Re: [PATCH] avr: Set param_min_pagesize to 0 [PR105523]

[<SenthilKumar.Selvaraj@microchip.com>]

On 26/04/23, 5:51 PM, "Richard Biener" <richard.guenther@gmail.com <mailto:richard.guenther@gmail.com>> wrote:
> On Wed, Apr 26, 2023 at 12:56 PM <SenthilKumar.Selvaraj@microchip.com <mailto:SenthilKumar.Selvaraj@microchip.com>> wrote:
> >
> > On Wed, Apr 26, 2023 at 3:15 PM Richard Biener via Gcc-patches <gcc-patches@gcc.gnu.org <mailto:gcc-patches@gcc.gnu.org>> wrote:
> > >
> > > On Wed, Apr 26, 2023 at 11:42 AM Richard Biener
> > > <richard.guenther@gmail.com <mailto:richard.guenther@gmail.com>> wrote:
> > > >
> > > > On Wed, Apr 26, 2023 at 11:01 AM SenthilKumar.Selvaraj--- via
> > > > Gcc-patches <gcc-patches@gcc.gnu.org <mailto:gcc-patches@gcc.gnu.org>> wrote:
> > > > >
> > > > > Hi,
> > > > >
> > > > > This patch fixes PR 105523 by setting param_min_pagesize to 0 for the
> > > > > avr target. For this target, zero and offsets from zero are perfectly
> > > > > valid addresses, and the default value of param_min_pagesize ends up
> > > > > triggering warnings on valid memory accesses.
> > > >
> > > > I think the proper configuration is to have
> > > > DEFAULT_ADDR_SPACE_ZERO_ADDRESS_VALID
> > >
> > > Err, TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID
> >
> > That worked. Ok for trunk and backporting to 13 and 12 branches
> > (pending regression testing)?
> 
> 
> OK, but please let Denis time to comment.

Didn't hear from Denis. When running regression tests with this patch,
I found that some tests with -fdelete-null-pointer-checks were
failing. Commit 19416210b37db0584cd0b3f3b3961324b8973d25 made
-fdelete-null-pointer-checks false by default, while still allowing it
to be overridden from the command line (it was previously
unconditionally false).

To keep the same behavior, I modified the hook to report zero
addresses as valid only if -fdelete-null-pointer-checks is not set.
With this change, all regression tests pass.

Ok for trunk and backporting to 13 and 12 branches?

Regards
Senthil

	PR 105523

gcc/ChangeLog:

	* config/avr/avr.cc (avr_addr_space_zero_address_valid):
	(TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID): Return true if
    flag_delete_null_pointer_checks is not set.

gcc/testsuite/ChangeLog:

	* gcc.target/avr/pr105523.c: New test.


diff --git gcc/config/avr/avr.cc gcc/config/avr/avr.cc
index d5af40f..4c9eb84 100644
--- gcc/config/avr/avr.cc
+++ gcc/config/avr/avr.cc
@@ -9787,6 +9787,18 @@ avr_addr_space_diagnose_usage (addr_space_t as, location_t loc)
   (void) avr_addr_space_supported_p (as, loc);
 }
 
+/* Implement `TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID. Zero is a valid
+   address in all address spaces. Even in ADDR_SPACE_FLASH1 etc..,
+   a zero address is valid and means 0x<RAMPZ val>0000, where RAMPZ is
+   set to the appropriate segment value.
+   If the user explicitly passes in -fdelete-null-pointer-checks though,
+   assume zero addresses are invalid.*/
+
+static bool
+avr_addr_space_zero_address_valid (addr_space_t as ATTRIBUTE_UNUSED)
+{
+  return flag_delete_null_pointer_checks == 0;
+}
 
 /* Look if DECL shall be placed in program memory space by
    means of attribute `progmem' or some address-space qualifier.
@@ -14687,6 +14699,9 @@ avr_float_lib_compare_returns_bool (machine_mode mode, enum rtx_code)
 #undef  TARGET_ADDR_SPACE_DIAGNOSE_USAGE
 #define TARGET_ADDR_SPACE_DIAGNOSE_USAGE avr_addr_space_diagnose_usage
 
+#undef  TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID
+#define TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID avr_addr_space_zero_address_valid
+
 #undef  TARGET_MODE_DEPENDENT_ADDRESS_P
 #define TARGET_MODE_DEPENDENT_ADDRESS_P avr_mode_dependent_address_p
 
diff --git gcc/testsuite/gcc.target/avr/pr105523.c gcc/testsuite/gcc.target/avr/pr105523.c
new file mode 100644
index 0000000..fbbf7bf
--- /dev/null
+++ gcc/testsuite/gcc.target/avr/pr105523.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-Os -Wall" } */
+
+/* Verify no "array subscript 0 is outside array bounds of" is generated
+   for accessing memory addresses in the 0-4096 range. */
+
+typedef __UINT8_TYPE__ uint8_t;
+
+#define SREG (*(volatile uint8_t*) (0x3F + __AVR_SFR_OFFSET__ ))
+
+void bar (void)
+{
+    SREG = 0;
+}