[gcc r11-9663] middle-end/100775 - updating the reg use in exit block for -fzero-call-used-regs

[Qing Zhao <qinzhao@gcc.gnu.org>]

https://gcc.gnu.org/g:9b1faeb5bfef258780e313aa8302a43f98f3b442

commit r11-9663-g9b1faeb5bfef258780e313aa8302a43f98f3b442
Author: Qing Zhao <qing.zhao@oracle.com>
Date:   Wed Mar 16 20:18:54 2022 +0000

    middle-end/100775 - updating the reg use in exit block for -fzero-call-used-regs
    
    GCC11 backport.
    
    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.
    
    gcc/ChangeLog:
    
            PR middle-end/100775
            * function.c (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.

Diff:
---
 gcc/function.c                          | 2 +-
 gcc/testsuite/gcc.target/arm/pr100775.c | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/gcc/function.c b/gcc/function.c
index fc7b147b5f1..0495e9f1b81 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -5922,7 +5922,7 @@ gen_call_used_regs_seq (rtx_insn *ret, unsigned int zero_regs_type)
 
       /* Update the data flow information.  */
       crtl->must_be_zero_on_return |= zeroed_hardregs;
-      df_set_bb_dirty (EXIT_BLOCK_PTR_FOR_FN (cfun));
+      df_update_exit_block_uses ();
     }
 }
 
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;
+}