Hi Sudi,
On 21/03/18 17:44, Sudakshina Das wrote:
Hi
The ICE in the bug report was happening because the macro
USE_RETURN_INSN (FALSE) was returning different values at different
points in the compilation. This was internally occurring because the
function arm_compute_static_chain_stack_bytes () which was dependent on
arm_r3_live_at_start_p () was giving a different value after the
cond_exec instructions were created in ce3 causing the liveness of r3
to escape up to the start block.
The function arm_compute_static_chain_stack_bytes () should really
only compute the value once during epilogue/prologue stage. This pass
introduces a new member 'static_chain_stack_bytes' to the target
definition of the struct machine_function which gets calculated in
expand_prologue and is the value that is returned by
arm_compute_static_chain_stack_bytes () beyond that.
Testing done: Bootstrapped and regtested on arm-none-linux-gnueabihf
and added the reported test to the testsuite.
Is this ok for trunk?
Thanks for working on this.
I agree with the approach, I have a couple of comments inline.
Sudi
ChangeLog entries:
*** gcc/ChangeLog ***
2018-03-21 Sudakshina Das <sudi.das@arm.com>
PR target/84826
* config/arm/arm.h (machine_function): Add
static_chain_stack_bytes.
* config/arm/arm.c (arm_compute_static_chain_stack_bytes):
Avoid re-computing once computed.
(arm_expand_prologue): Compute machine->static_chain_stack_bytes.
(arm_init_machine_status): Initialize
machine->static_chain_stack_bytes.
*** gcc/testsuite/ChangeLog ***
2018-03-21 Sudakshina Das <sudi.das@arm.com>
PR target/84826
* gcc.target/arm/pr84826.c: New test
diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index bbf3937..2809112 100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -1384,6 +1384,9 @@ typedef struct GTY(()) machine_function
machine_mode thumb1_cc_mode;
/* Set to 1 after arm_reorg has started. */
int after_arm_reorg;
+ /* The number of bytes used to store the static chain register on the
+ stack, above the stack frame. */
+ int static_chain_stack_bytes;
}
machine_function;
#endif
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index cb6ab81..bc31810 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -19392,6 +19392,11 @@ arm_r3_live_at_start_p (void)
static int
arm_compute_static_chain_stack_bytes (void)
{
+ /* Once the value is updated from the init value of -1, do not
+ re-compute. */
+ if (cfun->machine->static_chain_stack_bytes != -1)
+ return cfun->machine->static_chain_stack_bytes;
+
My concern is that this approach caches the first value that is computed for static_chain_stack_bytes.
I believe the layout frame code is called multiple times during register allocation as it goes through
the motions and I think we want the last value it computes during reload
How about we do something like:
if (cfun->machine->static_chain_stack_bytes != -1 &&epilogue_completed)
return cfun->machine->static_chain_stack_bytes;
?...
/* See the defining assertion in arm_expand_prologue. */
if (IS_NESTED (arm_current_func_type ())
&& ((TARGET_APCS_FRAME && frame_pointer_needed && TARGET_ARM)
@@ -21699,6 +21704,11 @@ arm_expand_prologue (void)
emit_insn (gen_movsi (stack_pointer_rtx, r1));
}
+ /* Let's compute the static_chain_stack_bytes required and store it. Right
+ now the value must the -1 as stored by arm_init_machine_status (). */
... this comment would need to be tweaked as cfun->machine->static_chain_stack_bytes may hold
an intermediate value computed in reload or some other point before epilogue_completed.
+ cfun->machine->static_chain_stack_bytes
+ = arm_compute_static_chain_stack_bytes ();
+