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[patch,avr] PR78883: Implement CANNOT_CHANGE_MODE_CLASS.
- From: Georg-Johann Lay <avr at gjlay dot de>
- To: gcc-patches <gcc-patches at gcc dot gnu dot org>
- Cc: Denis Chertykov <chertykov at gmail dot com>, Segher Boessenkool <segher at kernel dot crashing dot org>, Dominik Vogt <vogt at linux dot vnet dot ibm dot com>
- Date: Mon, 2 Jan 2017 15:47:43 +0100
- Subject: [patch,avr] PR78883: Implement CANNOT_CHANGE_MODE_CLASS.
- Authentication-results: sourceware.org; auth=none
This fixes PR78883 which is a problem in reload revealed by a
change to combine.c. The fix is as proposed by Segher: implement
CANNOT_CHANGE_MODE_CLASS.
Ok for trunk?
Johann
gcc/
PR target/78883
* config/avr/avr.h (CANNOT_CHANGE_MODE_CLASS): New define.
* config/avr/avr-protos.h (avr_cannot_change_mode_class): New proto.
* config/avr/avr.c (avr_cannot_change_mode_class): New function.
gcc/testsuite/
PR target/78883
* gcc.c-torture/compile/pr78883.c: New test.
Index: config/avr/avr-protos.h
===================================================================
--- config/avr/avr-protos.h (revision 244001)
+++ config/avr/avr-protos.h (working copy)
@@ -111,7 +111,7 @@ extern int _reg_unused_after (rtx_insn *
extern int avr_jump_mode (rtx x, rtx_insn *insn);
extern int test_hard_reg_class (enum reg_class rclass, rtx x);
extern int jump_over_one_insn_p (rtx_insn *insn, rtx dest);
-
+extern int avr_cannot_change_mode_class (machine_mode, machine_mode, enum reg_class);
extern int avr_hard_regno_mode_ok (int regno, machine_mode mode);
extern void avr_final_prescan_insn (rtx_insn *insn, rtx *operand,
int num_operands);
Index: config/avr/avr.c
===================================================================
--- config/avr/avr.c (revision 244001)
+++ config/avr/avr.c (working copy)
@@ -11833,6 +11833,21 @@ jump_over_one_insn_p (rtx_insn *insn, rt
}
+/* Worker function for `CANNOT_CHANGE_MODE_CLASS'. */
+
+int
+avr_cannot_change_mode_class (machine_mode from, machine_mode to,
+ enum reg_class /* rclass */)
+{
+ /* We cannot access a hard register in a wider mode, for example we
+ must not access (reg:QI 31) as (reg:HI 31). HARD_REGNO_MODE_OK
+ would avoid such hard regs, but reload would generate it anyway
+ from paradoxical subregs of mem, cf. PR78883. */
+
+ return GET_MODE_SIZE (to) > GET_MODE_SIZE (from);
+}
+
+
/* Worker function for `HARD_REGNO_MODE_OK'. */
/* Returns 1 if a value of mode MODE can be stored starting with hard
register number REGNO. On the enhanced core, anything larger than
Index: config/avr/avr.h
===================================================================
--- config/avr/avr.h (revision 244001)
+++ config/avr/avr.h (working copy)
@@ -216,6 +216,9 @@ These two properties are reflected by bu
#define MODES_TIEABLE_P(MODE1, MODE2) 1
+#define CANNOT_CHANGE_MODE_CLASS(MFROM, MTO, RCLASS) \
+ avr_cannot_change_mode_class (MFROM, MTO, RCLASS)
+
enum reg_class {
NO_REGS,
R0_REG, /* r0 */
Index: testsuite/gcc.c-torture/compile/pr78883.c
===================================================================
--- testsuite/gcc.c-torture/compile/pr78883.c (nonexistent)
+++ testsuite/gcc.c-torture/compile/pr78883.c (working copy)
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+
+int foo (int *p)
+{
+ int i;
+ for (i = 0; i < 5; i++)
+ {
+ if (p[i] & 1)
+ return i;
+ }
+ return -1;
+}