arm.c (MAX_INSN_PER_IT_BLOCK): New macro.

2013-06-05  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

	* config/arm/arm.c (MAX_INSN_PER_IT_BLOCK): New macro.
	(arm_option_override): Override arm_restrict_it where appropriate.
	(thumb2_final_prescan_insn): Use MAX_INSN_PER_IT_BLOCK.
	* config/arm/arm.opt (mrestrict-it): New command-line option.
	* doc/invoke.texi: Document -mrestrict-it.

From-SVN: r199694

gcc/ChangeLog

+2013-06-05  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	* config/arm/arm.c (MAX_INSN_PER_IT_BLOCK): New macro.
+	(arm_option_override): Override arm_restrict_it where appropriate.
+	(thumb2_final_prescan_insn): Use MAX_INSN_PER_IT_BLOCK.
+	* config/arm/arm.opt (mrestrict-it): New command-line option.
+	* doc/invoke.texi: Document -mrestrict-it.
+
 2013-06-05  David Malcolm  <dmalcolm@redhat.com>
 
 	* tsan.c (tsan_atomic_table): Make const.

gcc/config/arm/arm.c

@@ -662,6 +662,10 @@ static const struct attribute_spec arm_attribute_table[] =
 #undef TARGET_ASAN_SHADOW_OFFSET
 #define TARGET_ASAN_SHADOW_OFFSET arm_asan_shadow_offset
 
+#undef MAX_INSN_PER_IT_BLOCK
+#define MAX_INSN_PER_IT_BLOCK (arm_restrict_it ? 1 : 4)
+
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 /* Obstack for minipool constant handling.  */
@@ -1871,6 +1875,11 @@ arm_option_override (void)
   arm_arch_thumb_hwdiv = (insn_flags & FL_THUMB_DIV) != 0;
   arm_arch_arm_hwdiv = (insn_flags & FL_ARM_DIV) != 0;
   arm_tune_cortex_a9 = (arm_tune == cortexa9) != 0;
+  if (arm_restrict_it == 2)
+    arm_restrict_it = arm_arch8 && TARGET_THUMB2;
+
+  if (!TARGET_THUMB2)
+    arm_restrict_it = 0;
 
   /* If we are not using the default (ARM mode) section anchor offset
      ranges, then set the correct ranges now.  */
@@ -19593,7 +19602,7 @@ thumb2_final_prescan_insn (rtx insn)
 	break;
       /* Allow up to 4 conditionally executed instructions in a block.  */
       n = get_attr_ce_count (insn);
-      if (arm_condexec_masklen + n > 4)
+      if (arm_condexec_masklen + n > MAX_INSN_PER_IT_BLOCK)
 	break;
 
       predicate = COND_EXEC_TEST (body);

gcc/config/arm/arm.opt

@@ -239,6 +239,10 @@ mword-relocations
 Target Report Var(target_word_relocations) Init(TARGET_DEFAULT_WORD_RELOCATIONS)
 Only generate absolute relocations on word sized values.
 
+mrestrict-it
+Target Report Var(arm_restrict_it) Init(2)
+Generate IT blocks appropriate for ARMv8.
+
 mfix-cortex-m3-ldrd
 Target Report Var(fix_cm3_ldrd) Init(2)
 Avoid overlapping destination and address registers on LDRD instructions

gcc/doc/invoke.texi

@@ -512,7 +512,8 @@ Objective-C and Objective-C++ Dialects}.
 -mword-relocations @gol
 -mfix-cortex-m3-ldrd @gol
 -munaligned-access @gol
--mneon-for-64bits}
+-mneon-for-64bits @gol
+-mrestrict-it}
 
 @emph{AVR Options}
 @gccoptlist{-mmcu=@var{mcu} -maccumulate-args -mbranch-cost=@var{cost} @gol
@@ -11633,6 +11634,12 @@ defined.
 Enables using Neon to handle scalar 64-bits operations. This is
 disabled by default since the cost of moving data from core registers
 to Neon is high.
+
+@item -mrestrict-it
+@opindex mrestrict-it
+Restricts generation of IT blocks to conform to the rules of ARMv8.
+IT blocks can only contain a single 16-bit instruction from a select
+set of instructions. This option is on by default for ARMv8 Thumb mode.
 @end table
 
 @node AVR Options