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[PATCH][GCC][mid-end] Fix DSE big-endian subreg crash
- From: Tamar Christina <tamar dot christina at arm dot com>
- To: gcc-patches at gcc dot gnu dot org
- Cc: nd at arm dot com, law at redhat dot com, rguenther at suse dot de, ian at airs dot com
- Date: Wed, 15 Aug 2018 13:57:11 +0100
- Subject: [PATCH][GCC][mid-end] Fix DSE big-endian subreg crash
Hi All,
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.
I don't have a target independent test for this because it depends
on the target having a 48byte mode and using it for loads.
Cross compiled and regtested on
aarch64_be-none-elf
and no issues
Boostrapped and regtested
aarch64-none-linux-gnu
and found no issues.
Bootstrapped on
x86_64-pc-linux-gnu
arm-none-linux-gnueabihf
and no issues.
Ok for trunk?
Thanks,
Tamar
gcc/ChangeLog:
2018-08-15 Tamar Christina <tamar.christina@arm.com>
* expmed.c (extract_low_bits): Reject invalid subregs early.
gcc/testsuite/ChangeLog:
2018-08-15 Tamar Christina <tamar.christina@arm.com>
* gcc.target/aarch64/large_struct_copy.c: New test.
--
diff --git a/gcc/expmed.c b/gcc/expmed.c
index 101e7b88107702b06276cfcd94319d6b79751368..8a1222fa69e88fa7ee6e2c3210d6747d6536de98 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -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;
diff --git a/gcc/testsuite/gcc.target/aarch64/large_struct_copy.c b/gcc/testsuite/gcc.target/aarch64/large_struct_copy.c
new file mode 100644
index 0000000000000000000000000000000000000000..2b5e7801bad0598138cbcee7b2f4ffffaaf438df
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/large_struct_copy.c
@@ -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;
+}
+