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JitArm64_Integer: cmpl - Subtract 12-bit constant

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You can encode a 12-bit immediate in a SUB instruction on ARM64. We can
exploit this to avoid materializing the immediate.

This approach saves an instruction if it does not need to be
materialized in a register afterwards. Otherwise, we just materialize
it later and the total number of instructions stays the same.

Before:
0x5280003a   mov    w26, #0x1                 ; =1
0xcb1a033b   sub    x27, x25, x26

After:
0xd100073b   sub    x27, x25, #0x1
This commit is contained in:
Sintendo 2025-02-01 21:11:23 +01:00
parent c5870ed0c7
commit b7c3f91643
1 changed files with 6 additions and 2 deletions
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8
Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
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@ -728,9 +728,13 @@ void JitArm64::cmpl(UGeckoInstruction inst)
{
NEG(CR, EncodeRegTo64(gpr.R(b)));
}
else if (gpr.IsImm(b) && !gpr.GetImm(b))
else if (gpr.IsImm(b) && (gpr.GetImm(b) & 0xFFF) == gpr.GetImm(b))
{
MOV(EncodeRegTo32(CR), gpr.R(a));
const u32 imm = gpr.GetImm(b);
if (imm == 0)
MOV(EncodeRegTo32(CR), gpr.R(a));
else
SUB(CR, EncodeRegTo64(gpr.R(a)), imm);
}
else
{