| Summary: | [4.8 Regression] wrong code at -O3 on x86_64-linux-gnu | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Zhendong Su <su> |
| Component: | tree-optimization | Assignee: | Richard Biener <rguenth> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | jakub |
| Priority: | P3 | Keywords: | wrong-code |
| Version: | 6.0 | ||
| Target Milestone: | 4.9.3 | ||
| Host: | Target: | ||
| Build: | Known to work: | 4.9.3, 5.2.0, 6.0 | |
| Known to fail: | 4.9.2, 5.1.0 | Last reconfirmed: | 2015-05-24 00:00:00 |
The testcase can be simplified a bit (I eliminated variable c and moved array a inside main, so it's now local).
struct S
{
int f0;
int f1;
};
int b;
int main ()
{
struct S a[2] = { 0 };
struct S d = { 0, 1 };
for (b = 0; b < 2; b++) {
a[b] = d;
d = a[0];
}
if (d.f1 != 1)
__builtin_abort ();
}
Wrong transformation is made in predictive commoning pass (the program compiled with -O3 -fno-predictive-commoning does not abort). The store d.f1 = a[0].f1; is assumed to be independent of the previous store to a[b] (which is obviously wrong) and it is hoisted out of the loop.
I think the reason is that find_data_references_in_stmt or some related function misenterprets MEM[(struct S[2] *)&a + 4B] as some object that does not alias with MEM[(struct S *)&a]'s SCEV.
By the way, the expression itself looks strange: struct S * should be "a", not "&a".
(Data Dep:
#(Data Ref:
# bb: 3
# stmt: MEM[(struct S *)_4 + 4B] = d$f1_7;
# ref: MEM[(struct S *)_4 + 4B];
# base_object: MEM[(struct S *)&a];
# Access function 0: {4B, +, 8}_1
#)
#(Data Ref:
# bb: 3
# stmt: d$f1_16 = MEM[(struct S[2] *)&a + 4B];
# ref: MEM[(struct S[2] *)&a + 4B];
# base_object: MEM[(struct S[2] *)&a + 4B];
#)
(no dependence)
)
If I scalarize the assignment d = a[0] (I mean, in the source), the bug disappears.
Bah, mine. Author: rguenth Date: Wed May 27 14:20:48 2015 New Revision: 223759 URL: https://gcc.gnu.org/viewcvs?rev=223759&root=gcc&view=rev Log: 2015-05-27 Richard Biener <rguenther@suse.de> PR tree-optimization/66272 Revert parts of 2014-08-15 Richard Biener <rguenther@suse.de> PR tree-optimization/62031 * tree-data-ref.c (dr_analyze_indices): Do not set DR_UNCONSTRAINED_BASE. (dr_may_alias_p): All indirect accesses have to go the formerly DR_UNCONSTRAINED_BASE path. * tree-data-ref.h (struct indices): Remove unconstrained_base member. (DR_UNCONSTRAINED_BASE): Remove. * gcc.dg/torture/pr66272.c: New testcase. Added: trunk/gcc/testsuite/gcc.dg/torture/pr66272.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/tree-data-ref.c trunk/gcc/tree-data-ref.h Fixed on trunk sofar. Author: rguenth Date: Wed Jun 3 07:39:06 2015 New Revision: 224059 URL: https://gcc.gnu.org/viewcvs?rev=224059&root=gcc&view=rev Log: 2015-06-03 Richard Biener <rguenther@suse.de> Backport from mainline 2015-06-02 Richard Biener <rguenther@suse.de> PR debug/65549 * dwarf2out.c (lookup_context_die): New function. (resolve_addr): Avoid forcing a full DIE for the target of a DW_TAG_GNU_call_site during late compilation. Instead create a stub DIE without a type if we have a context DIE present. * g++.dg/lto/pr65549_0.C: New testcase. 2015-06-01 Richard Biener <rguenther@suse.de> PR tree-optimization/66280 * tree-vect-slp.c (vect_detect_hybrid_slp_stmts): Fix pattern def-use walking. * g++.dg/torture/pr66280.C: New testcase. * g++.dg/torture/pr66280-2.C: Likewise. 2015-05-27 Richard Biener <rguenther@suse.de> PR tree-optimization/66272 Revert parts of 2014-08-15 Richard Biener <rguenther@suse.de> PR tree-optimization/62031 * tree-data-ref.c (dr_analyze_indices): Do not set DR_UNCONSTRAINED_BASE. (dr_may_alias_p): All indirect accesses have to go the formerly DR_UNCONSTRAINED_BASE path. * tree-data-ref.h (struct indices): Remove unconstrained_base member. (DR_UNCONSTRAINED_BASE): Remove. * gcc.dg/torture/pr66272.c: New testcase. 