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arm: fix UB due to missing mode check [PR100311]

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Some places in the compiler iterate over all the fixed registers to
check if that register can be used in a particular mode.  The idiom is
to iterate over the register and then for that register, if it
supports the current mode to check all that register and any
additional registers needed (HARD_REGNO_NREGS).  If these two checks
are not fully aligned then it is possible to generate a buffer overrun
when testing data objects that are sized by the number of hard regs in
the machine.

The VPR register is a case where these checks were not consistent and
because this is the last HARD register the result was that we ended up
overflowing the fixed_regs array.

gcc:
	PR target/100311
	* config/arm/arm.c (arm_hard_regno_mode_ok): Only allow VPR to be
	used in HImode.
This commit is contained in:
Richard Earnshaw 2021-04-28 17:56:38 +01:00
parent e1543e694d
commit 59f5d16f2c
1 changed files with 1 additions and 1 deletions
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2
gcc/config/arm/arm.c
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@ -25269,7 +25269,7 @@ arm_hard_regno_mode_ok (unsigned int regno, machine_mode mode)
return false;
if (IS_VPR_REGNUM (regno))
return true;
return mode == HImode;
if (TARGET_THUMB1)
/* For the Thumb we only allow values bigger than SImode in