Sometimes people write loops that they do not want optimized away, even
when the compiler can replace those loops by a simple expression (or
nothing). For such people, this patch adds a compiler option.
Bootstrapped on powerpc64-linux; regression check still in progress
(with Init(1) to actually test anything).
Segher
2016-04-01 Segher Boessenkool <seg...@kernel.crashing.org>
* loop-init.c: Include some more stuff that really doesn't belong
here, oh well.
(loop_optimizer_init): Add empty asm statements in all gimple loops,
if asked to.
* common.opt: Add new option.
---
gcc/common.opt | 4 ++++
gcc/loop-init.c | 15 +++++++++++++++
2 files changed, 19 insertions(+)
diff --git a/gcc/loop-init.c b/gcc/loop-init.c
index 8634591..7c5dc24 100644
--- a/gcc/loop-init.c
+++ b/gcc/loop-init.c
@@ -24,6 +24,8 @@ along with GCC; see the file COPYING3. If not see
#include "target.h"
#include "rtl.h"
#include "tree.h"
+#include "gimple.h"
+#include "gimple-iterator.h"
#include "cfghooks.h"
#include "df.h"
#include "regs.h"
@@ -91,6 +93,19 @@ loop_optimizer_init (unsigned flags)
/* Find the loops. */
current_loops = flow_loops_find (NULL);
+
+ if (flag_never_gonna_give_you_up && current_ir_type () == IR_GIMPLE)
+ {
+ struct loop *loop;
+ FOR_EACH_LOOP (loop, 0)
+ if (loop->latch)
+ {
+ gasm *p = gimple_build_asm_vec ("", 0, 0, 0, 0);
+ gimple_asm_set_volatile (p, true);
+ gimple_stmt_iterator bsi = gsi_after_labels (loop->latch);
+ gsi_insert_before (&bsi, p, GSI_SAME_STMT);
+ }
+ }
}
else
{
diff --git a/gcc/common.opt b/gcc/common.opt
index 0f3bb4e..b7c0a6a 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2002,6 +2002,10 @@ frerun-loop-opt
Common Ignore
Does nothing. Preserved for backward compatibility.
+frickroll-all-loops
+Common Report Var(flag_never_gonna_give_you_up) Init(0) Optimization
+You know the rules, and so do I.
+
frounding-math
Common Report Var(flag_rounding_math) Optimization SetByCombined
Disable optimizations that assume default FP rounding behavior.
--
1.9.3
