From 344ee76aba63b0061058c60041dbd3ecaaf5125e Mon Sep 17 00:00:00 2001
From: MerryMage <MerryMage@users.noreply.github.com>
Date: Wed, 12 Sep 2018 14:03:46 +0100
Subject: [PATCH] emit_x64_floating_point: Hardware FMA implementation of
 FPRecipStepFused{32,64}

---
 src/backend/x64/emit_x64_floating_point.cpp | 44 +++++++++++++++++++--
 1 file changed, 41 insertions(+), 3 deletions(-)

diff --git a/src/backend/x64/emit_x64_floating_point.cpp b/src/backend/x64/emit_x64_floating_point.cpp
index f514d98b..329b492c 100644
--- a/src/backend/x64/emit_x64_floating_point.cpp
+++ b/src/backend/x64/emit_x64_floating_point.cpp
@@ -719,8 +719,46 @@ void EmitX64::EmitFPRecipEstimate64(EmitContext& ctx, IR::Inst* inst) {
     EmitFPRecipEstimate<u64>(code, ctx, inst);
 }
 
-template<typename FPT>
+template<size_t fsize>
 static void EmitFPRecipStepFused(BlockOfCode& code, EmitContext& ctx, IR::Inst* inst) {
+    using FPT = mp::unsigned_integer_of_size<fsize>;
+
+    if (code.DoesCpuSupport(Xbyak::util::Cpu::tFMA)) {
+        auto args = ctx.reg_alloc.GetArgumentInfo(inst);
+
+        Xbyak::Label end, fallback;
+
+        const Xbyak::Xmm operand1 = ctx.reg_alloc.UseXmm(args[0]);
+        const Xbyak::Xmm operand2 = ctx.reg_alloc.UseXmm(args[1]);
+        const Xbyak::Xmm result = ctx.reg_alloc.ScratchXmm();
+
+        code.movaps(result, code.MConst(xword, FP::FPValue<FPT, false, 0, 2>()));
+        FCODE(vfnmadd231s)(result, operand1, operand2);
+        FCODE(ucomis)(result, result);
+        code.jp(fallback, code.T_NEAR);
+        code.L(end);
+
+        code.SwitchToFarCode();
+        code.L(fallback);
+
+        code.sub(rsp, 8);
+        ABI_PushCallerSaveRegistersAndAdjustStackExcept(code, HostLocXmmIdx(result.getIdx()));
+        code.movq(code.ABI_PARAM1, operand1);
+        code.movq(code.ABI_PARAM2, operand2);
+        code.mov(code.ABI_PARAM3.cvt32(), ctx.FPCR());
+        code.lea(code.ABI_PARAM4, code.ptr[code.r15 + code.GetJitStateInfo().offsetof_fpsr_exc]);
+        code.CallFunction(&FP::FPRecipStepFused<FPT>);
+        code.movq(result, code.ABI_RETURN);
+        ABI_PopCallerSaveRegistersAndAdjustStackExcept(code, HostLocXmmIdx(result.getIdx()));
+        code.add(rsp, 8);
+
+        code.jmp(end, code.T_NEAR);
+        code.SwitchToNearCode();
+
+        ctx.reg_alloc.DefineValue(inst, result);
+        return;
+    }
+
     auto args = ctx.reg_alloc.GetArgumentInfo(inst);
     ctx.reg_alloc.HostCall(inst, args[0], args[1]);
     code.mov(code.ABI_PARAM3.cvt32(), ctx.FPCR());
@@ -729,11 +767,11 @@ static void EmitFPRecipStepFused(BlockOfCode& code, EmitContext& ctx, IR::Inst*
 }
 
 void EmitX64::EmitFPRecipStepFused32(EmitContext& ctx, IR::Inst* inst) {
-    EmitFPRecipStepFused<u32>(code, ctx, inst);
+    EmitFPRecipStepFused<32>(code, ctx, inst);
 }
 
 void EmitX64::EmitFPRecipStepFused64(EmitContext& ctx, IR::Inst* inst) {
-    EmitFPRecipStepFused<u64>(code, ctx, inst);
+    EmitFPRecipStepFused<64>(code, ctx, inst);
 }
 
 static void EmitFPRound(BlockOfCode& code, EmitContext& ctx, IR::Inst* inst, size_t fsize) {