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Redundant store instructions should be removed as dead code

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218493 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Xu 2014-09-26 02:02:09 +00:00
parent 55a90ab4ef
commit c41ae2a5c4
2 changed files with 37 additions and 0 deletions
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14
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -9799,6 +9799,20 @@ SDValue DAGCombiner::visitSTORE(SDNode *N) {
return Chain;
}
}
// If this is a store followed by a store with the same value to the same
// location, then the store is dead/noop.
if (StoreSDNode *ST1 = dyn_cast<StoreSDNode>(Chain)) {
if (ST1->getBasePtr() == Ptr && ST->getMemoryVT() == ST1->getMemoryVT() &&
ST1->getValue() == Value && ST->isUnindexed() && !ST->isVolatile() &&
ST1->isUnindexed() &&
!ST1->isVolatile() &&
// There can't be any side effects between the two stores, such as
// a call or store.
Chain.reachesChainWithoutSideEffects(SDValue(ST1, 0))) {
// The store is dead, remove it.
return Chain;
}
}
// 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.

23
test/CodeGen/AArch64/Redundantstore.ll Normal file
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@ -0,0 +1,23 @@
;llc -O3 -march=aarch64 < %s | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
@end_of_array = common global i8* null, align 8
; CHECK-LABLE: @test
; CHECK: stur
; CHECK-NOT: stur
define i8* @test(i32 %size) {
entry:
%0 = load i8** @end_of_array, align 8
%conv = sext i32 %size to i64
%and = and i64 %conv, -8
%conv2 = trunc i64 %and to i32
%add.ptr.sum = add nsw i64 %and, -4
%add.ptr3 = getelementptr inbounds i8* %0, i64 %add.ptr.sum
%size4 = bitcast i8* %add.ptr3 to i32*
store i32 %conv2, i32* %size4, align 4
%add.ptr.sum9 = add nsw i64 %and, -4
%add.ptr5 = getelementptr inbounds i8* %0, i64 %add.ptr.sum9
%size6 = bitcast i8* %add.ptr5 to i32*
store i32 %conv2, i32* %size6, align 4
ret i8* %0
}