ShuriZma
/
dolphin
mirror of https://github.com/dolphin-emu/dolphin.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

JitArm64: creqv/crorc setting eq bit 

When I wrote 71e9766519, there was an interaction I didn't take into
account: When setting eq, SetCRFieldBit assumes that all bits in the
passed-in host register except the least significant bit are 0. But if
we use EON or ORN, all bits except the least significant bit get set to
1. This can cause eq to end up unset when it should be set.

This commit fixes the issue.

crandc is unaffected by the issue because the "1" bits get ANDed with
"0" bits from the first operand.

Note that in practice, we never have both bits_1_to_31_are_set and
negate at once, so while it looks like this commit adds an extra AND
instruction in some cases, those cases don't happen in practice, meaning
this fix shouldn't affect performance.
This commit is contained in:
JosJuice 2025-01-06 09:36:01 +01:00
parent 93fc5c02ac
commit aa9696e1c1
2 changed files with 15 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
Source/Core/Core/PowerPC/JitArm64/Jit.h
View File

@ -356,7 +356,10 @@ protected:
void WriteBLRExit(Arm64Gen::ARM64Reg dest);
void GetCRFieldBit(int field, int bit, Arm64Gen::ARM64Reg out);
void SetCRFieldBit(int field, int bit, Arm64Gen::ARM64Reg in, bool negate = false);
// This assumes that all bits except for bit 0 (LSB) are set to 0. But if bits_1_to_31_are_set
// equals true, it instead assumes that all of bits 1 to 31 are set.
void SetCRFieldBit(int field, int bit, Arm64Gen::ARM64Reg in, bool negate = false,
bool bits_1_to_31_are_set = false);
void ClearCRFieldBit(int field, int bit);
void SetCRFieldBit(int field, int bit);
void FixGTBeforeSettingCRFieldBit(Arm64Gen::ARM64Reg reg);

16
Source/Core/Core/PowerPC/JitArm64/JitArm64_SystemRegisters.cpp
View File

@ -50,7 +50,8 @@ void JitArm64::GetCRFieldBit(int field, int bit, ARM64Reg out)
}
}
void JitArm64::SetCRFieldBit(int field, int bit, ARM64Reg in, bool negate)
void JitArm64::SetCRFieldBit(int field, int bit, ARM64Reg in, bool negate,
bool bits_1_to_31_are_set)
{
gpr.BindCRToRegister(field, true);
ARM64Reg CR = gpr.CR(field);
@ -70,7 +71,9 @@ void JitArm64::SetCRFieldBit(int field, int bit, ARM64Reg in, bool negate)
AND(CR, CR, LogicalImm(0xFFFF'FFFF'0000'0000, GPRSize::B64));
ORR(CR, CR, in);
if (!negate)
EOR(CR, CR, LogicalImm(1ULL << 0, GPRSize::B64));
EOR(CR, CR, LogicalImm(bits_1_to_31_are_set ? 0xFFFF'FFFFULL : 1ULL, GPRSize::B64));
else if (bits_1_to_31_are_set)
AND(CR, CR, LogicalImm(0xFFFF'FFFF'0000'0001ULL, GPRSize::B64));
break;
case PowerPC::CR_GT_BIT: // set bit 63 to !input
@ -634,6 +637,7 @@ void JitArm64::crXXX(UGeckoInstruction inst)
// crnor or crnand
const bool negate_result = inst.SUBOP10 == 33 || inst.SUBOP10 == 225;
bool bits_1_to_31_are_set = false;
auto WA = gpr.GetScopedReg();
ARM64Reg XA = EncodeRegTo64(WA);
@ -661,7 +665,8 @@ void JitArm64::crXXX(UGeckoInstruction inst)
break;
case 289: // creqv: ~(A ^ B) = A ^ ~B
EON(XA, XA, XB);
EON(WA, WA, WB);
bits_1_to_31_are_set = true;
break;
case 33: // crnor: ~(A || B)
@ -670,13 +675,14 @@ void JitArm64::crXXX(UGeckoInstruction inst)
break;
case 417: // crorc: A || ~B
ORN(XA, XA, XB);
ORN(WA, WA, WB);
bits_1_to_31_are_set = true;
break;
}
}
// Store result bit in CRBD
SetCRFieldBit(inst.CRBD >> 2, 3 - (inst.CRBD & 3), XA, negate_result);
SetCRFieldBit(inst.CRBD >> 2, 3 - (inst.CRBD & 3), XA, negate_result, bits_1_to_31_are_set);
}
void JitArm64::mfcr(UGeckoInstruction inst)