forked from OSchip/llvm-project
87 lines
2.6 KiB
LLVM
87 lines
2.6 KiB
LLVM
; RUN: opt -S -early-cse < %s | FileCheck %s
|
|
; NOTE: This file is testing the current implementation. Some of
|
|
; the transforms used as negative tests below would be legal, but
|
|
; only if reached through a chain of logic which EarlyCSE is incapable
|
|
; of performing. To say it differently, this file tests a conservative
|
|
; version of the memory model. If we want to extend EarlyCSE to be more
|
|
; aggressive in the future, we may need to relax some of the negative tests.
|
|
|
|
; We can value forward across the fence since we can (semantically)
|
|
; reorder the following load before the fence.
|
|
define i32 @test(i32* %addr.i) {
|
|
; CHECK-LABEL: @test
|
|
; CHECK: store
|
|
; CHECK: fence
|
|
; CHECK-NOT: load
|
|
; CHECK: ret
|
|
store i32 5, i32* %addr.i, align 4
|
|
fence release
|
|
%a = load i32, i32* %addr.i, align 4
|
|
ret i32 %a
|
|
}
|
|
|
|
; Same as above
|
|
define i32 @test2(i32* noalias %addr.i, i32* noalias %otheraddr) {
|
|
; CHECK-LABEL: @test2
|
|
; CHECK: load
|
|
; CHECK: fence
|
|
; CHECK-NOT: load
|
|
; CHECK: ret
|
|
%a = load i32, i32* %addr.i, align 4
|
|
fence release
|
|
%a2 = load i32, i32* %addr.i, align 4
|
|
%res = sub i32 %a, %a2
|
|
ret i32 %a
|
|
}
|
|
|
|
; We can not value forward across an acquire barrier since we might
|
|
; be syncronizing with another thread storing to the same variable
|
|
; followed by a release fence. If this thread observed the release
|
|
; had happened, we must present a consistent view of memory at the
|
|
; fence. Note that it would be legal to reorder '%a' after the fence
|
|
; and then remove '%a2'. The current implementation doesn't know how
|
|
; to do this, but if it learned, this test will need revised.
|
|
define i32 @test3(i32* noalias %addr.i, i32* noalias %otheraddr) {
|
|
; CHECK-LABEL: @test3
|
|
; CHECK: load
|
|
; CHECK: fence
|
|
; CHECK: load
|
|
; CHECK: sub
|
|
; CHECK: ret
|
|
%a = load i32, i32* %addr.i, align 4
|
|
fence acquire
|
|
%a2 = load i32, i32* %addr.i, align 4
|
|
%res = sub i32 %a, %a2
|
|
ret i32 %res
|
|
}
|
|
|
|
; We can not dead store eliminate accross the fence. We could in
|
|
; principal reorder the second store above the fence and then DSE either
|
|
; store, but this is beyond the simple last-store DSE which EarlyCSE
|
|
; implements.
|
|
define void @test4(i32* %addr.i) {
|
|
; CHECK-LABEL: @test4
|
|
; CHECK: store
|
|
; CHECK: fence
|
|
; CHECK: store
|
|
; CHECK: ret
|
|
store i32 5, i32* %addr.i, align 4
|
|
fence release
|
|
store i32 5, i32* %addr.i, align 4
|
|
ret void
|
|
}
|
|
|
|
; We *could* DSE across this fence, but don't. No other thread can
|
|
; observe the order of the acquire fence and the store.
|
|
define void @test5(i32* %addr.i) {
|
|
; CHECK-LABEL: @test5
|
|
; CHECK: store
|
|
; CHECK: fence
|
|
; CHECK: store
|
|
; CHECK: ret
|
|
store i32 5, i32* %addr.i, align 4
|
|
fence acquire
|
|
store i32 5, i32* %addr.i, align 4
|
|
ret void
|
|
}
|