re PR target/49641 (Wrong code for ARMv4T and stmia)

2011-11-16  Richard Earnshaw  <rearnsha@arm.com>
	    Bernd Schmidt <bernds@coudesourcery.com>
	    Sebastian Huber <sebastian.huber@embedded-brains.de>

	PR target/49641
	* config/arm/arm.c (store_multiple_sequence): Avoid cases where
	the base reg is stored iff compiling for Thumb1.

	* gcc.target/arm/pr49641.c: New test.

Co-Authored-By: Bernd Schmidt <bernds@codesourcery.com>
Co-Authored-By: Sebastian Huber <sebastian.huber@embedded-brains.de>

From-SVN: r181416

gcc/ChangeLog

+2011-11-16  Richard Earnshaw  <rearnsha@arm.com>
+	    Bernd Schmidt <bernds@coudesourcery.com>
+	    Sebastian Huber <sebastian.huber@embedded-brains.de>
+
+	PR target/49641
+	* config/arm/arm.c (store_multiple_sequence): Avoid cases where
+	the base reg is stored iff compiling for Thumb1.
+
 2011-11-16  Razya Ladelsky  <razya@il.ibm.com>
 	
 	PR tree-optimization/49960

gcc/config/arm/arm.c

@@ -10247,6 +10247,9 @@ store_multiple_sequence (rtx *operands, int nops, int nops_total,
   rtx base_reg_rtx = NULL;
   int i, stm_case;
 
+  /* Write back of base register is currently only supported for Thumb 1.  */
+  int base_writeback = TARGET_THUMB1;
+
   /* Can only handle up to MAX_LDM_STM_OPS insns at present, though could be
      easily extended if required.  */
   gcc_assert (nops >= 2 && nops <= MAX_LDM_STM_OPS);
@@ -10304,7 +10307,9 @@ store_multiple_sequence (rtx *operands, int nops, int nops_total,
 	  /* If it isn't an integer register, then we can't do this.  */
 	  if (unsorted_regs[i] < 0
 	      || (TARGET_THUMB1 && unsorted_regs[i] > LAST_LO_REGNUM)
-	      || (TARGET_THUMB2 && unsorted_regs[i] == base_reg)
+	      /* The effects are unpredictable if the base register is
+		 both updated and stored.  */
+	      || (base_writeback && unsorted_regs[i] == base_reg)
 	      || (TARGET_THUMB2 && unsorted_regs[i] == SP_REGNUM)
 	      || unsorted_regs[i] > 14)
 	    return 0;

gcc/testsuite/ChangeLog

+2011-11-16  Richard Earnshaw  <rearnsha@arm.com>
+	    Bernd Schmidt <bernds@coudesourcery.com>
+	    Sebastian Huber <sebastian.huber@embedded-brains.de>
+
+	PR target/49641
+	* gcc.target/arm/pr49641.c: New test.
+
 2011-11-16  Razya Ladelsky  <razya@il.ibm.com>
 
         PR tree-optimization/49960

gcc/testsuite/gcc.target/arm/pr49641.c

+/* { dg-do compile } */
+/* { dg-options "-mthumb -O2" } */
+/* { dg-require-effective-target arm_thumb1_ok } */
+/* { dg-final { scan-assembler-not "stmia\[\\t \]*r3!\[^\\n]*r3" } } */
+typedef struct {
+  void *t1, *t2, *t3;
+} z;
+extern volatile int y;
+static inline void foo(z *x) {
+  x->t1 = &x->t2;
+  x->t2 = ((void *)0);
+  x->t3 = &x->t1;
+}
+extern z v;
+void bar (void) {
+   y = 0;
+   foo(&v);
+}