From e3d889feb17782804061233f01bbf7ae691b4fac Mon Sep 17 00:00:00 2001
From: Sintendo <3380580+Sintendo@users.noreply.github.com>
Date: Sun, 3 Aug 2025 09:41:44 +0200
Subject: [PATCH 1/4] JitArm64_Integer: subfcx - Optimize a == 0

This case can be handled as a move. It also generates a constant carry
flag.

Before:
0x52800013   mov    w19, #0x0                 ; =0
0x6b1302b3   subs   w19, w21, w19

After:
0x2a1503f3   mov    w19, w21
---
 .../Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp   | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
index df2b48631da..31b8f96f71e 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -1432,6 +1432,17 @@ void JitArm64::subfcx(UGeckoInstruction inst)
     if (inst.Rc)
       ComputeRC0(gpr.GetImm(d));
   }
+  else if (gpr.IsImm(a, 0))
+  {
+    if (d != b)
+    {
+      gpr.BindToRegister(d, false);
+      MOV(gpr.R(d), gpr.R(b));
+    }
+    ComputeCarry(true);
+    if (inst.Rc)
+      ComputeRC0(gpr.R(d));
+  }
   else
   {
     gpr.BindToRegister(d, d == a || d == b);

From fc9f2d9cea4fc0e92e16edbe075780d68c591cc7 Mon Sep 17 00:00:00 2001
From: Sintendo <3380580+Sintendo@users.noreply.github.com>
Date: Wed, 6 Aug 2025 00:30:31 +0200
Subject: [PATCH 2/4] JitArm64_Integer: subfcx - Optimize b == 0

Equivalent to a negation, no need to materialize the zero.

Before:
0x52800015   mov    w21, #0x0                 ; =0
0x6b1802b6   subs   w22, w21, w24

After:
0x6b1803f6   negs   w22, w24
---
 Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
index 31b8f96f71e..25a4ada4780 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -1443,6 +1443,14 @@ void JitArm64::subfcx(UGeckoInstruction inst)
     if (inst.Rc)
       ComputeRC0(gpr.R(d));
   }
+  else if (gpr.IsImm(b, 0))
+  {
+    gpr.BindToRegister(d, d == a);
+    CARRY_IF_NEEDED(NEG, NEGS, gpr.R(d), gpr.R(a));
+    ComputeCarry();
+    if (inst.Rc)
+      ComputeRC0(gpr.R(d));
+  }
   else
   {
     gpr.BindToRegister(d, d == a || d == b);

From 45a3e35b0684d8f42e51f2c074e208658125b49e Mon Sep 17 00:00:00 2001
From: Sintendo <3380580+Sintendo@users.noreply.github.com>
Date: Wed, 6 Aug 2025 01:22:01 +0200
Subject: [PATCH 3/4] JitArm64_Integer: subfcx - Subtract 12-bit constant

Eliminate an instruction by encoding the constant in the subtraction.

Before:
0x5280037a   mov    w26, #0x1b                ; =27
0x6b1a02bb   subs   w27, w21, w26
0x93407f78   sxtw   x24, w27

After:
0x71006ebb   subs   w27, w21, #0x1b
0x93407f7a   sxtw   x26, w27
---
 Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
index 25a4ada4780..7cf2305d5a6 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -1443,6 +1443,14 @@ void JitArm64::subfcx(UGeckoInstruction inst)
     if (inst.Rc)
       ComputeRC0(gpr.R(d));
   }
+  else if (gpr.IsImm(a) && ((gpr.GetImm(a) & 0xFFF) == gpr.GetImm(a)))
+  {
+    gpr.BindToRegister(d, d == b);
+    CARRY_IF_NEEDED(SUB, SUBS, gpr.R(d), gpr.R(b), gpr.GetImm(a));
+    ComputeCarry();
+    if (inst.Rc)
+      ComputeRC0(gpr.R(d));
+  }
   else if (gpr.IsImm(b, 0))
   {
     gpr.BindToRegister(d, d == a);

From 6a92a90bce95641bf676a8214d80d2224b65ba83 Mon Sep 17 00:00:00 2001
From: Sintendo <3380580+Sintendo@users.noreply.github.com>
Date: Wed, 6 Aug 2025 01:27:35 +0200
Subject: [PATCH 4/4] JitArm64_Integer: subfcx - Subtract shifted 12-bit
 constant

Eliminate an instruction by encoding the constant in the subtraction,
part two.

Before:
0x52900019   mov    w25, #0x8000              ; =32768
0x6b190359   subs   w25, w26, w25

After:
0x71402359   subs   w25, w26, #0x8, lsl #12   ; =0x8000
---
 Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
index 7cf2305d5a6..3cf722409a8 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -1451,6 +1451,14 @@ void JitArm64::subfcx(UGeckoInstruction inst)
     if (inst.Rc)
       ComputeRC0(gpr.R(d));
   }
+  else if (gpr.IsImm(a) && ((gpr.GetImm(a) & 0xFFF000) == gpr.GetImm(a)))
+  {
+    gpr.BindToRegister(d, d == b);
+    CARRY_IF_NEEDED(SUB, SUBS, gpr.R(d), gpr.R(b), gpr.GetImm(a) >> 12, true);
+    ComputeCarry();
+    if (inst.Rc)
+      ComputeRC0(gpr.R(d));
+  }
   else if (gpr.IsImm(b, 0))
   {
     gpr.BindToRegister(d, d == a);