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[M68k] Tidy up some bit shifting during code emission 

This fixes some issues with bit masking when emitting instructions
(including one TODO).

Differential Revision: https://reviews.llvm.org/D98527
This commit is contained in:
Ricky Taylor 2021-03-14 11:53:14 -07:00 committed by Min-Yih Hsu
parent 9f015757de
commit 84094fb4fd
1 changed files with 5 additions and 10 deletions
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15
llvm/lib/Target/M68k/MCTargetDesc/M68kMCCodeEmitter.cpp
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@ -162,13 +162,13 @@ unsigned M68kMCCodeEmitter::encodeReg(unsigned ThisByte, uint8_t Bead,
unsigned Written = 0;
if (Reg) {
uint32_t Val = RI->getEncodingValue(RegNum);
Buffer |= Val << Offset;
Buffer |= (Val & 7) << Offset;
Offset += 3;
Written += 3;
}
if (DA) {
Buffer |= (char)M68kII::isAddressRegister(RegNum) << Offset;
Buffer |= (uint64_t)M68kII::isAddressRegister(RegNum) << Offset;
Written++;
}
@ -179,13 +179,9 @@ static unsigned EmitConstant(uint64_t Val, unsigned Size, unsigned Pad,
uint64_t &Buffer, unsigned Offset) {
assert(Size + Offset <= 64 && isUIntN(Size, Val) && "Value does not fit");
// Pad the instruction with zeros if any
// FIXME Emit zeros in the padding, since there might be trash in the buffer.
Size += Pad;
// Writing Value in host's endianness
Buffer |= Val << Offset;
return Size;
Buffer |= (Val & ((1ULL << Size) - 1)) << Offset;
return Size + Pad;
}
unsigned M68kMCCodeEmitter::encodeImm(unsigned ThisByte, uint8_t Bead,
@ -316,8 +312,7 @@ unsigned M68kMCCodeEmitter::encodeImm(unsigned ThisByte, uint8_t Bead,
return Size;
}
return EmitConstant(Imm & (UINT64_MAX >> (64 - Size)), Size, Pad, Buffer,
Offset);
return EmitConstant(Imm & ((1ULL << Size) - 1), Size, Pad, Buffer, Offset);
}
#include "M68kGenMCCodeBeads.inc"