From d877cfa4e2c3baf3cb8b8449d1608e1c2f05208c Mon Sep 17 00:00:00 2001 From: Sintendo <3380580+Sintendo@users.noreply.github.com> Date: Wed, 26 Jun 2024 00:07:20 +0200 Subject: [PATCH] JitArm64_Integer: Optimize subfic for zero When the immediate value is zero, we can do a negation. On ARM64 the NEG /NEGS instructions are just an alias for SUB/SUBS with a hardcoded WZR. Before: ``` ldr w22, [x29, #0x28] mov w21, #0x0 ; =0 subs w22, w21, w22 ``` After: ``` ldr w22, [x29, #0x28] negs w22, w22 ``` --- .../Core/PowerPC/JitArm64/JitArm64_Integer.cpp | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp index 7e5817ac0c..f3d263379c 100644 --- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp +++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp @@ -1392,13 +1392,19 @@ void JitArm64::subfic(UGeckoInstruction inst) } else { - const bool allocate_reg = d == a; - gpr.BindToRegister(d, allocate_reg); + const bool will_read = d == a; + const bool is_zero = imm == 0; + const bool allocate_reg = will_read && !is_zero; + gpr.BindToRegister(d, will_read); // d = imm - a ARM64Reg RD = gpr.R(d); - ARM64Reg WA = allocate_reg ? gpr.GetReg() : RD; - MOVI2R(WA, imm); + ARM64Reg WA = ARM64Reg::WZR; + if (!is_zero) + { + WA = will_read ? gpr.GetReg() : RD; + MOVI2R(WA, imm); + } CARRY_IF_NEEDED(SUB, SUBS, RD, WA, gpr.R(a)); if (allocate_reg)