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llvm-project/llvm/test/Transforms/DeadStoreElimination/MSSA/multiblock-simple.ll
Florian Hahn 3a8372ed02 [DSE] Support traversing MemoryPhis. 
For MemoryPhis, we have to avoid that the MemoryPhi may be executed
before before the access we are currently looking at.

To do this we do a post-order numbering of the basic blocks in the
function and bail out once we reach a MemoryPhi with a larger (or equal)
post-order block number than the current MemoryAccess.
This changes the order in which we visit stores for elimination.

This patch also adds support for exploring multiple paths. We keep a worklist (ToCheck) of memory accesses that might be eliminated by our starting MemoryDef or MemoryPhis for further exploration.  For MemoryPhis, we add the incoming values to the worklist, for MemoryDefs we add the defining access.

Reviewers: dmgreen, rnk, efriedma, bryant, asbirlea

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D72148
2020-03-20 07:51:42 +00:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -basicaa -dse -enable-dse-memoryssa -S | FileCheck %s
target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
define void @test2(i32* noalias %P) {
; CHECK-LABEL: @test2(
; CHECK-NEXT: br i1 true, label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: br label [[BB3]]
; CHECK: bb3:
; CHECK-NEXT: store i32 0, i32* [[P:%.*]]
; CHECK-NEXT: ret void
;
store i32 1, i32* %P
br i1 true, label %bb1, label %bb2
bb1:
br label %bb3
bb2:
br label %bb3
bb3:
store i32 0, i32* %P
ret void
}
define void @test3(i32* noalias %P) {
; CHECK-LABEL: @test3(
; CHECK-NEXT: store i32 0, i32* [[P:%.*]]
; CHECK-NEXT: br i1 true, label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: store i32 0, i32* [[P]]
; CHECK-NEXT: br label [[BB3]]
; CHECK: bb3:
; CHECK-NEXT: ret void
;
store i32 0, i32* %P
br i1 true, label %bb1, label %bb2
bb1:
br label %bb3
bb2:
store i32 0, i32* %P
br label %bb3
bb3:
ret void
}
define void @test7(i32* noalias %P, i32* noalias %Q) {
; CHECK-LABEL: @test7(
; CHECK-NEXT: br i1 true, label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: [[TMP1:%.*]] = load i32, i32* [[P:%.*]]
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: br label [[BB3]]
; CHECK: bb3:
; CHECK-NEXT: store i32 0, i32* [[Q:%.*]]
; CHECK-NEXT: store i32 0, i32* [[P]]
; CHECK-NEXT: ret void
;
store i32 1, i32* %Q
br i1 true, label %bb1, label %bb2
bb1:
load i32, i32* %P
br label %bb3
bb2:
br label %bb3
bb3:
store i32 0, i32* %Q
store i32 0, i32* %P
ret void
}
define i32 @test22(i32* %P, i32* noalias %Q, i32* %R) {
; CHECK-LABEL: @test22(
; CHECK-NEXT: store i32 2, i32* [[P:%.*]]
; CHECK-NEXT: store i32 3, i32* [[Q:%.*]]
; CHECK-NEXT: [[L:%.*]] = load i32, i32* [[R:%.*]]
; CHECK-NEXT: ret i32 [[L]]
;
store i32 1, i32* %Q
store i32 2, i32* %P
store i32 3, i32* %Q
%l = load i32, i32* %R
ret i32 %l
}
define void @test9(i32* noalias %P) {
; CHECK-LABEL: @test9(
; CHECK-NEXT: store i32 0, i32* [[P:%.*]]
; CHECK-NEXT: br i1 true, label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: ret void
; CHECK: bb3:
; CHECK-NEXT: store i32 0, i32* [[P]]
