middle-end: updating the reg use in exit block for -fzero-call-used-regs [PR100775]

In the pass_zero_call_used_regs, when updating dataflow info after adding
the register zeroing sequence in the epilogue of the function, we should
call "df_update_exit_block_uses" to update the register use information in
the exit block to include all the registers that have been zeroed.

2022-02-10  Qing Zhao  <qing.zhao@oracle.com>

gcc/ChangeLog:

	PR middle-end/100775
	* function.cc (gen_call_used_regs_seq): Call
	df_update_exit_block_uses when updating df.

gcc/testsuite/ChangeLog:

	PR middle-end/100775
	* gcc.target/arm/pr100775.c: New test.

1 files changed, 9 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.target/arm/pr100775.c b/gcc/testsuite/gcc.target/arm/pr100775.c
new file mode 100644
index 00000000000..c648cd5e8f7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pr100775.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-skip-if "" { ! { arm_thumb1_ok || arm_thumb2_ok } } } */
+/* { dg-options "-mthumb -fzero-call-used-regs=used" } */
+
+int
+foo (int x)
+{
+  return x;
+}