Hexagon (target/hexagon) put writes to USR into temp until commit

Change SET_USR_FIELD to write to hex_new_value[HEX_REG_USR] instead
of hex_gpr[HEX_REG_USR].

Then, we need code to mark the instructions that can set implicitly
set USR
- Macros added to hex_common.py
- A_FPOP added in translate.c

Test case added in tests/tcg/hexagon/overflow.c

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>

target/hexagon/attribs_def.h.inc

@@ -64,6 +64,7 @@ DEF_ATTRIB(IMPLICIT_WRITES_P1, "Writes Predicate 1", "", "UREG.P1")
 DEF_ATTRIB(IMPLICIT_WRITES_P2, "Writes Predicate 1", "", "UREG.P2")
 DEF_ATTRIB(IMPLICIT_WRITES_P3, "May write Predicate 3", "", "UREG.P3")
 DEF_ATTRIB(IMPLICIT_READS_PC, "Reads the PC register", "", "")
+DEF_ATTRIB(IMPLICIT_WRITES_USR, "May write USR", "", "")
 DEF_ATTRIB(WRITES_PRED_REG, "Writes a predicate register", "", "")
 
 DEF_ATTRIB(CRSLOT23, "Can execute in slot 2 or slot 3 (CR)", "", "")

target/hexagon/hex_common.py

@@ -73,6 +73,8 @@ def calculate_attribs():
     add_qemu_macro_attrib('fWRITE_P1', 'A_WRITES_PRED_REG')
     add_qemu_macro_attrib('fWRITE_P2', 'A_WRITES_PRED_REG')
     add_qemu_macro_attrib('fWRITE_P3', 'A_WRITES_PRED_REG')
+    add_qemu_macro_attrib('fSET_OVERFLOW', 'A_IMPLICIT_WRITES_USR')
+    add_qemu_macro_attrib('fSET_LPCFG', 'A_IMPLICIT_WRITES_USR')
 
     # Recurse down macros, find attributes from sub-macros
     macroValues = list(macros.values())

target/hexagon/macros.h

@@ -62,7 +62,7 @@
                    reg_field_info[FIELD].offset)
 
 #define SET_USR_FIELD(FIELD, VAL) \
-    fINSERT_BITS(env->gpr[HEX_REG_USR], reg_field_info[FIELD].width, \
+    fINSERT_BITS(env->new_value[HEX_REG_USR], reg_field_info[FIELD].width, \
                  reg_field_info[FIELD].offset, (VAL))
 #endif
 

target/hexagon/translate.c

@@ -204,7 +204,12 @@ static void mark_implicit_reg_write(DisasContext *ctx, Insn *insn,
                                     int attrib, int rnum)
 {
     if (GET_ATTRIB(insn->opcode, attrib)) {
-        bool is_predicated = GET_ATTRIB(insn->opcode, A_CONDEXEC);
+        /*
+         * USR is used to set overflow and FP exceptions,
+         * so treat it as conditional
+         */
+        bool is_predicated = GET_ATTRIB(insn->opcode, A_CONDEXEC) ||
+                             rnum == HEX_REG_USR;
         if (is_predicated && !is_preloaded(ctx, rnum)) {
             tcg_gen_mov_tl(hex_new_value[rnum], hex_gpr[rnum]);
         }
@@ -230,6 +235,8 @@ static void mark_implicit_reg_writes(DisasContext *ctx, Insn *insn)
     mark_implicit_reg_write(ctx, insn, A_IMPLICIT_WRITES_SA0, HEX_REG_SA0);
     mark_implicit_reg_write(ctx, insn, A_IMPLICIT_WRITES_LC1, HEX_REG_LC1);
     mark_implicit_reg_write(ctx, insn, A_IMPLICIT_WRITES_SA1, HEX_REG_SA1);
+    mark_implicit_reg_write(ctx, insn, A_IMPLICIT_WRITES_USR, HEX_REG_USR);
+    mark_implicit_reg_write(ctx, insn, A_FPOP, HEX_REG_USR);
 }
 
 static void mark_implicit_pred_writes(DisasContext *ctx, Insn *insn)

tests/tcg/hexagon/Makefile.target

@@ -40,5 +40,6 @@ HEX_TESTS += load_unpack
 HEX_TESTS += load_align
 HEX_TESTS += atomics
 HEX_TESTS += fpstuff
+HEX_TESTS += overflow
 
 TESTS += $(HEX_TESTS)

tests/tcg/hexagon/overflow.c

@@ -0,0 +1,107 @@
+/*
+ *  Copyright(c) 2021 Qualcomm Innovation Center, Inc. All Rights Reserved.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <setjmp.h>
+#include <signal.h>
+
+
+int err;
+
+static void __check(const char *filename, int line, int x, int expect)
+{
+    if (x != expect) {
+        printf("ERROR %s:%d - %d != %d\n",
+               filename, line, x, expect);
+        err++;
+    }
+}
+
+#define check(x, expect) __check(__FILE__, __LINE__, (x), (expect))
+
+static int satub(int src, int *p, int *ovf_result)
+{
+    int result;
+    int usr;
+
+    /*
+     * This instruction can set bit 0 (OVF/overflow) in usr
+     * Clear the bit first, then return that bit to the caller
+     *
+     * We also store the src into *p in the same packet, so we
+     * can ensure the overflow doesn't get set when an exception
+     * is generated.
+     */
+    asm volatile("r2 = usr\n\t"
+                 "r2 = clrbit(r2, #0)\n\t"        /* clear overflow bit */
+                 "usr = r2\n\t"
+                 "{\n\t"
+                 "    %0 = satub(%2)\n\t"
+                 "    memw(%3) = %2\n\t"
+                 "}\n\t"
+                 "%1 = usr\n\t"
+                 : "=r"(result), "=r"(usr)
+                 : "r"(src), "r"(p)
+                 : "r2", "usr", "memory");
+  *ovf_result = (usr & 1);
+  return result;
+}
+
+int read_usr_overflow(void)
+{
+    int result;
+    asm volatile("%0 = usr\n\t" : "=r"(result));
+    return result & 1;
+}
+
+
+jmp_buf jmp_env;
+int usr_overflow;
+
+static void sig_segv(int sig, siginfo_t *info, void *puc)
+{
+    usr_overflow = read_usr_overflow();
+    longjmp(jmp_env, 1);
+}
+
+int main()
+{
+    struct sigaction act;
+    int ovf;
+
+    /* SIGSEGV test */
+    act.sa_sigaction = sig_segv;
+    sigemptyset(&act.sa_mask);
+    act.sa_flags = SA_SIGINFO;
+    sigaction(SIGSEGV, &act, NULL);
+    if (setjmp(jmp_env) == 0) {
+        satub(300, 0, &ovf);
+    }
+
+    act.sa_handler = SIG_DFL;
+    sigemptyset(&act.sa_mask);
+    act.sa_flags = 0;
+
+    check(usr_overflow, 0);
+
+    puts(err ? "FAIL" : "PASS");
+    return err ? EXIT_FAILURE : EXIT_SUCCESS;
+}