[PATCH v4 2/5] target/sparc: Populate sparc32 FQ when raising fp exception

[Richard Henderson <richard.henderson@linaro.org>]

From: Carl Hauser <chauser@pullman.com>

Implement a single instruction floating point queue,
populated while delivering an fp exception.

Signed-off-by: Carl Hauser <chauser@pullman.com>
[rth: Split from a larger patch]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/sparc/int32_helper.c | 40 +++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/target/sparc/int32_helper.c b/target/sparc/int32_helper.c
index 6b7d65b031..f2dd8bcb2e 100644
--- a/target/sparc/int32_helper.c
+++ b/target/sparc/int32_helper.c
@@ -21,10 +21,10 @@
 #include "qemu/main-loop.h"
 #include "cpu.h"
 #include "trace.h"
+#include "exec/cpu_ldst.h"
 #include "exec/log.h"
 #include "sysemu/runstate.h"
 
-
 static const char * const excp_names[0x80] = {
     [TT_TFAULT] = "Instruction Access Fault",
     [TT_ILL_INSN] = "Illegal Instruction",
@@ -116,22 +116,9 @@ void sparc_cpu_do_interrupt(CPUState *cs)
 
         qemu_log("%6d: %s (v=%02x)\n", count, name, intno);
         log_cpu_state(cs, 0);
-#if 0
-        {
-            int i;
-            uint8_t *ptr;
-
-            qemu_log("       code=");
-            ptr = (uint8_t *)env->pc;
-            for (i = 0; i < 16; i++) {
-                qemu_log(" %02x", ldub(ptr + i));
-            }
-            qemu_log("\n");
-        }
-#endif
         count++;
     }
-#if !defined(CONFIG_USER_ONLY)
+#ifndef CONFIG_USER_ONLY
     if (env->psret == 0) {
         if (cs->exception_index == 0x80 &&
             env->def.features & CPU_FEATURE_TA0_SHUTDOWN) {
@@ -143,6 +130,29 @@ void sparc_cpu_do_interrupt(CPUState *cs)
         }
         return;
     }
+    if (intno == TT_FP_EXCP) {
+        /*
+         * The sparc32 fpu has three states related to exception handling.
+         * The FPop that signals an exception transitions from fp_execute
+         * to fp_exception_pending.  A subsequent FPop transitions from
+         * fp_exception_pending to fp_exception, which forces the trap.
+         *
+         * If the queue is not empty, this trap is due to execution of an
+         * illegal FPop while in fp_exception state.  Here we are to
+         * re-enter fp_exception_pending state without queuing the insn.
+         *
+         * We do not model the fp_exception_pending state, but instead
+         * skip directly to fp_exception state.  We advance pc/npc to
+         * mimic delayed trap delivery as if by the subsequent insn.
+         */
+        if (!env->fsr_qne) {
+            env->fsr_qne = FSR_QNE;
+            env->fq.s.addr = env->pc;
+            env->fq.s.insn = cpu_ldl_code(env, env->pc);
+        }
+        env->pc = env->npc;
+        env->npc = env->npc + 4;
+    }
 #endif
     env->psret = 0;
     cwp = cpu_cwp_dec(env, env->cwp - 1);
-- 
2.43.0