2015-05-21 Richard Biener <rguenther@suse.de> PR c++/66211 * match.pd: Guard pattern optimzing (int)(float)int conversions to apply only on GIMPLE. * g++.dg/conversion/pr66211.C: New testcase. * gcc.dg/tree-ssa/forwprop-18.c: Adjust. 2015-05-13 Richard Biener <rguenther@suse.de> PR tree-optimization/66123 * tree-ssa-dom.c (propagate_rhs_into_lhs): Check if we found a taken edge. * gcc.dg/torture/pr66123.c: New testcase. Added: branches/gcc-5-branch/gcc/testsuite/g++.dg/conversion/pr66211.C branches/gcc-5-branch/gcc/testsuite/g++.dg/lto/pr65549_0.C branches/gcc-5-branch/gcc/testsuite/g++.dg/torture/pr66280-2.C branches/gcc-5-branch/gcc/testsuite/g++.dg/torture/pr66280.C branches/gcc-5-branch/gcc/testsuite/gcc.dg/torture/pr66123.c branches/gcc-5-branch/gcc/testsuite/gcc.dg/torture/pr66272.c Modified: branches/gcc-5-branch/gcc/ChangeLog branches/gcc-5-branch/gcc/dwarf2out.c branches/gcc-5-branch/gcc/match.pd branches/gcc-5-branch/gcc/testsuite/ChangeLog branches/gcc-5-branch/gcc/testsuite/gcc.dg/tree-ssa/forwprop-18.c branches/gcc-5-branch/gcc/tree-data-ref.c branches/gcc-5-branch/gcc/tree-data-ref.h branches/gcc-5-branch/gcc/tree-ssa-dom.c branches/gcc-5-branch/gcc/tree-vect-slp.c Author: rguenth Date: Wed Jun 3 11:03:26 2015 New Revision: 224072 URL: https://gcc.gnu.org/viewcvs?rev=224072&root=gcc&view=rev Log: 2015-06-03 Richard Biener <rguenther@suse.de> Backport from mainline 2015-05-26 Michael Matz <matz@suse.de> PR middle-end/66251 * tree-vect-stmts.c (vect_create_vectorized_demotion_stmts): Always set STMT_VINFO_VEC_STMT, also with SLP. * gcc.dg/vect/pr66251.c: New test. 2015-05-22 Richard Biener <rguenther@suse.de> PR tree-optimization/66251 * tree-vect-stmts.c (vectorizable_conversion): Properly set STMT_VINFO_VEC_STMT even for the SLP case. * gfortran.fortran-torture/compile/pr66251.f90: New testcase. 2015-05-27 Richard Biener <rguenther@suse.de> PR tree-optimization/66272 Revert parts of 2014-08-15 Richard Biener <rguenther@suse.de> PR tree-optimization/62031 * tree-data-ref.c (dr_analyze_indices): Do not set DR_UNCONSTRAINED_BASE. (dr_may_alias_p): All indirect accesses have to go the formerly DR_UNCONSTRAINED_BASE path. * tree-data-ref.h (struct indices): Remove unconstrained_base member. (DR_UNCONSTRAINED_BASE): Remove. * gcc.dg/torture/pr66272.c: New testcase. 2015-05-13 Richard Biener <rguenther@suse.de> PR tree-optimization/66123 * tree-ssa-dom.c (propagate_rhs_into_lhs): Check if we found a taken edge. * gcc.dg/torture/pr66123.c: New testcase. 2015-06-02 Richard Biener <rguenther@suse.de> PR debug/65549 * dwarf2out.c (lookup_context_die): New function. (resolve_addr): Avoid forcing a full DIE for the target of a DW_TAG_GNU_call_site during late compilation. Instead create a stub DIE without a type if we have a context DIE present. * g++.dg/lto/pr65549_0.C: New testcase. 2015-03-23 Richard Biener <rguenther@suse.de> PR tree-optimization/65518 * tree-vect-stmts.c (vectorizable_load): Reject single-element interleaving cases we generate absymal code for. * gcc.dg/vect/pr65518.c: New testcase. Added: branches/gcc-4_9-branch/gcc/testsuite/g++.dg/lto/pr65549_0.C branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/torture/pr66123.c branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/torture/pr66272.c branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/vect/pr65518.c branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/vect/pr66251.c