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GlobalISel: Implement known bits for G_MERGE_VALUES

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This commit is contained in:
Matt Arsenault 2020-08-27 12:15:16 -04:00
parent 510acaee86
commit b3488037c4
3 changed files with 41 additions and 0 deletions
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6
include/llvm/Support/KnownBits.h
View File

@ -241,6 +241,12 @@ public:
static KnownBits computeForAddSub(bool Add, bool NSW, const KnownBits &LHS,
KnownBits RHS);
/// Insert the bits from a smaller known bits starting at bitPosition.
void insertBits(const KnownBits &SubBits, unsigned BitPosition) {
Zero.insertBits(SubBits.Zero, BitPosition);
One.insertBits(SubBits.One, BitPosition);
}
/// Update known bits based on ANDing with RHS.
KnownBits &operator&=(const KnownBits &RHS);

12
lib/CodeGen/GlobalISel/GISelKnownBits.cpp
View File

@ -387,6 +387,18 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known,
Known.Zero.setBitsFrom(SrcBitWidth);
break;
}
case TargetOpcode::G_MERGE_VALUES: {
Register NumOps = MI.getNumOperands();
unsigned OpSize = MRI.getType(MI.getOperand(1).getReg()).getSizeInBits();
for (unsigned I = 0; I != NumOps - 1; ++I) {
KnownBits SrcOpKnown;
computeKnownBitsImpl(MI.getOperand(I + 1).getReg(), SrcOpKnown,
DemandedElts, Depth + 1);
Known.insertBits(SrcOpKnown, I * OpSize);
}
break;
}
}
assert(!Known.hasConflict() && "Bits known to be one AND zero?");

23
unittests/CodeGen/GlobalISel/KnownBitsTest.cpp
View File

@ -555,3 +555,26 @@ TEST_F(AArch64GISelMITest, TestKnownBitsExt) {
EXPECT_EQ((uint64_t)0, Res.One.getZExtValue());
EXPECT_EQ((uint64_t)0xfffffffe, Res.Zero.getZExtValue());
}
TEST_F(AArch64GISelMITest, TestKnownBitsMergeValues) {
StringRef MIRString = R"(
%val0:_(s16) = G_CONSTANT i16 35224
%val1:_(s16) = G_CONSTANT i16 17494
%val2:_(s16) = G_CONSTANT i16 4659
%val3:_(s16) = G_CONSTANT i16 43981
%merge:_(s64) = G_MERGE_VALUES %val0, %val1, %val2, %val3
%mergecopy:_(s64) = COPY %merge
)";
setUp(MIRString);
if (!TM)
return;
const uint64_t TestVal = UINT64_C(0xabcd123344568998);
Register CopyMerge = Copies[Copies.size() - 1];
GISelKnownBits Info(*MF);
KnownBits Res = Info.getKnownBits(CopyMerge);
EXPECT_EQ(64u, Res.getBitWidth());
EXPECT_EQ(TestVal, Res.One.getZExtValue());
EXPECT_EQ(~TestVal, Res.Zero.getZExtValue());
}