8330094: RISC-V: Save and restore FRM in the call stub

Reviewed-by: fyang
Backport-of: b0496096dc8d7dc7acf28aa006141a3ecea446de

Author: zifeihan

src/hotspot/cpu/riscv/frame_riscv.hpp

@@ -131,7 +131,7 @@
     // Entry frames
     // n.b. these values are determined by the layout defined in
     // stubGenerator for the Java call stub
-    entry_frame_after_call_words                     =  34,
+    entry_frame_after_call_words                     =  35,
     entry_frame_call_wrapper_offset                  = -10,
 
     // we don't need a save area

src/hotspot/cpu/riscv/riscv_v.ad

@@ -3000,7 +3000,6 @@ instruct vloadcon(vReg dst, immI0 src) %{
     __ vsetvli_helper(bt, Matcher::vector_length(this));
     __ vid_v(as_VectorRegister($dst$$reg));
     if (is_floating_point_type(bt)) {
-      __ csrwi(CSR_FRM, C2_MacroAssembler::rne);
       __ vfcvt_f_x_v(as_VectorRegister($dst$$reg), as_VectorRegister($dst$$reg));
     }
   %}
@@ -3214,7 +3213,6 @@ instruct vcvtBtoX(vReg dst, vReg src) %{
     if (is_floating_point_type(bt)) {
       __ integer_extend_v(as_VectorRegister($dst$$reg), bt == T_FLOAT ? T_INT : T_LONG,
                           Matcher::vector_length(this), as_VectorRegister($src$$reg), T_BYTE);
-      __ csrwi(CSR_FRM, C2_MacroAssembler::rne);
       __ vfcvt_f_x_v(as_VectorRegister($dst$$reg), as_VectorRegister($dst$$reg));
     } else {
       __ integer_extend_v(as_VectorRegister($dst$$reg), bt, 
@@ -3261,7 +3259,6 @@ instruct vcvtStoX_fp_extend(vReg dst, vReg src) %{
     __ integer_extend_v(as_VectorRegister($dst$$reg), (bt == T_FLOAT ? T_INT : T_LONG),
                         Matcher::vector_length(this), as_VectorRegister($src$$reg), T_SHORT);
     __ vsetvli_helper(bt, Matcher::vector_length(this));
-    __ csrwi(CSR_FRM, C2_MacroAssembler::rne);
     __ vfcvt_f_x_v(as_VectorRegister($dst$$reg), as_VectorRegister($dst$$reg));
   %}
   ins_pipe(pipe_slow);
@@ -3300,7 +3297,6 @@ instruct vcvtItoF(vReg dst, vReg src) %{
   format %{ "vcvtItoF $dst, $src" %}
   ins_encode %{
     __ vsetvli_helper(T_FLOAT, Matcher::vector_length(this));
-    __ csrwi(CSR_FRM, C2_MacroAssembler::rne);
     __ vfcvt_f_x_v(as_VectorRegister($dst$$reg), as_VectorRegister($src$$reg));
   %}
   ins_pipe(pipe_slow);
@@ -3313,7 +3309,6 @@ instruct vcvtItoD(vReg dst, vReg src) %{
   format %{ "vcvtItoD $dst, $src" %}
   ins_encode %{
     __ vsetvli_helper(T_INT, Matcher::vector_length(this), Assembler::mf2);
-    __ csrwi(CSR_FRM, C2_MacroAssembler::rne);
     __ vfwcvt_f_x_v(as_VectorRegister($dst$$reg), as_VectorRegister($src$$reg));
   %}
   ins_pipe(pipe_slow);
@@ -3341,7 +3336,6 @@ instruct vcvtLtoF(vReg dst, vReg src) %{
   format %{ "vcvtLtoF $dst, $src" %}
   ins_encode %{
     __ vsetvli_helper(T_FLOAT, Matcher::vector_length(this), Assembler::mf2);
-    __ csrwi(CSR_FRM, C2_MacroAssembler::rne);
     __ vfncvt_f_x_w(as_VectorRegister($dst$$reg), as_VectorRegister($src$$reg));
   %}
   ins_pipe(pipe_slow);
@@ -3353,7 +3347,6 @@ instruct vcvtLtoD(vReg dst, vReg src) %{
   format %{ "vcvtLtoD $dst, $src" %}
   ins_encode %{
     __ vsetvli_helper(T_DOUBLE, Matcher::vector_length(this));
-    __ csrwi(CSR_FRM, C2_MacroAssembler::rne);
     __ vfcvt_f_x_v(as_VectorRegister($dst$$reg), as_VectorRegister($src$$reg));
   %}
   ins_pipe(pipe_slow);
@@ -3411,7 +3404,6 @@ instruct vcvtFtoD(vReg dst, vReg src) %{
   format %{ "vcvtFtoD $dst, $src" %}
   ins_encode %{
     __ vsetvli_helper(T_FLOAT, Matcher::vector_length(this), Assembler::mf2);
-    __ csrwi(CSR_FRM, C2_MacroAssembler::rne);
     __ vfwcvt_f_f_v(as_VectorRegister($dst$$reg), as_VectorRegister($src$$reg));
   %}
   ins_pipe(pipe_slow);
@@ -3459,7 +3451,6 @@ instruct vcvtDtoF(vReg dst, vReg src) %{
   format %{ "vcvtDtoF $dst, $src" %}
   ins_encode %{
     __ vsetvli_helper(T_FLOAT, Matcher::vector_length(this), Assembler::mf2);
-    __ csrwi(CSR_FRM, C2_MacroAssembler::rne);
     __ vfncvt_f_f_w(as_VectorRegister($dst$$reg), as_VectorRegister($src$$reg));
   %}
   ins_pipe(pipe_slow);

