1; RUN: opt -S -basic-aa -dse < %s | FileCheck %s 2 3; We conservative choose to prevent dead store elimination 4; across release or stronger fences. It's not required 5; (since the must still be a race on %addd.i), but 6; it is conservatively correct. A legal optimization 7; could hoist the second store above the fence, and then 8; DSE one of them. 9define void @test1(i32* %addr.i) { 10; CHECK-LABEL: @test1 11; CHECK: store i32 5 12; CHECK: fence 13; CHECK: store i32 5 14; CHECK: ret 15 store i32 5, i32* %addr.i, align 4 16 fence release 17 store i32 5, i32* %addr.i, align 4 18 ret void 19} 20 21; Same as previous, but with different values. If we ever optimize 22; this more aggressively, this allows us to check that the correct 23; store is retained (the 'i32 1' store in this case) 24define void @test1b(i32* %addr.i) { 25; CHECK-LABEL: @test1b 26; CHECK: store i32 42 27; CHECK: fence release 28; CHECK: store i32 1 29; CHECK: ret 30 store i32 42, i32* %addr.i, align 4 31 fence release 32 store i32 1, i32* %addr.i, align 4 33 ret void 34} 35 36; We *could* DSE across this fence, but don't. No other thread can 37; observe the order of the acquire fence and the store. 38define void @test2(i32* %addr.i) { 39; CHECK-LABEL: @test2 40; CHECK: store 41; CHECK: fence 42; CHECK: store 43; CHECK: ret 44 store i32 5, i32* %addr.i, align 4 45 fence acquire 46 store i32 5, i32* %addr.i, align 4 47 ret void 48} 49