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Revert r321089: "[DAG] Elide overlapping store" (and subsequent fix in r321204)

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Our internal testing has revealed has discovered bugs in PPC builds.
I have forward reproduction instructions to the original author (Nirav).

llvm-svn: 321649
This commit is contained in:
Daniel Jasper 2018-01-02 14:38:52 +00:00
parent c92c581b30
commit c0d636a5d6
2 changed files with 23 additions and 22 deletions
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40
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -13782,30 +13782,30 @@ SDValue DAGCombiner::visitSTORE(SDNode *N) {
}
}
// Deal with elidable overlapping chained stores.
if (StoreSDNode *ST1 = dyn_cast<StoreSDNode>(Chain))
if (OptLevel != CodeGenOpt::None && ST->isUnindexed() &&
ST1->isUnindexed() && !ST1->isVolatile() && ST1->hasOneUse() &&
!ST1->getBasePtr().isUndef() && !ST->isVolatile()) {
BaseIndexOffset STBasePtr = BaseIndexOffset::match(ST->getBasePtr(), DAG);
BaseIndexOffset ST1BasePtr =
BaseIndexOffset::match(ST1->getBasePtr(), DAG);
unsigned STBytes = ST->getMemoryVT().getStoreSize();
unsigned ST1Bytes = ST1->getMemoryVT().getStoreSize();
int64_t PtrDiff;
// If this is a store who's preceeding store to a subset of the same
// memory 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 (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.
return Chain;
}
if (((ST->getBasePtr() == ST1->getBasePtr()) &&
(ST->getValue() == ST1->getValue())) ||
(STBasePtr.equalBaseIndex(ST1BasePtr, DAG, PtrDiff) &&
(0 <= PtrDiff) && (PtrDiff + ST1Bytes <= STBytes))) {
// 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(N, 0);
return SDValue();
}
}
}
// If this is an FP_ROUND or TRUNC followed by a store, fold this into a
// truncating store. We can do this even if this is already a truncstore.

5
test/CodeGen/AArch64/ldst-paired-aliasing.ll
View File

@ -10,10 +10,11 @@ declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) #3
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: str xzr, [sp, #80]
; CHECK: stp xzr, xzr, [sp, #72]
; CHECK: str w9, [sp, #80]
; CHECK: stp q0, q0, [sp, #48]
; CHECK: str 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