To date, each named address space is implemented as a subset
of all the other address spaces, which allows code like
char read_char (const char *addr, bool in_flash)
{
return in_flash
? *(const __flash char*) addr // Read from program memory.
: *addr; // Read from RAM.
}
even though __flash is not a subset of Generic.
This patch introduces new target option -mstrict-addr-space-subsets
which instructs avr_addr_space_subset_p to implement the address
space subset relations like they actually are, i.e.
__memx > __flashx > __flash, __flash1, ..., __flash5
__memx > Generic
Ok for trunk?
Johann
--
gcc/
* config/avr/avr.opt (-mstrict-addr-space-subsets): New
target option.
* config/avr/avr.cc (avr_addr_space_subset_p): Use it.
* doc/invoke.texi (AVR Options): Document it.diff --git a/gcc/config/avr/avr.cc b/gcc/config/avr/avr.cc
index 87c4044f076..7c003941bdc 100644
--- a/gcc/config/avr/avr.cc
+++ b/gcc/config/avr/avr.cc
@@ -15404,18 +15404,7 @@ avr_addr_space_convert (rtx src, tree type_old, tree type_new)
}
-/* Implement `TARGET_ADDR_SPACE_SUBSET_P'. */
-
-static bool
-avr_addr_space_subset_p (addr_space_t /*subset*/, addr_space_t /*superset*/)
-{
- /* Allow any kind of pointer mess. */
-
- return true;
-}
-
-
-/* Helps the next function. */
+/* Helps the next two functions. */
static bool
avr_addr_space_contains (addr_space_t super, addr_space_t sub)
@@ -15427,6 +15416,17 @@ avr_addr_space_contains (addr_space_t super, addr_space_t sub)
}
+/* Implement `TARGET_ADDR_SPACE_SUBSET_P'. */
+
+static bool
+avr_addr_space_subset_p (addr_space_t subset, addr_space_t superset)
+{
+ // Allow any kind of pointer casts with -mno-strict-addr-space-subsets.
+ return (!avropt_strict_addr_space_subsets
+ || avr_addr_space_contains (superset, subset));
+}
+
+
/* Implement `TARGET_CONVERT_TO_TYPE'. */
static tree
diff --git a/gcc/config/avr/avr.opt b/gcc/config/avr/avr.opt
index 97d207726ba..d56061b50b6 100644
--- a/gcc/config/avr/avr.opt
+++ b/gcc/config/avr/avr.opt
@@ -115,6 +115,10 @@ msplit-ldst
Target Var(avropt_split_ldst) Init(0) Optimization
Optimization. Split most of the load and store instructions into byte load and stores.
+mstrict-addr-space-subsets
+Target Var(avropt_strict_addr_space_subsets) Init(0)
+Implement strict named address space subset relations.
+
mstrict-X
Target Var(avropt_strict_X) Init(0) Optimization
Optimization. When accessing RAM, use X as imposed by the hardware, i.e. just use pre-decrement, post-increment and indirect addressing with the X register. Without this option, the compiler may assume that there is an addressing mode X+const similar to Y+const and Z+const and emit instructions to emulate such an addressing mode for X.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 2e53a8c8a7e..d6cfc459853 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -991,7 +991,7 @@ Objective-C and Objective-C++ Dialects}.
-mdouble=@var{bits} -mlong-double=@var{bits} -mno-call-main
-mn_flash=@var{size} -mfract-convert-truncate -mno-interrupts
-mmain-is-OS_task -mrelax -mpmem-wrap-around
--mrmw -mstrict-X -mtiny-stack
+-mrmw -mstrict-addr-space-subsets -mstrict-X -mtiny-stack
-mrodata-in-ram -msplit-bit-shift -msplit-ldst -mshort-calls
-mskip-bug -muse-nonzero-bits -nodevicelib -nodevicespecs
-Wasm-len-notes -Waddr-space-convert -Wmisspelled-isr}
@@ -24595,6 +24595,23 @@ aspect of the optimization.
@item -mfuse-move2
Run a post combine optimization pass that tries to fuse move instructions.
+@opindex mstrict-addr-space-subsets
+@item -mstrict-addr-space-subsets
+Impose strict named address space subset relations. Without this option,
+every address space is considered to be a subset of all the other spaces,
+which allows to write code like
+@example
+char read_char (const char *addr, bool in_flash)
+@{
+ return in_flash
+ ? *(const __flash char*) addr // Read from program memory.
+ : *addr; // Read from RAM.
+@}
+@end example
+When the option is on, such code is rejected since address space
+@code{__flash} is not a subset of the generic space, and hence the
+cast in the above code is prohibited.
+
@opindex mstrict-X
@item -mstrict-X
Use address register @code{X} in a way proposed by the hardware. This means
