Hi,
PR 100775 ( ICE: in df_exit_block_bitmap_verify, at df-scan.c:4164 with -mthumb
-fzero-call-used-regs=used)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100775
Although the ICE only happens on arm, but this is a bug in the middle end. So,
I think this bug has higher priority,
Need to be included into gcc12, and also need to be back ported to gcc11.
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.
The change has been bootstrapped and reg-tested on both x86 and aarch64 (with
-enable-checking=yes,rtl,df).
Since I cannot find an arm machine, no bootstrap and reg-tested on arm yet.
For the arm failure, I just tested it with the cross build and it has no issue
withe the fix.
(One question here:
Previously, I though “df_set_bb_dirty (EXIT_BLOCK_PTR_FOR_FN (cfun))” and a
later “df_analyze()” should rescan
the changed exit block of the function, and update all the df info
automatically, it apparently not the case, the register
use info at exit block is not automatically updated, we have to add an
explicitly call to “df_update_exit_block_uses”.
I checked the pass_thread_prologue_and_epilogue, looks like it also explicitly
calls “df_update_entry_exit_and_calls”
to update the register use info.
Shall the “df_set_bb_dirty” + “df_analyze” automatically update the reg use
info of the dirty block?).
Let me know whether there is any issue with the fix?
Thanks
Qing
===================================
From e1cca5659c85e7c536f5016a2c75c615e65dba75 Mon Sep 17 00:00:00 2001
From: Qing Zhao <qing.z...@oracle.com>
Date: Fri, 28 Jan 2022 16:29:51 +0000
Subject: [PATCH] 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.
2022-01-27 Qing Zhao <qing.z...@oracle.com>
gcc/ChangeLog:
* function.cc (gen_call_used_regs_seq): Call
df_update_exit_block_uses when updating df.
gcc/testsuite/ChangeLog:
* gcc.target/arm/pr100775.c: New test.
---
gcc/function.cc | 1 +
gcc/testsuite/gcc.target/arm/pr100775.c | 8 ++++++++
2 files changed, 9 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/arm/pr100775.c
diff --git a/gcc/function.cc b/gcc/function.cc
index e1d2565f8d92..c8a77c9a6246 100644
--- a/gcc/function.cc
+++ b/gcc/function.cc
@@ -5942,6 +5942,7 @@ 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 000000000000..dd2255a95492
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pr100775.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-mthumb -fzero-call-used-regs=used" } */
+
+int
+foo (int x)
+{
+ return x;
+}
--
2.27.0
