maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[unordered] unordered loads from null are still unreachable 

llvm-svn: 267019
This commit is contained in:
Philip Reames 2016-04-21 17:45:05 +00:00
parent e26b50e71a
commit 3ac0718423
2 changed files with 58 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
View File

@ -836,9 +836,9 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
LI.getName() + ".cast"));
}
// None of the following transforms are legal for volatile/atomic loads.
// FIXME: Some of it is okay for atomic loads; needs refactoring.
if (!LI.isSimple()) return nullptr;
// None of the following transforms are legal for volatile/ordered atomic
// loads. Most of them do apply for unordered atomics.
if (!LI.isUnordered()) return nullptr;
// load(gep null, ...) -> unreachable
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
@ -867,6 +867,10 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
return replaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
// TODO: The transform below needs updated for unordered loads
if (!LI.isSimple())
return nullptr;
if (Op->hasOneUse()) {
// Change select and PHI nodes to select values instead of addresses: this
// helps alias analysis out a lot, allows many others simplifications, and

51
llvm/test/Transforms/InstCombine/atomic.ll
View File

@ -93,3 +93,54 @@ define i32 @test8(i32* %p) {
ret i32 %z
}
; An unordered access to null is still unreachable. There's no
; ordering imposed.
define i32 @test9() {
; CHECK-LABEL: define i32 @test9(
; CHECK: store i32 undef, i32* null
%x = load atomic i32, i32* null unordered, align 4
ret i32 %x
}
; FIXME: Could also fold
define i32 @test10() {
; CHECK-LABEL: define i32 @test10(
; CHECK: load atomic i32, i32* null monotonic
%x = load atomic i32, i32* null monotonic, align 4
ret i32 %x
}
; Would this be legal to fold? Probably?
define i32 @test11() {
; CHECK-LABEL: define i32 @test11(
; CHECK: load atomic i32, i32* null seq_cst
%x = load atomic i32, i32* null seq_cst, align 4
ret i32 %x
}
; An unordered access to null is still unreachable. There's no
; ordering imposed.
define i32 @test12() {
; CHECK-LABEL: define i32 @test12(
; CHECK: store atomic i32 undef, i32* null
store atomic i32 0, i32* null unordered, align 4
ret i32 0
}
; FIXME: Could also fold
define i32 @test13() {
; CHECK-LABEL: define i32 @test13(
; CHECK: store atomic i32 0, i32* null monotonic
store atomic i32 0, i32* null monotonic, align 4
ret i32 0
}
; Would this be legal to fold? Probably?
define i32 @test14() {
; CHECK-LABEL: define i32 @test14(
; CHECK: store atomic i32 0, i32* null seq_cst
store atomic i32 0, i32* null seq_cst, align 4
ret i32 0
}