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Fix DSE big-endian subreg crash on AArch64.

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This patch fixes an ICE that would happen when extract_low_bits
is called with modes for which you can't extract a valid subreg.
e.g. taking a 32 bytes subreg from a 48 byte mode.

The ICE happens because convert_modes which eventually calls
simplify_gen_subreg does not expect the convertion to fail.

The assert in gen_lowpart_general would then be hit.  The patch
changes it to validate the subreg before trying to convert the
modes.  If the subreg is not possible we return NULL_RTX and bail
out early.

gcc/ChangeLog:

2018-08-21  Tamar Christina  <tamar.christina@arm.com>

	* expmed.c (extract_low_bits): Reject invalid subregs early.

gcc/testsuite/ChangeLog:

2018-08-21  Tamar Christina  <tamar.christina@arm.com>

	* gcc.target/aarch64/large_struct_copy.c: New test.

From-SVN: r263696
This commit is contained in:
Tamar Christina 2018-08-21 09:55:07 +00:00 • committed by Tamar Christina
parent 25d4036370
commit daa9715842
4 changed files with 35 additions and 0 deletions
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4
gcc/ChangeLog
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@ -1,3 +1,7 @@
2018-08-21 Tamar Christina <tamar.christina@arm.com>
* expmed.c (extract_low_bits): Reject invalid subregs early.
2018-08-21 Bernd Edlinger <bernd.edlinger@hotmail.de>
PR middle-end/86121

4
gcc/expmed.c
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@ -2392,6 +2392,10 @@ extract_low_bits (machine_mode mode, machine_mode src_mode, rtx src)
return NULL_RTX;
src = gen_lowpart (src_int_mode, src);
if (!validate_subreg (int_mode, src_int_mode, src,
subreg_lowpart_offset (int_mode, src_int_mode)))
return NULL_RTX;
src = convert_modes (int_mode, src_int_mode, src, true);
src = gen_lowpart (mode, src);
return src;

4
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,7 @@
2018-08-21 Tamar Christina <tamar.christina@arm.com>
* gcc.target/aarch64/large_struct_copy.c: New test.
2018-08-21 Szabolcs Nagy <szabolcs.nagy@arm.com>
* g++.dg/torture/pr86763.C: Restrict to *-*-linux*.

23
gcc/testsuite/gcc.target/aarch64/large_struct_copy.c Normal file
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@ -0,0 +1,23 @@
/* { dg-do compile } */
/* { dg-options "-O2" } */
typedef unsigned __attribute__((mode(DI))) uint64_t;
struct S0 {
uint64_t f1;
uint64_t f2;
uint64_t f3;
uint64_t f4;
uint64_t f5;
} a;
struct S2 {
uint64_t f0;
uint64_t f2;
struct S0 f3;
};
void fn1 () {
struct S2 b = {0, 1, 7, 4073709551611, 4, 8, 7};
a = b.f3;
}