branches/gcc-4_9-branch/gcc/testsuite/gfortran.fortran-torture/compile/pr66251.f90 Modified: branches/gcc-4_9-branch/gcc/ChangeLog branches/gcc-4_9-branch/gcc/dwarf2out.c branches/gcc-4_9-branch/gcc/testsuite/ChangeLog branches/gcc-4_9-branch/gcc/tree-data-ref.c branches/gcc-4_9-branch/gcc/tree-data-ref.h branches/gcc-4_9-branch/gcc/tree-ssa-dom.c branches/gcc-4_9-branch/gcc/tree-vect-stmts.c Author: rguenth Date: Wed Jun 3 13:50:11 2015 New Revision: 224081 URL: https://gcc.gnu.org/viewcvs?rev=224081&root=gcc&view=rev Log: 2015-06-03 Richard Biener <rguenther@suse.de> Backport from mainline 2015-05-26 Michael Matz <matz@suse.de> PR middle-end/66251 * tree-vect-stmts.c (vect_create_vectorized_demotion_stmts): Always set STMT_VINFO_VEC_STMT, also with SLP. * gcc.dg/vect/pr66251.c: New test. 2015-05-22 Richard Biener <rguenther@suse.de> PR tree-optimization/66251 * tree-vect-stmts.c (vectorizable_conversion): Properly set STMT_VINFO_VEC_STMT even for the SLP case. * gfortran.fortran-torture/compile/pr66251.f90: New testcase. 2015-03-23 Richard Biener <rguenther@suse.de> PR tree-optimization/65518 * tree-vect-stmts.c (vectorizable_load): Reject single-element interleaving cases we generate absymal code for. * gcc.dg/vect/pr65518.c: New testcase. 2015-05-13 Richard Biener <rguenther@suse.de> PR tree-optimization/66123 * tree-ssa-dom.c (propagate_rhs_into_lhs): Check if we found a taken edge. * gcc.dg/torture/pr66123.c: New testcase. 2015-05-27 Richard Biener <rguenther@suse.de> PR tree-optimization/66272 Revert parts of 2014-08-15 Richard Biener <rguenther@suse.de> PR tree-optimization/62031 * tree-data-ref.c (dr_analyze_indices): Do not set DR_UNCONSTRAINED_BASE. (dr_may_alias_p): All indirect accesses have to go the formerly DR_UNCONSTRAINED_BASE path. * tree-data-ref.h (struct indices): Remove unconstrained_base member. (DR_UNCONSTRAINED_BASE): Remove. * gcc.dg/torture/pr66272.c: New testcase. Added: branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/torture/pr66123.c branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/torture/pr66272.c branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/vect/pr65518.c branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/vect/pr66251.c branches/gcc-4_8-branch/gcc/testsuite/gfortran.fortran-torture/compile/pr66251.f90 Modified: branches/gcc-4_8-branch/gcc/ChangeLog branches/gcc-4_8-branch/gcc/testsuite/ChangeLog branches/gcc-4_8-branch/gcc/tree-data-ref.c branches/gcc-4_8-branch/gcc/tree-data-ref.h branches/gcc-4_8-branch/gcc/tree-ssa-dom.c branches/gcc-4_8-branch/gcc/tree-vect-stmts.c Fixed. |
The current gcc trunk miscompiles the following code on x86_64-linux at -O3 in both 32-bit and 64-bit modes. It also affects gcc 5.1.x and 4.9.2 (but not 4.9.0 and I didn't check 4.9.1). $ gcc-trunk -v Using built-in specs. COLLECT_GCC=gcc-trunk COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/lto-wrapper Target: x86_64-unknown-linux-gnu Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk --enable-languages=c,c++ --disable-werror --enable-multilib Thread model: posix gcc version 6.0.0 20150524 (experimental) [trunk revision 223630] (GCC) $ $ gcc-trunk -O2 small.c; ./a.out $ gcc-4.9.0 -O3 small.c; ./a.out $ $ gcc-trunk -O3 small.c $ ./a.out Aborted (core dumped) $ gcc-4.9.2 -O3 small.c $ ./a.out Aborted (core dumped) $ gcc-5.1.0 -O3 small.c $ ./a.out Aborted (core dumped) $ ---------------------------- struct S { int f0; int f1; } a[2], c; int b; int main () { struct S d = { 0, 1 }; for (b = 0; b < 2; b++) { a[b] = d; c = d = a[0]; } if (c.f1 != 1) __builtin_abort (); return 0; }