llvm/test/CodeGen/AArch64/ldst-zero.ll
Nirav Dave acc2c1d71d Elide stores which are overwritten without being observed.
Summary:
In SelectionDAG, when a store is immediately chained to another store
to the same address, elide the first store as it has no observable
effects. This is causes small improvements dealing with intrinsics
lowered to stores.

Test notes:

* Many testcases overwrite store addresses multiple times and needed
  minor changes, mainly making stores volatile to prevent the
  optimization from optimizing the test away.

* Many X86 test cases optimized out instructions associated with
  associated with va_start.

* Note that test_splat in CodeGen/AArch64/misched-stp.ll no longer has
  dependencies to check and can probably be removed and potentially
  replaced with another test.

Reviewers: rnk, john.brawn

Subscribers: aemerson, rengolin, qcolombet, jyknight, nemanjai, nhaehnle, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D33206

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303198 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-16 19:43:56 +00:00

72 lines
2.7 KiB
LLVM

; RUN: llc -mtriple=aarch64 -mcpu=cortex-a53 < %s | FileCheck %s
; Tests to check that zero stores which are generated as STP xzr, xzr aren't
; scheduled incorrectly due to incorrect alias information
declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1)
%struct.tree_common = type { i8*, i8*, i32 }
; Original test case which exhibited the bug
define void @test1(%struct.tree_common* %t, i32 %code, i8* %type) {
; CHECK-LABEL: test1:
; CHECK-DAG: stp x2, xzr, [x0, #8]
; CHECK-DAG: str w1, [x0, #16]
; CHECK-DAG: str xzr, [x0]
entry:
%0 = bitcast %struct.tree_common* %t to i8*
tail call void @llvm.memset.p0i8.i64(i8* %0, i8 0, i64 24, i32 8, i1 false)
%code1 = getelementptr inbounds %struct.tree_common, %struct.tree_common* %t, i64 0, i32 2
store i32 %code, i32* %code1, align 8
%type2 = getelementptr inbounds %struct.tree_common, %struct.tree_common* %t, i64 0, i32 1
store i8* %type, i8** %type2, align 8
ret void
}
; Store to each struct element instead of using memset
define void @test2(%struct.tree_common* %t, i32 %code, i8* %type) {
; CHECK-LABEL: test2:
; CHECK-DAG: str w1, [x0, #16]
; CHECK-DAG: stp xzr, x2, [x0]
entry:
%0 = getelementptr inbounds %struct.tree_common, %struct.tree_common* %t, i64 0, i32 0
%1 = getelementptr inbounds %struct.tree_common, %struct.tree_common* %t, i64 0, i32 1
%2 = getelementptr inbounds %struct.tree_common, %struct.tree_common* %t, i64 0, i32 2
store i8* zeroinitializer, i8** %0, align 8
store i8* zeroinitializer, i8** %1, align 8
store i32 zeroinitializer, i32* %2, align 8
store i32 %code, i32* %2, align 8
store i8* %type, i8** %1, align 8
ret void
}
; Vector store instead of memset
define void @test3(%struct.tree_common* %t, i32 %code, i8* %type) {
; CHECK-LABEL: test3:
; CHECK-DAG: stp x2, xzr, [x0, #8]
; CHECK-DAG: str w1, [x0, #16]
; CHECK-DAG: str xzr, [x0]
entry:
%0 = bitcast %struct.tree_common* %t to <3 x i64>*
store <3 x i64> zeroinitializer, <3 x i64>* %0, align 8
%code1 = getelementptr inbounds %struct.tree_common, %struct.tree_common* %t, i64 0, i32 2
store i32 %code, i32* %code1, align 8
%type2 = getelementptr inbounds %struct.tree_common, %struct.tree_common* %t, i64 0, i32 1
store i8* %type, i8** %type2, align 8
ret void
}
; Vector store, then store to vector elements
define void @test4(<3 x i64>* %p, i64 %x, i64 %y) {
; CHECK-LABEL: test4:
; CHECK-DAG: stp x2, x1, [x0, #8]
; CHECK-DAG: str xzr, [x0]
entry:
store <3 x i64> zeroinitializer, <3 x i64>* %p, align 8
%0 = bitcast <3 x i64>* %p to i64*
%1 = getelementptr inbounds i64, i64* %0, i64 2
store i64 %x, i64* %1, align 8
%2 = getelementptr inbounds i64, i64* %0, i64 1
store i64 %y, i64* %2, align 8
ret void
}