It has come to my attention, by..ahem...you, that in handling the
testcase from my previous patch:
__transaction_relaxed { __asm__(""); }
...if we avoid instrumentation altogether, we shouldn't lie to the
run-time and pass PR_INSTRUMENTEDCODE.
I suppose we could cheat and avoid passing PR_INSTRUMENTEDCODE if we
ever enter expand_block_tm(), but perhaps we could do a little better as
with the attached patch.
With this patch, we generate:
tm_state.2_6 = __builtin__ITM_beginTransaction (16458); [
uninstrumentedCode hasNoAbort doesGoIrrevocable readOnly ]
Notice there is no "instrumentedCode".
By the way, can you double check my logic in expand_assign_tm() and
expand_call_tm(), particularly if we should bother setting
GTMA_INSTRUMENTED_CODE for thread private variables?
Thanks.
commit a441d916db334b71e76d9f4350ffdf992c058b4f
Author: Aldy Hernandez <al...@redhat.com>
Date: Thu Feb 21 16:02:11 2013 -0600
* trans-mem.c (expand_transaction): Only set PR_INSTRUMENTEDCODE
if there was instrumented code.
(expand_call_tm): Set GTMA_INSTRUMENTED_CODE.
(expand_assign_tm): Same.
* gimple.h (GTMA_INSTRUMENTED_CODE): New.
diff --git a/gcc/gimple.h b/gcc/gimple.h
index 4bd6b3d..baa5c24 100644
--- a/gcc/gimple.h
+++ b/gcc/gimple.h
@@ -661,6 +661,8 @@ struct GTY(()) gimple_statement_omp_atomic_store {
tell the runtime that it should begin the transaction in
serial-irrevocable mode. */
#define GTMA_DOES_GO_IRREVOCABLE (1u << 6)
+/* The transaction has at least one instrumented instruction within. */
+#define GTMA_INSTRUMENTED_CODE (1u << 7)
struct GTY(()) gimple_statement_transaction
{
diff --git a/gcc/testsuite/gcc.dg/tm/instrumented-mask.c
b/gcc/testsuite/gcc.dg/tm/instrumented-mask.c
new file mode 100644
index 0000000..6cfd3e4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tm/instrumented-mask.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-fgnu-tm -fdump-tree-tmmark" } */
+
+/* If we're sure to go irrevocable, as in the case below, do not pass
+ PR_INSTRUMENTEDCODE to the run-time if there is nothing
+ instrumented within the transaction. */
+
+int
+main()
+{
+ __transaction_relaxed { __asm__(""); }
+ return 0;
+}
+
+/* { dg-final { scan-tree-dump-times " instrumentedCode" 0 "tmmark" } } */
+/* { dg-final { cleanup-tree-dump "tmmark" } } */
diff --git a/gcc/trans-mem.c b/gcc/trans-mem.c
index 71eaa44..315f00c 100644
--- a/gcc/trans-mem.c
+++ b/gcc/trans-mem.c
@@ -2146,6 +2146,9 @@ expand_assign_tm (struct tm_region *region,
gimple_stmt_iterator *gsi)
{
/* Add thread private addresses to log if applicable. */
requires_barrier (region->entry_block, lhs, stmt);
+ // ?? Should we set GTMA_INSTRUMENTED_CODE here if there is no
+ // instrumentation, but requires_barrier added a thread private
+ // address to the log?
gsi_next (gsi);
return;
}
@@ -2153,6 +2156,8 @@ expand_assign_tm (struct tm_region *region,
gimple_stmt_iterator *gsi)
// Remove original load/store statement.
gsi_remove (gsi, true);
+ transaction_subcode_ior (region, GTMA_INSTRUMENTED_CODE);
+
if (load_p && !store_p)
{
transaction_subcode_ior (region, GTMA_HAVE_LOAD);
@@ -2230,9 +2235,12 @@ expand_call_tm (struct tm_region *region,
if (fn_decl == builtin_decl_explicit (BUILT_IN_TM_MEMCPY)
|| fn_decl == builtin_decl_explicit (BUILT_IN_TM_MEMMOVE))
- transaction_subcode_ior (region, GTMA_HAVE_STORE | GTMA_HAVE_LOAD);
+ transaction_subcode_ior (region, GTMA_HAVE_STORE
+ | GTMA_HAVE_LOAD
+ | GTMA_INSTRUMENTED_CODE);
if (fn_decl == builtin_decl_explicit (BUILT_IN_TM_MEMSET))
- transaction_subcode_ior (region, GTMA_HAVE_STORE);
+ transaction_subcode_ior (region, GTMA_HAVE_STORE
+ | GTMA_INSTRUMENTED_CODE);
if (is_tm_pure_call (stmt))
return false;
@@ -2243,7 +2251,8 @@ expand_call_tm (struct tm_region *region,
{
/* Assume all non-const/pure calls write to memory, except
transaction ending builtins. */
- transaction_subcode_ior (region, GTMA_HAVE_STORE);
+ transaction_subcode_ior (region, GTMA_HAVE_STORE
+ | GTMA_INSTRUMENTED_CODE);
}
/* For indirect calls, we already generated a call into the runtime. */
@@ -2602,7 +2611,7 @@ expand_transaction (struct tm_region *region, void *data
ATTRIBUTE_UNUSED)
flags |= PR_HASNOABORT;
if ((subcode & GTMA_HAVE_STORE) == 0)
flags |= PR_READONLY;
- if (inst_edge)
+ if (inst_edge && (subcode & GTMA_INSTRUMENTED_CODE))
flags |= PR_INSTRUMENTEDCODE;
if (uninst_edge)
flags |= PR_UNINSTRUMENTEDCODE;
