From d668f875985cf61d3a898d95cf01df90a720e5c2 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Wed, 17 Jul 2024 11:38:33 +0200 Subject: [PATCH] gimple-fold: Fix up __builtin_clear_padding lowering [PR115527] The builtin-clear-padding-6.c testcase fails as clear_padding_type doesn't correctly recompute the buf->size and buf->off members after expanding clearing of an array using a runtime loop. buf->size should be in that case the offset after which it should continue with next members or padding before them modulo UNITS_PER_WORD and buf->off that offset minus buf->size. That is what the code was doing, but with off being the start of the loop cleared array, not its end. So, the last hunk in gimple-fold.cc fixes that. When adding the testcase, I've noticed that the c-c++-common/torture/builtin-clear-padding-* tests, although clearly written as runtime tests to test the builtins at runtime, didn't have { dg-do run } directive and were just compile tests because of that. When adding that to the tests, builtin-clear-padding-1.c was already failing without that clear_padding_type hunk too, but builtin-clear-padding-5.c was still failing even after the change. That is due to a bug in clear_padding_flush which the patch fixes as well - when clear_padding_flush is called with full=true (that happens at the end of the whole __builtin_clear_padding or on those array padding clears done by a runtime loop), it wants to flush all the pending padding clearings rather than just some. If it is at the end of the whole object, it decreases wordsize when needed to make sure the code never writes including RMW cycles to something outside of the object: if ((unsigned HOST_WIDE_INT) (buf->off + i + wordsize) > (unsigned HOST_WIDE_INT) buf->sz) { gcc_assert (wordsize > 1); wordsize /= 2; i -= wordsize; continue; } but if it is full==true flush in the middle, this doesn't happen, but we still process just the buffer bytes before the current end. If that end is not on a wordsize boundary, e.g. on the builtin-clear-padding-5.c test the last chunk is 2 bytes, '\0', '\xff', i is 16 and end is 18, nonzero_last might be equal to the end - i, i.e. 2 here, but still all_ones might be true, so in some spots we just didn't emit any clearing in that last chunk. 2024-07-17 Jakub Jelinek PR middle-end/115527 * gimple-fold.cc (clear_padding_flush): Introduce endsize variable and use it instead of wordsize when comparing it against nonzero_last. (clear_padding_type): Increment off by sz. * c-c++-common/torture/builtin-clear-padding-1.c: Add dg-do run directive. * c-c++-common/torture/builtin-clear-padding-2.c: Likewise. * c-c++-common/torture/builtin-clear-padding-3.c: Likewise. * c-c++-common/torture/builtin-clear-padding-4.c: Likewise. * c-c++-common/torture/builtin-clear-padding-5.c: Likewise. * c-c++-common/torture/builtin-clear-padding-6.c: New test. (cherry picked from commit 8b5919bae11754f4b65a17e63663d3143f9615ac) --- gcc/gimple-fold.cc | 12 ++++---- .../torture/builtin-clear-padding-1.c | 1 + .../torture/builtin-clear-padding-2.c | 1 + .../torture/builtin-clear-padding-3.c | 1 + .../torture/builtin-clear-padding-4.c | 4 +-- .../torture/builtin-clear-padding-5.c | 1 + .../torture/builtin-clear-padding-6.c | 28 +++++++++++++++++++ 7 files changed, 41 insertions(+), 7 deletions(-) create mode 100644 gcc/testsuite/c-c++-common/torture/builtin-clear-padding-6.c diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc index d2a0f6ddf19..3548c914482 100644 --- a/gcc/gimple-fold.cc +++ b/gcc/gimple-fold.cc @@ -4242,7 +4242,8 @@ clear_padding_flush (clear_padding_struct *buf, bool full) i -= wordsize; continue; } - for (size_t j = i; j < i + wordsize && j < end; j++) + size_t endsize = end - i > wordsize ? wordsize : end - i; + for (size_t j = i; j < i + endsize; j++) { if (buf->buf[j]) { @@ -4271,12 +4272,12 @@ clear_padding_flush (clear_padding_struct *buf, bool full) if (padding_bytes) { if (nonzero_first == 0 - && nonzero_last == wordsize + && nonzero_last == endsize && all_ones) { /* All bits are padding and we had some padding before too. Just extend it. */ - padding_bytes += wordsize; + padding_bytes += endsize; continue; } if (all_ones && nonzero_first == 0) @@ -4316,7 +4317,7 @@ clear_padding_flush (clear_padding_struct *buf, bool full) if (nonzero_first == wordsize) /* All bits in a word are 0, there are no padding bits. */ continue; - if (all_ones && nonzero_last == wordsize) + if (all_ones && nonzero_last == endsize) { /* All bits between nonzero_first and end of word are padding bits, start counting padding_bytes. */ @@ -4358,7 +4359,7 @@ clear_padding_flush (clear_padding_struct *buf, bool full) j = k; } } - if (nonzero_last == wordsize) + if (nonzero_last == endsize) padding_bytes = nonzero_last - zero_last; continue; } @@ -4832,6 +4833,7 @@ clear_padding_type (clear_padding_struct *buf, tree type, buf->off = 0; buf->size = 0; clear_padding_emit_loop (buf, elttype, end, for_auto_init); + off += sz; buf->base = base; buf->sz = prev_sz; buf->align = prev_align; diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-1.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-1.c index 6b01a5614b5..f739963cc4d 100644 --- a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-1.c +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-1.c @@ -1,4 +1,5 @@ /* PR libstdc++/88101 */ +/* { dg-do run } */ int i1, i2; long double l1, l2; diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-2.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-2.c index 1188bc07ed2..099f202ebc7 100644 --- a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-2.c +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-2.c @@ -1,4 +1,5 @@ /* PR libstdc++/88101 */ +/* { dg-do run } */ typedef int T __attribute__((aligned (16384))); struct S { char a; short b; long double c; T d; T e; long long f; }; diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-3.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-3.c index edb7c8eb555..27bf8f6dd73 100644 --- a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-3.c +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-3.c @@ -1,4 +1,5 @@ /* PR libstdc++/88101 */ +/* { dg-do run } */ union V { char a; signed char b; unsigned char c; }; struct T { char a; int b; union V c; }; diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-4.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-4.c index 9cb202fc690..ebc58932738 100644 --- a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-4.c +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-4.c @@ -1,6 +1,6 @@ -/* { dg-require-effective-target alloca } */ - /* PR libstdc++/88101 */ +/* { dg-do run } */ +/* { dg-require-effective-target alloca } */ struct S { char a; short b; char c; }; diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-5.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-5.c index d5dbafe1c74..3f7d40fddf8 100644 --- a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-5.c +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-5.c @@ -1,4 +1,5 @@ /* PR libstdc++/88101 */ +/* { dg-do run } */ struct S { char a; short b; char c; } s1[24], s2[24]; struct T { char a; long long b; char c; struct S d[3]; long long e; char f; } t1, t2; diff --git a/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-6.c b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-6.c new file mode 100644 index 00000000000..db1f00eca73 --- /dev/null +++ b/gcc/testsuite/c-c++-common/torture/builtin-clear-padding-6.c @@ -0,0 +1,28 @@ +/* PR middle-end/115527 */ +/* { dg-do run } */ + +struct T { struct S { double a; signed char b; long c; } d[3]; int e; } t1, t2; + +__attribute__((noipa)) void +foo (struct T *t) +{ + for (int i = 0; i < 3; ++i) + { + t->d[i].a = 1. + 3 * i; + t->d[i].b = 2 + 3 * i; + t->d[i].c = 3 + 3 * i; + } + t->e = 10; +} + +int +main () +{ + __builtin_memset (&t2, -1, sizeof (t2)); + foo (&t1); + foo (&t2); + __builtin_clear_padding (&t2); + if (__builtin_memcmp (&t1, &t2, sizeof (t1))) + __builtin_abort (); + return 0; +}