Hi Sterling,
I found that we can avoid emitting excessive literal loading
instructions with with section anchors.
This patch also passed the cases in testsuite/gcc.c-torture/execute/ dir.
Please apply it if OK for trunk.
Index: gcc/ChangeLog
===================================================================
--- gcc/ChangeLog (revision 206599)
+++ gcc/ChangeLog (working copy)
@@ -1,3 +1,11 @@
+2014-01-14 Felix Yang <fei.yang0...@gmail.com>
+
+ * common/config/xtensa/xtensa-common.c
+ (xtensa_option_optimization_table): Enable -fsection-anchors under -O1
+ or plus, and disable -fcommon by default.
+ * config/xtensa/xtensa.c (TARGET_MAX_ANCHOR_OFFSET): New.
+ (TARGET_MIN_ANCHOR_OFFSET): Ditto.
+
2014-01-14 Richard Biener <rguent...@suse.de>
PR tree-optimization/58921
Index: gcc/common/config/xtensa/xtensa-common.c
===================================================================
--- gcc/common/config/xtensa/xtensa-common.c (revision 206599)
+++ gcc/common/config/xtensa/xtensa-common.c (working copy)
@@ -35,6 +35,13 @@ static const struct default_options xtensa_option_
assembler, so GCC cannot do a good job of reordering blocks.
Do not enable reordering unless it is explicitly requested. */
{ OPT_LEVELS_ALL, OPT_freorder_blocks, NULL, 0 },
+ /* Enable section anchors under -O1 or plus. This can avoid generating
+ excessive literal loading instructions to load addresses of globals. */
+ { OPT_LEVELS_1_PLUS, OPT_fsection_anchors, NULL, 2 },
+ /* Allocate uninitialized global variables in the data section of object
+ file, rather than generating them as common blocks. This is required
+ for section anchors to work on uninitialized globals. */
+ { OPT_LEVELS_ALL, OPT_fcommon, NULL, 0 },
{ OPT_LEVELS_NONE, 0, NULL, 0 }
};
Index: gcc/config/xtensa/xtensa.c
===================================================================
--- gcc/config/xtensa/xtensa.c (revision 206599)
+++ gcc/config/xtensa/xtensa.c (working copy)
@@ -290,6 +290,12 @@ static const int reg_nonleaf_alloc_order[FIRST_PSE
#undef TARGET_CANNOT_FORCE_CONST_MEM
#define TARGET_CANNOT_FORCE_CONST_MEM xtensa_cannot_force_const_mem
+#undef TARGET_MAX_ANCHOR_OFFSET
+#define TARGET_MAX_ANCHOR_OFFSET 255
+
+#undef TARGET_MIN_ANCHOR_OFFSET
+#define TARGET_MIN_ANCHOR_OFFSET 0
+
#undef TARGET_LEGITIMATE_ADDRESS_P
#define TARGET_LEGITIMATE_ADDRESS_P xtensa_legitimate_address_p
Cheers,
Felix
