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arm: PR target/95646: Do not clobber callee saved registers with CMSE

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As reported in bugzilla when the -mcmse option is used while compiling for size
(-Os) with a thumb-1 target the generated code will clear the registers r7-r10.
These however are callee saved and should be preserved accross ABI boundaries.
The reason this happens is because these registers are made "fixed" when
optimising for size with Thumb-1 in a way to make sure they are not used, as
pushing and popping hi-registers requires extra moves to and from LO_REGS.

To fix this, this patch uses 'callee_saved_reg_p', which accounts for this
optimisation, instead of 'call_used_or_fixed_reg_p'. Be aware of
'callee_saved_reg_p''s definition, as it does still take call used registers
into account, which aren't callee_saved in my opinion, so it is a rather
misnoemer, works in our advantage here though as it does exactly what we need.

Regression tested on arm-none-eabi.

Is this OK for trunk? (Will eventually backport to previous versions if stable.)

gcc/ChangeLog:
2020-06-19  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	PR target/95646
	* config/arm/arm.c: (cmse_nonsecure_entry_clear_before_return): Use
	'callee_saved_reg_p' instead of 'calL_used_or_fixed_reg_p'.

gcc/testsuite/ChangeLog:
2020-06-19  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	PR target/95646
	* gcc.target/arm/pr95646.c: New test.
This commit is contained in:
Andre Simoes Dias Vieira 2020-06-23 15:20:17 +01:00 committed by Andre Vieira
parent b81d4f1e3d
commit 5f426554fd
2 changed files with 33 additions and 1 deletions
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2
gcc/config/arm/arm.c
View File

@ -26960,7 +26960,7 @@ cmse_nonsecure_entry_clear_before_return (void)
continue;
if (IN_RANGE (regno, IP_REGNUM, PC_REGNUM))
continue;
if (call_used_or_fixed_reg_p (regno)
if (!callee_saved_reg_p (regno)
&& (!IN_RANGE (regno, FIRST_VFP_REGNUM, LAST_VFP_REGNUM)
|| TARGET_HARD_FLOAT))
bitmap_set_bit (to_clear_bitmap, regno);

32
gcc/testsuite/gcc.target/arm/pr95646.c Normal file
View File

@ -0,0 +1,32 @@
/* { dg-do compile } */
/* { dg-skip-if "avoid conflicting multilib options" { *-*-* } { "-march=*" } { "-march=armv8-m.base" } } */
/* { dg-skip-if "avoid conflicting multilib options" { *-*-* } { "-mcpu=*" } { "-mcpu=cortex-m23" } } */
/* { dg-skip-if "avoid conflicting multilib options" { *-*-* } { "-mfpu=*" } { } } */
/* { dg-skip-if "avoid conflicting multilib options" { *-*-* } { "-mfloat-abi=*" } { "-mfloat-abi=soft" } } */
/* { dg-options "-mcpu=cortex-m23 -mcmse" } */
/* { dg-additional-options "-Os" } */
/* { dg-final { check-function-bodies "**" "" } } */
int __attribute__ ((cmse_nonsecure_entry))
foo (void)
{
return 1;
}
/* { { dg-final { scan-assembler-not "mov\tr9, r0" } } */
/*
** __acle_se_bar:
** mov (r[0-3]), r9
** push {\1}
** ...
** pop {(r[0-3])}
** mov r9, \2
** ...
** bxns lr
*/
int __attribute__ ((cmse_nonsecure_entry))
bar (void)
{
asm ("": : : "r9");
return 1;
}