The issue here is the code we emit for mode-switching can change when -g
is added to the command line. This is caused by processing debug notes
occurring after a call which is the last real statement in a basic block.
Without -g the CALL_INSN is literally the last insn in the block and the
loop exits. If mode switching after the call is needed, it'll be
handled as we process outgoing edges.
With -g the loop iterates again and in the processing of the node the
backend signals that a mode switch is necessary.
I pondered fixing this in the target, but the better fix is to ignore
the debug notes in the insn stream.
I did a cursory review of some of the other compare-debug failures, but
did not immediately see others which would likely be fixed by this
change. Sigh.
Anyway, bootstrapped and regression tested on x86. Regression tested on
rv64 as well.
Pushing to the trunk.
Jeff
commit 50531b6d400945793a1d549e6ee941d989319d42
Author: jlaw <jeffreya...@gmail.com>
Date: Sat Mar 9 19:27:32 2024 -0700
[committed] [PR target/111362] Fix compare-debug issue with mode switching
The issue here is the code we emit for mode-switching can change when -g is
added to the command line. This is caused by processing debug notes
occurring
after a call which is the last real statement in a basic block.
Without -g the CALL_INSN is literally the last insn in the block and the
loop
exits. If mode switching after the call is needed, it'll be handled as we
process outgoing edges.
With -g the loop iterates again and in the processing of the node the
backend
signals that a mode switch is necessary.
I pondered fixing this in the target, but the better fix is to ignore the
debug
notes in the insn stream.
I did a cursory review of some of the other compare-debug failures, but did
not
immediately see others which would likely be fixed by this change. Sigh.
Anyway, bootstrapped and regression tested on x86. Regression tested on
rv64
as well.
PR target/111362
gcc/
* mode-switching.cc (optimize_mode_switching): Only process
NONDEBUG insns.
gcc/testsuite
* gcc.target/riscv/compare-debug-1.c: New test.
* gcc.target/riscv/compare-debug-2.c: New test.
diff --git a/gcc/mode-switching.cc b/gcc/mode-switching.cc
index 583929184ce..a145b77397d 100644
--- a/gcc/mode-switching.cc
+++ b/gcc/mode-switching.cc
@@ -959,7 +959,7 @@ optimize_mode_switching (void)
FOR_BB_INSNS (bb, insn)
{
- if (INSN_P (insn))
+ if (NONDEBUG_INSN_P (insn))
{
int mode = targetm.mode_switching.needed (e, insn, live_now);
rtx link;
diff --git a/gcc/testsuite/gcc.target/riscv/compare-debug-1.c
b/gcc/testsuite/gcc.target/riscv/compare-debug-1.c
new file mode 100644
index 00000000000..d65bb287b9a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/compare-debug-1.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fno-tree-ch --param=max-completely-peel-times=0
-march=rv64iv -mabi=lp64d -fcompare-debug" } */
+
+
+void
+foo(void) {
+ for (unsigned i = 0; i < sizeof(foo); i++)
+ __builtin_printf("%d", i);
+}
diff --git a/gcc/testsuite/gcc.target/riscv/compare-debug-2.c
b/gcc/testsuite/gcc.target/riscv/compare-debug-2.c
new file mode 100644
index 00000000000..d87758475e4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/compare-debug-2.c
@@ -0,0 +1,3 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fno-tree-ch --param=max-completely-peel-times=0
-march=rv64iv -mabi=lp64d -fno-dce -fschedule-insns -fcompare-debug" } */
+#include "compare-debug-1.c"