; CHECK-NEXT: ret void
;
store i32 0, i32* %P
br i1 true, label %bb1, label %bb2
bb1:
br label %bb3
bb2:
ret void
bb3:
store i32 0, i32* %P
ret void
}
; We cannot eliminate `store i32 0, i32* %P`, as it is read by the later load.
; Make sure that we check the uses of `store i32 1, i32* %P.1 which does not
; alias %P. Note that uses point to the *first* def that may alias.
define void @overlapping_read(i32* %P) {
; CHECK-LABEL: @overlapping_read(
; CHECK-NEXT: store i32 0, i32* [[P:%.*]]
; CHECK-NEXT: [[P_1:%.*]] = getelementptr i32, i32* [[P]], i32 1
; CHECK-NEXT: store i32 1, i32* [[P_1]]
; CHECK-NEXT: [[P_64:%.*]] = bitcast i32* [[P]] to i64*
; CHECK-NEXT: [[LV:%.*]] = load i64, i64* [[P_64]]
; CHECK-NEXT: br i1 true, label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: br label [[BB3]]
; CHECK: bb3:
; CHECK-NEXT: store i32 2, i32* [[P]]
; CHECK-NEXT: ret void
;
store i32 0, i32* %P
%P.1 = getelementptr i32, i32* %P, i32 1
store i32 1, i32* %P.1
%P.64 = bitcast i32* %P to i64*
%lv = load i64, i64* %P.64
br i1 true, label %bb1, label %bb2
bb1:
br label %bb3
bb2:
br label %bb3
bb3:
store i32 2, i32* %P
ret void
}
define void @test10(i32* %P) {
; CHECK-LABEL: @test10(
; CHECK-NEXT: store i32 0, i32* [[P:%.*]]
; CHECK-NEXT: br i1 true, label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: store i32 0, i32* [[P]]
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: ret void
; CHECK: bb3:
; CHECK-NEXT: ret void
;
store i32 0, i32* %P
br i1 true, label %bb1, label %bb2
bb1:
store i32 0, i32* %P
br label %bb3
bb2:
ret void
bb3:
ret void
}
define void @test11() {
; CHECK-LABEL: @test11(
; CHECK-NEXT: [[P:%.*]] = alloca i32
; CHECK-NEXT: store i32 0, i32* [[P]]
; CHECK-NEXT: br i1 true, label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: store i32 0, i32* [[P]]
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: ret void
; CHECK: bb3:
; CHECK-NEXT: ret void
;
%P = alloca i32
store i32 0, i32* %P
br i1 true, label %bb1, label %bb2
bb1:
store i32 0, i32* %P
br label %bb3
bb2:
ret void
bb3:
ret void
}
define void @test12(i32* %P) {
; CHECK-LABEL: @test12(
; CHECK-NEXT: store i32 0, i32* [[P:%.*]]
; CHECK-NEXT: br i1 true, label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: store i32 1, i32* [[P]]
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: store i32 1, i32* [[P]]
; CHECK-NEXT: ret void
; CHECK: bb3:
; CHECK-NEXT: ret void
;
store i32 0, i32* %P
br i1 true, label %bb1, label %bb2
bb1:
store i32 1, i32* %P
br label %bb3
bb2:
store i32 1, i32* %P
ret void
bb3:
ret void
}
define void @test13(i32* %P) {
; CHECK-LABEL: @test13(
; CHECK-NEXT: store i32 0, i32* [[P:%.*]]
; CHECK-NEXT: br i1 true, label [[BB1:%.*]], label [[BB2:%.*]]
; CHECK: bb1:
; CHECK-NEXT: store i32 1, i32* [[P]]
; CHECK-NEXT: br label [[BB3:%.*]]
; CHECK: bb2:
; CHECK-NEXT: store i32 1, i32* [[P]]
; CHECK-NEXT: br label [[BB3]]
; CHECK: bb3:
; CHECK-NEXT: ret void
;
store i32 0, i32* %P
br i1 true, label %bb1, label %bb2
bb1:
store i32 1, i32* %P
br label %bb3
bb2:
store i32 1, i32* %P
br label %bb3
bb3:
ret void
}
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