[Guile-commits] 303/437: Only mark callee save regs as live on jumps that cannot be tracked.

[Andy Wingo]

wingo pushed a commit to branch lightning
in repository guile.

commit 45c4df506c31a38be1a18d76dac0a8d12fd9d423
Author: pcpa <address@hidden>
Date:   Mon Sep 1 16:27:19 2014 -0300

    Only mark callee save regs as live on jumps that cannot be tracked.
    
        * lib/lightning.c: Do not mark all registers in unknown state
        as live on jit_jmpr, or jit_jmpi to an absolute address. Instead,
        treat it as a function call, and only consider JIT_Vn registers
        as possibly live.
---
 ChangeLog       |  7 +++++++
 lib/lightning.c | 27 +++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index 1c88395..97c8f47 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2014-09-01 Paulo Andrade <address@hidden>
+
+       * lib/lightning.c: Do not mark all registers in unknown state
+       as live on jit_jmpr, or jit_jmpi to an absolute address. Instead,
+       treat it as a function call, and only consider JIT_Vn registers
+       as possibly live.
+
 2014-08-29 Paulo Andrade <address@hidden>
 
        * doc/body.texi: Add a proper info menu entry for
diff --git a/lib/lightning.c b/lib/lightning.c
index d816a45..a8a9463 100644
--- a/lib/lightning.c
+++ b/lib/lightning.c
@@ -2006,6 +2006,7 @@ _jit_update(jit_state_t *_jit, jit_node_t *node,
            jit_regset_t *live, jit_regset_t *mask)
 {
     jit_int32_t                 spec;
+    jit_int32_t                 regno;
     jit_regset_t        ztmp;
     jit_regset_t        zmask;
     unsigned long       value;
@@ -2165,6 +2166,32 @@ _jit_update(jit_state_t *_jit, jit_node_t *node,
                        }
                        continue;
                    }
+                   /* Should not really mark as live all registers in unknown
+                    * state if using jit_jmpr(), or jit_jmpi(absolute_address)
+                    * because that would leave the register allocator with
+                    * no options for "nospill" temporaries (other temporaries
+                    * also benefit from not needing to spill/reload), so, the
+                    * user must ensure to either spill/reload, or only leave
+                    * live registers on JIT_Vn if using a jump that cannot
+                    * be tracked around the generated jit code */
+                   for (spec = JIT_R_NUM - 1; spec >= 0; spec--) {
+                       regno = jit_r(spec);
+                       if (jit_regset_tstbit(mask, regno))
+                           jit_regset_clrbit(mask, regno);
+                   }
+                   for (spec = JIT_F_NUM - 1; spec >= 0; spec--) {
+                       regno = jit_f(spec);
+                       if (jit_regset_tstbit(mask, regno))
+                           jit_regset_clrbit(mask, regno);
+                   }
+                   /* In some backends JIT_Rn and JIT_Fn are callee save */
+                   for (regno = 0; regno < _jitc->reglen; regno++) {
+                       spec = jit_class(_rvs[regno].spec);
+                       if (jit_regset_tstbit(mask, regno) &&
+                           (spec & (jit_class_gpr|jit_class_fpr)) &&
+                           !(spec & jit_class_sav))
+                           jit_regset_clrbit(mask, regno);
+                   }
                    /* assume value is live due to jump to unknown location */
                    jit_regset_ior(live, live, mask);
                    jit_regset_set_ui(mask, 0);