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From c20838176e8bea9e5a176c59c78bbce9051ec987 Mon Sep 17 00:00:00 2001
From: Naveen Saini <naveen.kumar.saini@intel.com>
Date: Fri, 27 Aug 2021 11:41:47 +0800
Subject: [PATCH 2/2] [X86] When storing v1i1/v2i1/v4i1 to memory, make sure we
store zeros in the rest of the byte
We can't store garbage in the unused bits. It possible that something like zextload from i1/i2/i4 is created to read the memory. Those zextloads would be legalized assuming the extra bits are 0.
I'm not sure that the code in lowerStore is executed for the v1i1/v2i1/v4i1 case. It looks like the DAG combine in combineStore may have converted them to v8i1 first. And I think we're missing some cases to avoid going to the stack in the first place. But I don't have time to investigate those things at the moment so I wanted to focus on the correctness issue.
Should fix PR48147.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D91294
Upstream-Status: Backport [https://github.com/llvm/llvm-project/commit/a4124e455e641db1e18d4221d2dacb31953fd13b]
Signed-off-by: Naveen Saini <naveen.kumar.saini@intel.com>
---
llvm/lib/Target/X86/X86ISelLowering.cpp | 19 ++++++++++++++-----
llvm/lib/Target/X86/X86InstrAVX512.td | 3 ---
2 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 56690c3c555b..7e673a3163b7 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -23549,17 +23549,22 @@ static SDValue LowerStore(SDValue Op, const X86Subtarget &Subtarget,
// Without AVX512DQ, we need to use a scalar type for v2i1/v4i1/v8i1 stores.
if (StoredVal.getValueType().isVector() &&
StoredVal.getValueType().getVectorElementType() == MVT::i1) {
- assert(StoredVal.getValueType().getVectorNumElements() <= 8 &&
- "Unexpected VT");
+ unsigned NumElts = StoredVal.getValueType().getVectorNumElements();
+ assert(NumElts <= 8 && "Unexpected VT");
assert(!St->isTruncatingStore() && "Expected non-truncating store");
assert(Subtarget.hasAVX512() && !Subtarget.hasDQI() &&
"Expected AVX512F without AVX512DQI");
+ // We must pad with zeros to ensure we store zeroes to any unused bits.
StoredVal = DAG.getNode(ISD::INSERT_SUBVECTOR, dl, MVT::v16i1,
DAG.getUNDEF(MVT::v16i1), StoredVal,
DAG.getIntPtrConstant(0, dl));
StoredVal = DAG.getBitcast(MVT::i16, StoredVal);
StoredVal = DAG.getNode(ISD::TRUNCATE, dl, MVT::i8, StoredVal);
+ // Make sure we store zeros in the extra bits.
+ if (NumElts < 8)
+ StoredVal = DAG.getZeroExtendInReg(StoredVal, dl,
+ MVT::getIntegerVT(NumElts));
return DAG.getStore(St->getChain(), dl, StoredVal, St->getBasePtr(),
St->getPointerInfo(), St->getOriginalAlign(),
@@ -44133,17 +44138,21 @@ static SDValue combineStore(SDNode *N, SelectionDAG &DAG,
if (VT == MVT::v1i1 && VT == StVT && Subtarget.hasAVX512() &&
StoredVal.getOpcode() == ISD::SCALAR_TO_VECTOR &&
StoredVal.getOperand(0).getValueType() == MVT::i8) {
- return DAG.getStore(St->getChain(), dl, StoredVal.getOperand(0),
+ SDValue Val = StoredVal.getOperand(0);
+ // We must store zeros to the unused bits.
+ Val = DAG.getZeroExtendInReg(Val, dl, MVT::i1);
+ return DAG.getStore(St->getChain(), dl, Val,
St->getBasePtr(), St->getPointerInfo(),
St->getOriginalAlign(),
St->getMemOperand()->getFlags());
}
// Widen v2i1/v4i1 stores to v8i1.
- if ((VT == MVT::v2i1 || VT == MVT::v4i1) && VT == StVT &&
+ if ((VT == MVT::v1i1 || VT == MVT::v2i1 || VT == MVT::v4i1) && VT == StVT &&
Subtarget.hasAVX512()) {
unsigned NumConcats = 8 / VT.getVectorNumElements();
- SmallVector<SDValue, 4> Ops(NumConcats, DAG.getUNDEF(VT));
+ // We must store zeros to the unused bits.
+ SmallVector<SDValue, 4> Ops(NumConcats, DAG.getConstant(0, dl, VT));
Ops[0] = StoredVal;
StoredVal = DAG.getNode(ISD::CONCAT_VECTORS, dl, MVT::v8i1, Ops);
return DAG.getStore(St->getChain(), dl, StoredVal, St->getBasePtr(),
diff --git a/llvm/lib/Target/X86/X86InstrAVX512.td b/llvm/lib/Target/X86/X86InstrAVX512.td
index a3ad0b1c8dd6..aa1ccec02f2a 100644
--- a/llvm/lib/Target/X86/X86InstrAVX512.td
+++ b/llvm/lib/Target/X86/X86InstrAVX512.td
@@ -2871,9 +2871,6 @@ def : Pat<(i64 (bitconvert (v64i1 VK64:$src))),
// Load/store kreg
let Predicates = [HasDQI] in {
- def : Pat<(store VK1:$src, addr:$dst),
- (KMOVBmk addr:$dst, (COPY_TO_REGCLASS VK1:$src, VK8))>;
-
def : Pat<(v1i1 (load addr:$src)),
(COPY_TO_REGCLASS (KMOVBkm addr:$src), VK1)>;
def : Pat<(v2i1 (load addr:$src)),
--
2.17.1
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