8319973: AArch64: Save and restore FPCR in the call stub

Reviewed-by: aph

Author: Boris Ulasevich

Diff for: src/hotspot/cpu/aarch64/assembler_aarch64.hpp

@@ -1088,8 +1088,8 @@ class Assembler : public AbstractAssembler {
 #undef INSN
 
   // we only provide mrs and msr for the special purpose system
-  // registers where op1 (instr[20:19]) == 11 and, (currently) only
-  // use it for FPSR n.b msr has L (instr[21]) == 0 mrs has L == 1
+  // registers where op1 (instr[20:19]) == 11
+  // n.b msr has L (instr[21]) == 0 mrs has L == 1
 
   void msr(int op1, int CRn, int CRm, int op2, Register rt) {
     starti;

Diff for: src/hotspot/cpu/aarch64/frame_aarch64.hpp

@@ -93,7 +93,7 @@
     // Entry frames
     // n.b. these values are determined by the layout defined in
     // stubGenerator for the Java call stub
-    entry_frame_after_call_words                     = 27,
+    entry_frame_after_call_words                     = 29,
     entry_frame_call_wrapper_offset                  = -8,
 
     // we don't need a save area

Diff for: src/hotspot/cpu/aarch64/macroAssembler_aarch64.hpp

@@ -570,6 +570,19 @@ class MacroAssembler: public Assembler {
     msr(0b011, 0b0100, 0b0100, 0b001, zr);
   }
 
+  // FPCR : op1 == 011
+  //        CRn == 0100
+  //        CRm == 0100
+  //        op2 == 000
+
+  inline void get_fpcr(Register reg) {
+    mrs(0b11, 0b0100, 0b0100, 0b000, reg);
+  }
+
+  inline void set_fpcr(Register reg) {
+    msr(0b011, 0b0100, 0b0100, 0b000, reg);
+  }
+
   // DCZID_EL0: op1 == 011
   //            CRn == 0000
   //            CRm == 0000

Diff for: src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp

@@ -136,7 +136,8 @@ class StubGenerator: public StubCodeGenerator {
   //     [ return_from_Java     ] <--- sp
   //     [ argument word n      ]
   //      ...
-  // -27 [ argument word 1      ]
+  // -29 [ argument word 1      ]
+  // -28 [ saved Floating-point Control Register ]
   // -26 [ saved v15            ] <--- sp_after_call
   // -25 [ saved v14            ]
   // -24 [ saved v13            ]
@@ -168,8 +169,9 @@ class StubGenerator: public StubCodeGenerator {
 
   // Call stub stack layout word offsets from fp
   enum call_stub_layout {
-    sp_after_call_off = -26,
+    sp_after_call_off  = -28,
 
+    fpcr_off           = sp_after_call_off,
     d15_off            = -26,
     d13_off            = -24,
     d11_off            = -22,
@@ -199,8 +201,9 @@ class StubGenerator: public StubCodeGenerator {
     StubCodeMark mark(this, "StubRoutines", "call_stub");
     address start = __ pc();
 
-    const Address sp_after_call(rfp, sp_after_call_off * wordSize);
+    const Address sp_after_call (rfp, sp_after_call_off * wordSize);
 
+    const Address fpcr_save     (rfp, fpcr_off           * wordSize);
     const Address call_wrapper  (rfp, call_wrapper_off   * wordSize);
     const Address result        (rfp, result_off         * wordSize);
     const Address result_type   (rfp, result_type_off    * wordSize);
@@ -249,6 +252,14 @@ class StubGenerator: public StubCodeGenerator {
     __ stpd(v13, v12,  d13_save);
     __ stpd(v15, v14,  d15_save);
 
+    __ get_fpcr(rscratch1);
+    __ str(rscratch1, fpcr_save);
+    // Set FPCR to the state we need. We do want Round to Nearest. We
+    // don't want non-IEEE rounding modes or floating-point traps.
+    __ bfi(rscratch1, zr, 22, 4); // Clear DN, FZ, and Rmode
+    __ bfi(rscratch1, zr, 8, 5);  // Clear exception-control bits (8-12)
+    __ set_fpcr(rscratch1);
+
     // install Java thread in global register now we have saved
     // whatever value it held
     __ mov(rthread, c_rarg7);
@@ -362,6 +373,10 @@ class StubGenerator: public StubCodeGenerator {
     __ ldp(r22, r21,   r22_save);
     __ ldp(r20, r19,   r20_save);
 
+    // restore fpcr
+    __ ldr(rscratch1,  fpcr_save);
+    __ set_fpcr(rscratch1);
+
     __ ldp(c_rarg0, c_rarg1,  call_wrapper);
     __ ldrw(c_rarg2, result_type);
     __ ldr(c_rarg3,  method);