From 04c1a0d2de23338a3f674addcbf667d365118df6 Mon Sep 17 00:00:00 2001
From: MerryMage <MerryMage@users.noreply.github.com>
Date: Sun, 7 Aug 2016 22:47:17 +0100
Subject: [PATCH] EmitX64: Switch MXCSR when switching to interpreter

---
 src/backend_x64/block_of_code.cpp | 18 +++++++++++++-----
 src/backend_x64/block_of_code.h   |  5 ++++-
 src/backend_x64/emit_x64.cpp      |  9 ++++-----
 3 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/src/backend_x64/block_of_code.cpp b/src/backend_x64/block_of_code.cpp
index d19a8d6c..78b66129 100644
--- a/src/backend_x64/block_of_code.cpp
+++ b/src/backend_x64/block_of_code.cpp
@@ -40,11 +40,11 @@ size_t BlockOfCode::RunCode(JitState* jit_state, CodePtr basic_block, size_t cyc
     return cycles_to_run - jit_state->cycles_remaining; // Return number of cycles actually run.
 }
 
-void BlockOfCode::ReturnFromRunCode() {
-    STMXCSR(MDisp(R15, offsetof(JitState, guest_MXCSR)));
-    LDMXCSR(MDisp(R15, offsetof(JitState, save_host_MXCSR)));
-    MOV(64, R(RSP), MDisp(R15, offsetof(JitState, save_host_RSP)));
+void BlockOfCode::ReturnFromRunCode(bool MXCSR_switch) {
+    if (MXCSR_switch)
+        SwitchMxcsrOnExit();
 
+    MOV(64, R(RSP), MDisp(R15, offsetof(JitState, save_host_RSP)));
     ABI_PopRegistersAndAdjustStack(ABI_ALL_CALLEE_SAVED, 8);
     RET();
 }
@@ -78,10 +78,18 @@ void BlockOfCode::GenRunCode() {
 
     MOV(64, R(R15), R(ABI_PARAM1));
     MOV(64, MDisp(R15, offsetof(JitState, save_host_RSP)), R(RSP));
+    SwitchMxcsrOnEntry();
+    JMPptr(R(ABI_PARAM2));
+}
+
+void BlockOfCode::SwitchMxcsrOnEntry() {
     STMXCSR(MDisp(R15, offsetof(JitState, save_host_MXCSR)));
     LDMXCSR(MDisp(R15, offsetof(JitState, guest_MXCSR)));
+}
 
-    JMPptr(R(ABI_PARAM2));
+void BlockOfCode::SwitchMxcsrOnExit() {
+    STMXCSR(MDisp(R15, offsetof(JitState, guest_MXCSR)));
+    LDMXCSR(MDisp(R15, offsetof(JitState, save_host_MXCSR)));
 }
 
 } // namespace BackendX64
diff --git a/src/backend_x64/block_of_code.h b/src/backend_x64/block_of_code.h
index a145b65d..e916de36 100644
--- a/src/backend_x64/block_of_code.h
+++ b/src/backend_x64/block_of_code.h
@@ -20,7 +20,10 @@ public:
     void ClearCache(bool poison_memory);
 
     size_t RunCode(JitState* jit_state, CodePtr basic_block, size_t cycles_to_run) const;
-    void ReturnFromRunCode();
+    void ReturnFromRunCode(bool MXCSR_switch = true);
+
+    void SwitchMxcsrOnEntry();
+    void SwitchMxcsrOnExit();
 
     Gen::OpArg MFloatNegativeZero32() const {
         return Gen::M(const_FloatNegativeZero32);
diff --git a/src/backend_x64/emit_x64.cpp b/src/backend_x64/emit_x64.cpp
index 21dbe5af..64f7859c 100644
--- a/src/backend_x64/emit_x64.cpp
+++ b/src/backend_x64/emit_x64.cpp
@@ -308,11 +308,9 @@ void EmitX64::EmitCallSupervisor(IR::Block&, IR::Inst* inst) {
 
     reg_alloc.HostCall(nullptr, imm32);
 
-    code->STMXCSR(MDisp(R15, offsetof(JitState, guest_MXCSR)));
-    code->LDMXCSR(MDisp(R15, offsetof(JitState, save_host_MXCSR)));
+    code->SwitchMxcsrOnExit();
     code->ABI_CallFunction(reinterpret_cast<void*>(cb.CallSVC));
-    code->STMXCSR(MDisp(R15, offsetof(JitState, save_host_MXCSR)));
-    code->LDMXCSR(MDisp(R15, offsetof(JitState, guest_MXCSR)));
+    code->SwitchMxcsrOnEntry();
 }
 
 void EmitX64::EmitGetCarryFromOp(IR::Block&, IR::Inst*) {
@@ -1514,8 +1512,9 @@ void EmitX64::EmitTerminalInterpret(IR::Term::Interpret terminal, Arm::LocationD
     code->MOV(64, R(ABI_PARAM2), Imm64(reinterpret_cast<u64>(jit_interface)));
     code->MOV(32, MJitStateReg(Arm::Reg::PC), R(ABI_PARAM1));
     code->MOV(64, R(RSP), MDisp(R15, offsetof(JitState, save_host_RSP)));
+    code->SwitchMxcsrOnExit();
     code->ABI_CallFunction(reinterpret_cast<void*>(cb.InterpreterFallback));
-    code->ReturnFromRunCode(); // TODO: Check cycles
+    code->ReturnFromRunCode(false); // TODO: Check cycles
 }
 
 void EmitX64::EmitTerminalReturnToDispatch(IR::Term::ReturnToDispatch, Arm::LocationDescriptor initial_location) {