target/ppc: Increment PMC5 with inline insns

Profiling QEMU during Fedora 35 for PPC64 boot revealed that
6.39% of total time was being spent in helper_insns_inc(), on a
POWER9 machine. To avoid calling this helper every time PMCs had
to be incremented, an inline implementation of PMC5 increment and
check for overflow was developed. This led to a reduction of
about 12% in Fedora's boot time.

Signed-off-by: Leandro Lupori <leandro.lupori@eldorado.org.br>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20221025202424.195984-4-leandro.lupori@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

1 files changed, 25 insertions, 3 deletions

diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 8d79522..19c1d17 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -36,6 +36,7 @@
 #include "exec/log.h"
 #include "qemu/atomic128.h"
 #include "spr_common.h"
+#include "power8-pmu.h"
 
 #include "qemu/qemu-print.h"
 #include "qapi/error.h"
@@ -4271,6 +4272,9 @@ static void pmu_count_insns(DisasContext *ctx)
     }
 
  #if !defined(CONFIG_USER_ONLY)
+    TCGLabel *l;
+    TCGv t0;
+
     /*
      * The PMU insns_inc() helper stops the internal PMU timer if a
      * counter overflows happens. In that case, if the guest is
@@ -4279,8 +4283,26 @@ static void pmu_count_insns(DisasContext *ctx)
      */
     gen_icount_io_start(ctx);
 
-    gen_helper_insns_inc(cpu_env, tcg_constant_i32(ctx->base.num_insns));
-#else
+    /* Avoid helper calls when only PMC5-6 are enabled. */
+    if (!ctx->pmc_other) {
+        l = gen_new_label();
+        t0 = tcg_temp_new();
+
+        gen_load_spr(t0, SPR_POWER_PMC5);
+        tcg_gen_addi_tl(t0, t0, ctx->base.num_insns);
+        gen_store_spr(SPR_POWER_PMC5, t0);
+        /* Check for overflow, if it's enabled */
+        if (ctx->mmcr0_pmcjce) {
+            tcg_gen_brcondi_tl(TCG_COND_LT, t0, PMC_COUNTER_NEGATIVE_VAL, l);
+            gen_helper_handle_pmc5_overflow(cpu_env);
+        }
+
+        gen_set_label(l);
+        tcg_temp_free(t0);
+    } else {
+        gen_helper_insns_inc(cpu_env, tcg_constant_i32(ctx->base.num_insns));
+    }
+  #else
     /*
      * User mode can read (but not write) PMC5 and start/stop
      * the PMU via MMCR0_FC. In this case just increment
@@ -4293,7 +4315,7 @@ static void pmu_count_insns(DisasContext *ctx)
     gen_store_spr(SPR_POWER_PMC5, t0);
 
     tcg_temp_free(t0);
-#endif /* #if !defined(CONFIG_USER_ONLY) */
+  #endif /* #if !defined(CONFIG_USER_ONLY) */
 }
 #else
 static void pmu_count_insns(DisasContext *ctx)