i32 0, i32* %a seq_cst, align 4
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ret void
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}
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; DSE and seq_cst load (be conservative; DSE doesn't have infrastructure
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; to reason about atomic operations).
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define i32 @test8() {
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; CHECK-LABEL: test8
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; CHECK: store
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; CHECK: load atomic
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%a = alloca i32
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call void @randomop(i32* %a)
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store i32 0, i32* %a, align 4
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%x = load atomic i32* @x seq_cst, align 4
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ret i32 %x
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}
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; DSE across monotonic load (allowed as long as the eliminated store isUnordered)
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define i32 @test9() {
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; CHECK-LABEL: test9
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; CHECK-NOT: store i32 0
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; CHECK: store i32 1
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store i32 0, i32* @x
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%x = load atomic i32* @y monotonic, align 4
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store i32 1, i32* @x
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ret i32 %x
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}
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; DSE across monotonic store (allowed as long as the eliminated store isUnordered)
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define void @test10() {
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; CHECK-LABEL: test10
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; CHECK-NOT: store i32 0
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; CHECK: store i32 1
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store i32 0, i32* @x
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store atomic i32 42, i32* @y monotonic, align 4
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store i32 1, i32* @x
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ret void
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}
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; DSE across monotonic load (forbidden since the eliminated store is atomic)
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define i32 @test11() {
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; CHECK-LABEL: test11
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; CHECK: store atomic i32 0
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; CHECK: store atomic i32 1
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store atomic i32 0, i32* @x monotonic, align 4
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%x = load atomic i32* @y monotonic, align 4
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store atomic i32 1, i32* @x monotonic, align 4
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ret i32 %x
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}
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; DSE across monotonic store (forbidden since the eliminated store is atomic)
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define void @test12() {
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; CHECK-LABEL: test12
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; CHECK: store atomic i32 0
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; CHECK: store atomic i32 1
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store atomic i32 0, i32* @x monotonic, align 4
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store atomic i32 42, i32* @y monotonic, align 4
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store atomic i32 1, i32* @x monotonic, align 4
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ret void
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}
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; DSE is allowed across a pair of an atomic read and then write.
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define i32 @test13() {
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; CHECK-LABEL: test13
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; CHECK-NOT: store i32 0
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; CHECK: store i32 1
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store i32 0, i32* @x
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%x = load atomic i32* @y seq_cst, align 4
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store atomic i32 %x, i32* @y seq_cst, align 4
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store i32 1, i32* @x
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ret i32 %x
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}
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; Same if it is acquire-release instead of seq_cst/seq_cst
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define i32 @test14() {
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; CHECK-LABEL: test14
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; CHECK-NOT: store i32 0
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; CHECK: store i32 1
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store i32 0, i32* @x
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%x = load atomic i32* @y acquire, align 4
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store atomic i32 %x, i32* @y release, align 4
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store i32 1, i32* @x
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ret i32 %x
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}
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; But DSE is not allowed across a release-acquire pair.
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define i32 @test15() {
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; CHECK-LABEL: test15
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; CHECK: store i32 0
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; CHECK: store i32 1
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store i32 0, i32* @x
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store atomic i32 0, i32* @y release, align 4
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%x = load atomic i32* @y acquire, align 4
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store i32 1, i32* @x
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ret i32 %x
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}
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