[Guile-commits] 01/06: Allow jit_begin_data to declare max data size

[Andy Wingo]

wingo pushed a commit to branch master
in repository guile.

commit 44b07aef4b893af7057a4a25edea56a7c8346a79
Author: Andy Wingo <wingo@igalia.com>
AuthorDate: Thu Jul 30 13:36:24 2020 +0200

    Allow jit_begin_data to declare max data size
    
    * lightening.h:
    * lightening/lightening.c (jit_begin_data): Add max data size
      parameter.  If nonzero, can allow the JIT to avoid prematurely
      emitting a constant pool.
      (jit_end_data): Allow pending literals.
    * tests/jmp_table.c (run_test): Use new API.
---
 lightening.h            |  2 +-
 lightening/lightening.c | 16 ++++++++--------
 tests/jmp_table.c       |  2 +-
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/lightening.h b/lightening.h
index 020c479..efa5dfd 100644
--- a/lightening.h
+++ b/lightening.h
@@ -661,7 +661,7 @@ FOR_EACH_INSTRUCTION(DECLARE_INSTRUCTION)
 #  define jit_truncr_f(j,u,v)  jit_truncr_f_l(j,u,v)
 #endif
 
-void jit_begin_data(jit_state_t *);
+void jit_begin_data(jit_state_t *, size_t max_size_or_zero);
 void jit_end_data(jit_state_t *);
 void jit_emit_u8(jit_state_t *, uint8_t);
 void jit_emit_u16(jit_state_t *, uint16_t);
diff --git a/lightening/lightening.c b/lightening/lightening.c
index 775b2b6..97f4de0 100644
--- a/lightening/lightening.c
+++ b/lightening/lightening.c
@@ -484,12 +484,16 @@ jit_patch_there(jit_state_t* _jit, jit_reloc_t reloc, 
jit_pointer_t addr)
 }
 
 void
-jit_begin_data(jit_state_t *j)
+jit_begin_data(jit_state_t *j, size_t max_size_or_zero)
 {
 #ifdef JIT_NEEDS_LITERAL_POOL
-  if (j->pool->size)
-    emit_literal_pool(j, NO_GUARD_NEEDED);
-  ASSERT(j->overflow || j->pool->size == 0);
+  if (j->pool->size) {
+    uint8_t *deadline = j->start + j->pool->deadline;
+    // Emit a literal pool now if the data might overwrite the deadline.
+    // Emitting data won't add entries to the pool.
+    if (max_size_or_zero == 0 || j->pc.uc + max_size_or_zero >= deadline)
+      emit_literal_pool(j, NO_GUARD_NEEDED);
+  }
 #endif
 
   ASSERT(!j->emitting_data);
@@ -499,10 +503,6 @@ jit_begin_data(jit_state_t *j)
 void
 jit_end_data(jit_state_t *j)
 {
-#ifdef JIT_NEEDS_LITERAL_POOL
-  ASSERT(j->overflow || j->pool->size == 0);
-#endif
-
   ASSERT(j->emitting_data);
   j->emitting_data = 0;
 }
diff --git a/tests/jmp_table.c b/tests/jmp_table.c
index 6d86b65..f90ab16 100644
--- a/tests/jmp_table.c
+++ b/tests/jmp_table.c
@@ -17,7 +17,7 @@ run_test(jit_state_t *j, uint8_t *arena_base, size_t 
arena_size)
   jit_ldxr(j, JIT_R1, JIT_R1, JIT_R0);
   jit_jmpr(j, JIT_R1);
 
-  jit_begin_data (j);
+  jit_begin_data (j, (NTARGETS + 1) * sizeof(intptr_t));
   jit_align(j, sizeof(intptr_t));
   jit_patch_here(j, table);
   jit_reloc_t targets[NTARGETS];