[llvm] r354518 - [DAGCombine] Generalize Dead Store to overlapping stores.
Nirav Dave via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 20 13:07:50 PST 2019
Author: niravd
Date: Wed Feb 20 13:07:50 2019
New Revision: 354518
URL: http://llvm.org/viewvc/llvm-project?rev=354518&view=rev
Log:
[DAGCombine] Generalize Dead Store to overlapping stores.
Summary:
Remove stores that are immediately overwritten by larger
stores.
Reviewers: courbet, rnk
Reviewed By: rnk
Subscribers: javed.absar, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58467
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
llvm/trunk/test/CodeGen/AArch64/ldst-paired-aliasing.ll
llvm/trunk/test/CodeGen/X86/pr40631_deadstore_elision.ll
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=354518&r1=354517&r2=354518&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Wed Feb 20 13:07:50 2019
@@ -15414,25 +15414,28 @@ SDValue DAGCombiner::visitSTORE(SDNode *
if (StoreSDNode *ST1 = dyn_cast<StoreSDNode>(Chain)) {
if (ST->isUnindexed() && !ST->isVolatile() && ST1->isUnindexed() &&
- !ST1->isVolatile() && ST1->getBasePtr() == Ptr &&
- ST->getMemoryVT() == ST1->getMemoryVT()) {
- // If this is a store followed by a store with the same value to the same
- // location, then the store is dead/noop.
- if (ST1->getValue() == Value) {
- // The store is dead, remove it.
+ !ST1->isVolatile()) {
+ if (ST1->getBasePtr() == Ptr && ST1->getValue() == Value &&
+ ST->getMemoryVT() == ST1->getMemoryVT()) {
+ // If this is a store followed by a store with the same value to the
+ // same location, then the store is dead/noop.
return Chain;
}
- // If this is a store who's preceeding store to the same location
- // and no one other node is chained to that store we can effectively
- // drop the store. Do not remove stores to undef as they may be used as
- // data sinks.
if (OptLevel != CodeGenOpt::None && ST1->hasOneUse() &&
!ST1->getBasePtr().isUndef()) {
- // ST1 is fully overwritten and can be elided. Combine with it's chain
- // value.
- CombineTo(ST1, ST1->getChain());
- return SDValue();
+ const BaseIndexOffset STBase = BaseIndexOffset::match(ST, DAG);
+ const BaseIndexOffset ChainBase = BaseIndexOffset::match(ST1, DAG);
+ unsigned STByteSize = ST->getMemoryVT().getSizeInBits() / 8;
+ unsigned ChainByteSize = ST1->getMemoryVT().getSizeInBits() / 8;
+ // If this is a store who's preceeding store to a subset of the current
+ // location and no one other node is chained to that store we can
+ // effectively drop the store. Do not remove stores to undef as they may
+ // be used as data sinks.
+ if (STBase.contains(STByteSize, ChainBase, ChainByteSize, DAG)) {
+ CombineTo(ST1, ST1->getChain());
+ return SDValue();
+ }
}
}
}
Modified: llvm/trunk/test/CodeGen/AArch64/ldst-paired-aliasing.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/ldst-paired-aliasing.ll?rev=354518&r1=354517&r2=354518&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/ldst-paired-aliasing.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/ldst-paired-aliasing.ll Wed Feb 20 13:07:50 2019
@@ -10,11 +10,11 @@ declare void @llvm.memset.p0i8.i64(i8* n
define i32 @main() local_unnamed_addr #1 {
; Make sure the stores happen in the correct order (the exact instructions could change).
; CHECK-LABEL: main:
-; CHECK: stp xzr, xzr, [sp, #72]
+
+; CHECK: str xzr, [sp, #80]
; CHECK: str w9, [sp, #80]
-; CHECK: str q0, [sp, #48]
+; CHECK: stp q0, q0, [sp, #48]
; CHECK: ldr w8, [sp, #48]
-; CHECK: str q0, [sp, #64]
for.body.lr.ph.i.i.i.i.i.i63:
%b1 = alloca [10 x i32], align 16
Modified: llvm/trunk/test/CodeGen/X86/pr40631_deadstore_elision.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr40631_deadstore_elision.ll?rev=354518&r1=354517&r2=354518&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pr40631_deadstore_elision.ll (original)
+++ llvm/trunk/test/CodeGen/X86/pr40631_deadstore_elision.ll Wed Feb 20 13:07:50 2019
@@ -11,7 +11,6 @@ define i32 @ipt_do_table(%struct.sk_buff
; CHECK-NEXT: .cfi_def_cfa_offset 48
; CHECK-NEXT: movq (%rdi), %rax
; CHECK-NEXT: xorps %xmm0, %xmm0
-; CHECK-NEXT: movaps %xmm0, (%rsp)
; CHECK-NEXT: movaps %xmm0, {{[0-9]+}}(%rsp)
; CHECK-NEXT: movq $0, {{[0-9]+}}(%rsp)
; CHECK-NEXT: movaps {{.*#+}} xmm0 = [12297829382473034410,12297829382473034410]
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