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Revert rGbbeb08497ce58 "Revert "[GlobalISel] GISelKnownBits::computeKnownBitsImpl - Replace TargetOpcode::G_MUL handling with the common KnownBits::computeForMul implementation""

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Updated the GISel KnownBits tests as KnownBits::computeForMul allows more accurate computation.
This commit is contained in:
Simon Pilgrim 2020-11-05 10:39:53 +00:00
parent 2730f84bd0
commit 983601ea81
2 changed files with 3 additions and 16 deletions
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15
lib/CodeGen/GlobalISel/GISelKnownBits.cpp
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@ -287,20 +287,7 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known,
Depth + 1);
computeKnownBitsImpl(MI.getOperand(1).getReg(), Known2, DemandedElts,
Depth + 1);
// If low bits are zero in either operand, output low known-0 bits.
// Also compute a conservative estimate for high known-0 bits.
// More trickiness is possible, but this is sufficient for the
// interesting case of alignment computation.
unsigned TrailZ =
Known.countMinTrailingZeros() + Known2.countMinTrailingZeros();
unsigned LeadZ =
std::max(Known.countMinLeadingZeros() + Known2.countMinLeadingZeros(),
BitWidth) -
BitWidth;
Known.resetAll();
Known.Zero.setLowBits(std::min(TrailZ, BitWidth));
Known.Zero.setHighBits(std::min(LeadZ, BitWidth));
Known = KnownBits::computeForMul(Known, Known2);
break;
}
case TargetOpcode::G_SELECT: {

4
unittests/CodeGen/GlobalISel/KnownBitsTest.cpp
View File

@ -300,8 +300,8 @@ TEST_F(AArch64GISelMITest, TestKnownBits) {
GISelKnownBits Info(*MF);
KnownBits Known = Info.getKnownBits(SrcReg);
EXPECT_FALSE(Known.hasConflict());
EXPECT_EQ(0u, Known.One.getZExtValue());
EXPECT_EQ(31u, Known.Zero.getZExtValue());
EXPECT_EQ(32u, Known.One.getZExtValue());
EXPECT_EQ(95u, Known.Zero.getZExtValue());
APInt Zeroes = Info.getKnownZeroes(SrcReg);
EXPECT_EQ(Known.Zero, Zeroes);
}