The following avoids to increase hard register lifetime by not
sinking loads from those.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
I wonder if it would make sense to not treat hardregs as
memory but instead rewrite them into SSA form but with
SSA_NAME_OCCURS_IN_ABNORMAL_PHI set (which really tells
that all SSA names of the underlying decl must be able
to coalesce to the same register).
Richard.
2014-06-24 Richard Biener <rguent...@suse.de>
PR tree-optimization/61572
* tree-ssa-sink.c (statement_sink_location): Do not sink
loads from hard registers.
* gcc.target/i386/pr61572.c: New testcase.
Index: gcc/tree-ssa-sink.c
===================================================================
--- gcc/tree-ssa-sink.c (revision 211928)
+++ gcc/tree-ssa-sink.c (working copy)
@@ -374,6 +374,12 @@ statement_sink_location (gimple stmt, ba
nearest to commondom. */
if (gimple_vuse (stmt))
{
+ /* Do not sink loads from hard registers. */
+ if (gimple_assign_single_p (stmt)
+ && TREE_CODE (gimple_assign_rhs1 (stmt)) == VAR_DECL
+ && DECL_HARD_REGISTER (gimple_assign_rhs1 (stmt)))
+ return false;
+
imm_use_iterator imm_iter;
use_operand_p use_p;
basic_block found = NULL;
Index: gcc/testsuite/gcc.target/i386/pr61572.c
===================================================================
--- gcc/testsuite/gcc.target/i386/pr61572.c (revision 0)
+++ gcc/testsuite/gcc.target/i386/pr61572.c (working copy)
@@ -0,0 +1,46 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+struct autofs_sb_info
+{
+ int exp_timeout;
+};
+void *f;
+int g;
+static int fn1 (struct autofs_sb_info *p1)
+{
+ int a, b;
+ a = (
+ {
+ register __typeof__(0) c
+#if defined __x86_64__
+ asm("rdx")
+#endif
+ ;
+ b = c;
+ int d;
+ __typeof__(0) e;
+ e = p1->exp_timeout / 1000;
+ switch (0)
+ default:
+ asm("" : "=a"(d) : "0"(e), ""(0));
+ d;
+ });
+ if (a)
+ return 1;
+ if (b)
+ p1->exp_timeout = 0;
+ return 0;
+}
+
+int fn2 ()
+{
+ struct autofs_sb_info *h = f;
+ switch (g)
+ {
+ case 0 ?:
+0 : return fn1 (h);
+ default:
+ return 0;
+ }
+}
