[PATCH][ARM] Fix shrink-wrap regressions on arm thumb2 test

[Jiong Wang <jiong dot wang at arm dot com>]

the patch athttps://gcc.gnu.org/ml/gcc-patches/2014-07/msg00961.html

actually has one glitch on if check.

thumb target is code size sensitive, the best solution is we set "prefer_callee_reg_p" to
true if we know that shrink-wrap will be performanced if prefer_callee_reg_p is true.

but unfortunately, shrink-wrap judegement is done after these code, so we should always
prefer "r3" instead of "prefer_callee_reg_p" on thumb.

previously, the logic is wrong, everything pass check on A, will pass check on B.

  && (TARGET_THUMB2
      || !(TARGET_LDRD && current_tune->prefer_ldrd_strd)))  <=A
    {
      reg = 3;
      if (!(TARGET_LDRD && current_tune->prefer_ldrd_strd)) <= B
        prefer_callee_reg_p = true;
    }


the condition check
 
 if (!(TARGET_LDRD && current_tune->prefer_ldrd_strd))

should be

  if (!TARGET_THUMB2)

it's not exposed before because my local toolchain is not configured with extra cflags that
the default dejagnu env is still for old cpu like arm7, that testcases which requrie_thumb2
are marked as UNSUPPORTTED. sorry for makeing trouble.

after this fix, the code behave as expected, we only play the "prefer_callee_reg_p" trick
on arm32 target.


testcase regressions fixed
===
-FAIL: gcc.target/arm/pr43920-2.c object-size text <= 54
-FAIL: gcc.target/arm/pr45701-1.c scan-assembler push\t{r3
-FAIL: gcc.target/arm/pr45701-1.c scan-assembler-not r8
-FAIL: gcc.target/arm/pr45701-2.c scan-assembler push\t{r3
-FAIL: gcc.target/arm/pr45701-2.c scan-assembler-not r8
+PASS: gcc.target/arm/pr43920-2.c object-size text <= 54
+PASS: gcc.target/arm/pr45701-1.c scan-assembler push\t{r3
+PASS: gcc.target/arm/pr45701-1.c scan-assembler-not r8
+PASS: gcc.target/arm/pr45701-2.c scan-assembler push\t{r3
+PASS: gcc.target/arm/pr45701-2.c scan-assembler-not r8

and all those ira-shrink* testcases not affected, still all pass.

test done
===
* pass bootstrap on chromebook with both arm and thumb mode
* no regression on arm-none-eabi (configured with armv8-a) full toolchain test.

ok to install?

thanks,
Jiong

gcc/
  * config/arm/arm.c (arm_get_frame_offsets): !(TARGET_LDRD && current_tune->prefer_ldrd_strd)
  should be "!TARGET_THUMB2".

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 7e62ba5..4c8b2c2 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -20803,7 +20803,7 @@ arm_get_frame_offsets (void)
 		  || !(TARGET_LDRD && current_tune->prefer_ldrd_strd)))
 	    {
 	      reg = 3;
-	      if (!(TARGET_LDRD && current_tune->prefer_ldrd_strd))
+	      if (!TARGET_THUMB2)
 		prefer_callee_reg_p = true;
 	    }
 	  if (reg == -1