src/hotspot/cpu/riscv/stubGenerator_riscv.cpp

@@ -127,8 +127,9 @@ class StubGenerator: public StubCodeGenerator {
   //     [ return_from_Java     ] <--- sp
   //     [ argument word n      ]
   //      ...
-  // -34 [ argument word 1      ]
-  // -33 [ saved f27            ] <--- sp_after_call
+  // -35 [ argument word 1      ]
+  // -34 [ saved FRM in Floating-point Control and Status Register ] <--- sp_after_call
+  // -33 [ saved f27            ]
   // -32 [ saved f26            ]
   // -31 [ saved f25            ]
   // -30 [ saved f24            ]
@@ -165,8 +166,9 @@ class StubGenerator: public StubCodeGenerator {
 
   // Call stub stack layout word offsets from fp
   enum call_stub_layout {
-    sp_after_call_off  = -33,
+    sp_after_call_off  = -34,
 
+    frm_off            = sp_after_call_off,
     f27_off            = -33,
     f26_off            = -32,
     f25_off            = -31,
@@ -214,6 +216,7 @@ class StubGenerator: public StubCodeGenerator {
 
     const Address sp_after_call (fp, sp_after_call_off  * wordSize);
 
+    const Address frm_save      (fp, frm_off            * wordSize);
     const Address call_wrapper  (fp, call_wrapper_off   * wordSize);
     const Address result        (fp, result_off         * wordSize);
     const Address result_type   (fp, result_type_off    * wordSize);
@@ -296,6 +299,16 @@ class StubGenerator: public StubCodeGenerator {
     __ fsd(f26, f26_save);
     __ fsd(f27, f27_save);
 
+    __ frrm(t0);
+    __ sd(t0, frm_save);
+    // Set frm to the state we need. We do want Round to Nearest. We
+    // don't want non-IEEE rounding modes.
+    Label skip_fsrmi;
+    guarantee(__ RoundingMode::rne == 0, "must be");
+    __ beqz(t0, skip_fsrmi);
+    __ fsrmi(__ RoundingMode::rne);
+    __ bind(skip_fsrmi);
+
     // install Java thread in global register now we have saved
     // whatever value it held
     __ mv(xthread, c_rarg7);
@@ -415,6 +428,14 @@ class StubGenerator: public StubCodeGenerator {
 
     __ ld(x9, x9_save);
 
+    // restore frm
+    Label skip_fsrm;
+    __ ld(t0, frm_save);
+    __ frrm(t1);
+    __ beq(t0, t1, skip_fsrm);
+    __ fsrm(t0);
+    __ bind(skip_fsrm);
+
     __ ld(c_rarg0, call_wrapper);
     __ ld(c_rarg1, result);
     __ ld(c_rarg2, result_type);