This patch lets
const __flashx *x = NULL;
compile to x = 0x000000 instead of the previous x = 0x800000.
Apart from that, -Waddr-space-convert warns no more for such
code, which removes some itches when using a null pointer.
Dito for __flash.
Applied as obvious.
Johann
--
AVR: target/121277 - Don't load 0x800000 with const __flashx *x = NULL.
Converting from generic AS to __flashx used the same rule like
for __memx, which tags RAM (generic AS) locations by setting bit 23.
The justification was that generic isn't a subset of __flashx, though
that lead to surprises with code like const __flashx *x = NULL.
The natural thing to do is to just load 0x000000 in that case,
so that the null pointer works in __flashx as expected.
Apart from that, converting NULL to __flashx (or __flash) no more
raises a -Waddr-space-convert diagnostic.
gcc/
PR target/121277
* config/avr/avr.cc (avr_addr_space_convert): When converting
from generic AS to __flashx, don't set bit 23.
(avr_convert_to_type): Don't -Waddr-space-convert when NULL
is converted to __flashx or to __flash. AVR: target/121277 - Don't load 0x800000 with const __flashx *x = NULL.
Converting from generic AS to __flashx used the same rule like
for __memx, which tags RAM (generic AS) locations by setting bit 23.
The justification was that generic isn't a subset of __flashx, though
that lead to surprises with code like const __flashx *x = NULL.
The natural thing to do is to just load 0x000000 in that case,
so that the null pointer works in __flashx as expected.
Apart from that, converting NULL to __flashx (or __flash) no more
raises a -Waddr-space-convert diagnostic.
gcc/
PR target/121277
* config/avr/avr.cc (avr_addr_space_convert): When converting
from generic AS to __flashx, don't set bit 23.
(avr_convert_to_type): Don't -Waddr-space-convert when NULL
is converted to __flashx or to __flash.
diff --git a/gcc/config/avr/avr.cc b/gcc/config/avr/avr.cc
index c469297d6d0..94684468de3 100644
--- a/gcc/config/avr/avr.cc
+++ b/gcc/config/avr/avr.cc
@@ -14984,10 +14984,11 @@ avr_addr_space_convert (rtx src, tree type_old, tree type_new)
/* Linearize memory: RAM has bit 23 set. When as_new = __flashx then
this is basically UB since __flashx mistreats RAM addresses, but there
- is no way to bail out. (Though -Waddr-space-convert will tell.) */
+ is no way to bail out. (Though -Waddr-space-convert will tell.)
+ ...but PR121277 is confusing, in particular when NULL is coming in. */
int msb = ADDR_SPACE_GENERIC_P (as_old)
- ? 0x80
+ ? as_new == ADDR_SPACE_MEMX ? 0x80 : 0x00
: avr_addrspace[as_old].segment;
src = force_reg (Pmode, src);
@@ -15085,10 +15086,16 @@ avr_convert_to_type (tree type, tree expr)
const char *name_old = avr_addrspace[as_old].name;
const char *name_new = avr_addrspace[as_new].name;
- warning (OPT_Waddr_space_convert,
- "conversion from address space %qs to address space %qs",
- ADDR_SPACE_GENERIC_P (as_old) ? "generic" : name_old,
- ADDR_SPACE_GENERIC_P (as_new) ? "generic" : name_new);
+ // Be relaxed when NULL is used, and when 0x0 stands for
+ // address 0x0.
+ bool nowarn = (expr == null_pointer_node
+ && (as_new == ADDR_SPACE_FLASHX
+ || as_new == ADDR_SPACE_FLASH));
+ if (!nowarn)
+ warning (OPT_Waddr_space_convert,
+ "conversion from address space %qs to address space %qs",
+ ADDR_SPACE_GENERIC_P (as_old) ? "generic" : name_old,
+ ADDR_SPACE_GENERIC_P (as_new) ? "generic" : name_new);
return fold_build1_loc (loc, ADDR_SPACE_CONVERT_EXPR, type, expr);
}
