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DAGCombiner: fix use-counting issue when forming zextload

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DAGCombiner was counting all uses of a load node  when considering whether it's
worth combining into a zextload. Really, it wants to ignore the chain and just
count real uses.

rdar://problem/13896307

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185419 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover 2013-07-02 09:58:53 +00:00
parent b19dd2bcaf
commit 5bce67a95f
2 changed files with 17 additions and 1 deletions
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2
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -2755,7 +2755,7 @@ SDValue DAGCombiner::visitAND(SDNode *N) {
? cast<LoadSDNode>(N0.getOperand(0))
: cast<LoadSDNode>(N0);
if (LN0->getExtensionType() != ISD::SEXTLOAD &&
LN0->isUnindexed() && N0.hasOneUse() && LN0->hasOneUse()) {
LN0->isUnindexed() && N0.hasOneUse() && SDValue(LN0, 0).hasOneUse()) {
uint32_t ActiveBits = N1C->getAPIntValue().getActiveBits();
if (ActiveBits > 0 && APIntOps::isMask(ActiveBits, N1C->getAPIntValue())){
EVT ExtVT = EVT::getIntegerVT(*DAG.getContext(), ActiveBits);

16
test/CodeGen/X86/simple-zext.ll Normal file
View File

@ -0,0 +1,16 @@
; RUN: llc -mtriple=x86_64-apple-darwin < %s| FileCheck %s
; A bug in DAGCombiner prevented it forming a zextload in this simple case
; because it counted both the chain user and the real user against the
; profitability total.
define void @load_zext(i32* nocapture %p){
entry:
%0 = load i32* %p, align 4
%and = and i32 %0, 255
tail call void @use(i32 %and)
ret void
; CHECK: movzbl ({{%r[a-z]+}}), {{%e[a-z]+}}
}
declare void @use(i32)