[ARM] Fix Thumb-1 ldm (PR89190)

This patch fixes an ICE in the Thumb-1 LDM peepholer.  Thumb-1 LDMs
always update the base register except if the base is loaded.
The current implementation rejects LDMs where the base is not dead,
however this doesn't exclude the case where the base is loaded as
well as dead.  Fix this by explicitly checking whether the base is
loaded.  Also enable LDMs which load the first register.

    gcc/
	PR target/89190
	* config/arm/arm.c (ldm_stm_operation_p) Set
	addr_reg_in_reglist correctly for first register.
	(load_multiple_sequence): Remove dead base check.
	(gen_ldm_seq): Correctly set write_back for Thumb-1.

    testsuite/
	PR target/89190
	* gcc.target/arm/pr89190.c: New test.

From-SVN: r268848

gcc/ChangeLog

+2019-02-13  Wilco Dijkstra  <wdijkstr@arm.com>
+
+	PR target/89190
+	* config/arm/arm.c (ldm_stm_operation_p) Set
+	addr_reg_in_reglist correctly for first register.
+	(load_multiple_sequence): Remove dead base check.
+	(gen_ldm_seq): Correctly set write_back for Thumb-1.
+
 2019-02-13  Tamar Christina  <tamar.christina@arm.com>
 
 	PR target/88847

gcc/config/arm/arm.c

@@ -13191,6 +13191,9 @@ ldm_stm_operation_p (rtx op, bool load, machine_mode mode,
   if (load && (REGNO (reg) == SP_REGNUM) && (REGNO (addr) != SP_REGNUM))
     return false;
 
+  if (regno == REGNO (addr))
+    addr_reg_in_reglist = true;
+
   for (; i < count; i++)
     {
       elt = XVECEXP (op, 0, i);
@@ -13385,7 +13388,6 @@ load_multiple_sequence (rtx *operands, int nops, int *regs, int *saved_order,
   int unsorted_regs[MAX_LDM_STM_OPS];
   HOST_WIDE_INT unsorted_offsets[MAX_LDM_STM_OPS];
   int order[MAX_LDM_STM_OPS];
-  rtx base_reg_rtx = NULL;
   int base_reg = -1;
   int i, ldm_case;
 
@@ -13430,7 +13432,6 @@ load_multiple_sequence (rtx *operands, int nops, int *regs, int *saved_order,
 	  if (i == 0)
 	    {
 	      base_reg = REGNO (reg);
-	      base_reg_rtx = reg;
 	      if (TARGET_THUMB1 && base_reg > LAST_LO_REGNUM)
 		return 0;
 	    }
@@ -13489,10 +13490,6 @@ load_multiple_sequence (rtx *operands, int nops, int *regs, int *saved_order,
       *load_offset = unsorted_offsets[order[0]];
     }
 
-  if (TARGET_THUMB1
-      && !peep2_reg_dead_p (nops, base_reg_rtx))
-    return 0;
-
   if (unsorted_offsets[order[0]] == 0)
     ldm_case = 1; /* ldmia */
   else if (TARGET_ARM && unsorted_offsets[order[0]] == 4)
@@ -13868,9 +13865,17 @@ gen_ldm_seq (rtx *operands, int nops, bool sort_regs)
 
   if (TARGET_THUMB1)
     {
-      gcc_assert (peep2_reg_dead_p (nops, base_reg_rtx));
       gcc_assert (ldm_case == 1 || ldm_case == 5);
-      write_back = TRUE;
+
+      /* Thumb-1 ldm uses writeback except if the base is loaded.  */
+      write_back = true;
+      for (i = 0; i < nops; i++)
+	if (base_reg == regs[i])
+	  write_back = false;
+
+      /* Ensure the base is dead if it is updated.  */
+      if (write_back && !peep2_reg_dead_p (nops, base_reg_rtx))
+	return false;
     }
 
   if (ldm_case == 5)
@@ -13878,8 +13883,7 @@ gen_ldm_seq (rtx *operands, int nops, bool sort_regs)
       rtx newbase = TARGET_THUMB1 ? base_reg_rtx : gen_rtx_REG (SImode, regs[0]);
       emit_insn (gen_addsi3 (newbase, base_reg_rtx, GEN_INT (offset)));
       offset = 0;
-      if (!TARGET_THUMB1)
-	base_reg_rtx = newbase;
+      base_reg_rtx = newbase;
     }
 
   for (i = 0; i < nops; i++)

gcc/testsuite/ChangeLog

+2019-02-13  Wilco Dijkstra  <wdijkstr@arm.com>
+
+	PR target/89190
+	* gcc.target/arm/pr89190.c: New test.
+
 2019-02-13  David Malcolm  <dmalcolm@redhat.com>
 
 	PR c++/89036