From fbd28bc3b2c3394db09577ff2f5a594d50c75b2c Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Thu, 14 Mar 2013 10:13:36 +0100
Subject: [PATCH] re PR tree-optimization/53265 (Warn when undefined behavior
implies smaller iteration count)
PR tree-optimization/53265
* common.opt (Waggressive-loop-optimizations): New option.
* tree-ssa-loop-niter.c: Include tree-pass.h.
(do_warn_aggressive_loop_optimizations): New function.
(record_estimate): Call it. Don't add !is_exit bounds to loop->bounds
if number_of_latch_executions returned constant.
(estimate_numbers_of_iterations_loop): Call number_of_latch_executions
early. If number_of_latch_executions returned constant, set
nb_iterations_upper_bound back to it.
* cfgloop.h (struct loop): Add warned_aggressive_loop_optimizations
field.
* Makefile.in (tree-ssa-loop-niter.o): Depend on $(TREE_PASS_H).
* doc/invoke.texi (-Wno-aggressive-loop-optimizations): Document.
* gcc.dg/pr53265.c: New test.
* gcc.dg/torture/pr49518.c: Add -Wno-aggressive-loop-optimizations
to dg-options.
* g++.dg/opt/longbranch2.C (EBCOTLut): Double sizes of a2 and a3
arrays.
* gcc.dg/tree-ssa/cunroll-10.c (main): Rename to foo. Add argument
n, use it as high bound instead of 4.
* unwind-dw2.c (execute_cfa_program): Avoid
-Waggressive-array-optimizations warnings for DW_CFA_GNU_window_save
on targets with DWARF_FRAME_REGISTERS < 32.
* testsuite/libmudflap.c/fail37-frag.c: Add optimization barrier.
From-SVN: r196650
---
gcc/ChangeLog | 14 ++
gcc/Makefile.in | 2 +-
gcc/cfgloop.h | 4 +
gcc/common.opt | 4 +
gcc/doc/invoke.texi | 9 +-
gcc/testsuite/ChangeLog | 11 ++
gcc/testsuite/g++.dg/opt/longbranch2.C | 4 +-
gcc/testsuite/gcc.dg/pr53265.c | 156 ++++++++++++++++++
gcc/testsuite/gcc.dg/torture/pr49518.c | 1 +
gcc/testsuite/gcc.dg/tree-ssa/cunroll-10.c | 5 +-
gcc/tree-ssa-loop-niter.c | 61 ++++++-
libgcc/ChangeLog | 7 +
libgcc/unwind-dw2.c | 11 +-
libmudflap/ChangeLog | 5 +
.../testsuite/libmudflap.c/fail37-frag.c | 6 +-
15 files changed, 286 insertions(+), 14 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/pr53265.c
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 78b3616196c0..c403ca72d6dc 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,19 @@
2013-03-14 Jakub Jelinek <jakub@redhat.com>
+ PR tree-optimization/53265
+ * common.opt (Waggressive-loop-optimizations): New option.
+ * tree-ssa-loop-niter.c: Include tree-pass.h.
+ (do_warn_aggressive_loop_optimizations): New function.
+ (record_estimate): Call it. Don't add !is_exit bounds to loop->bounds
+ if number_of_latch_executions returned constant.
+ (estimate_numbers_of_iterations_loop): Call number_of_latch_executions
+ early. If number_of_latch_executions returned constant, set
+ nb_iterations_upper_bound back to it.
+ * cfgloop.h (struct loop): Add warned_aggressive_loop_optimizations
+ field.
+ * Makefile.in (tree-ssa-loop-niter.o): Depend on $(TREE_PASS_H).
+ * doc/invoke.texi (-Wno-aggressive-loop-optimizations): Document.
+
* config/aarch64/t-aarch64-linux (MULTARCH_DIRNAME): Remove.
(MULTILIB_OSDIRNAMES): Set.
* genmultilib: If defaultosdirname doesn't start with :: , set
diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 6d9ca1b47e4e..54ea04f644a1 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -2446,7 +2446,7 @@ tree-ssa-loop-niter.o : tree-ssa-loop-niter.c $(TREE_FLOW_H) $(CONFIG_H) \
$(SYSTEM_H) $(TREE_H) $(TM_P_H) $(CFGLOOP_H) $(PARAMS_H) \
$(TREE_INLINE_H) $(DIAGNOSTIC_H) $(TM_H) coretypes.h dumpfile.h \
$(DIAGNOSTIC_CORE_H) $(FLAGS_H) $(TREE_DATA_REF_H) \
- $(BASIC_BLOCK_H) $(GGC_H) intl.h $(GIMPLE_PRETTY_PRINT_H)
+ $(BASIC_BLOCK_H) $(GGC_H) intl.h $(GIMPLE_PRETTY_PRINT_H) $(TREE_PASS_H)
tree-ssa-loop-ivcanon.o : tree-ssa-loop-ivcanon.c $(TREE_FLOW_H) $(CONFIG_H) \
$(SYSTEM_H) $(TREE_H) $(TM_P_H) $(CFGLOOP_H) $(PARAMS_H) \
$(TREE_INLINE_H) $(DIAGNOSTIC_H) $(TM_H) coretypes.h \
diff --git a/gcc/cfgloop.h b/gcc/cfgloop.h
index 0b2af724e100..01cef519a0ca 100644
--- a/gcc/cfgloop.h
+++ b/gcc/cfgloop.h
@@ -159,6 +159,10 @@ struct GTY ((chain_next ("%h.next"))) loop {
/* True if the loop can be parallel. */
bool can_be_parallel;
+ /* True if -Waggressive-loop-optimizations warned about this loop
+ already. */
+ bool warned_aggressive_loop_optimizations;
+
/* An integer estimation of the number of iterations. Estimate_state
describes what is the state of the estimation. */
enum loop_estimation estimate_state;
diff --git a/gcc/common.opt b/gcc/common.opt
index 3c7b4153846d..bdbd3b6cd9ea 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -505,6 +505,10 @@ Waggregate-return
Common Var(warn_aggregate_return) Warning
Warn about returning structures, unions or arrays
+Waggressive-loop-optimizations
+Common Var(warn_aggressive_loop_optimizations) Init(1) Warning
+Warn if a loop with constant number of iterations triggers undefined behavior
+
Warray-bounds
Common Var(warn_array_bounds) Warning
Warn if an array is accessed out of bounds
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 7927c6f2226a..9273d7d7cbdb 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -232,7 +232,8 @@ Objective-C and Objective-C++ Dialects}.
@xref{Warning Options,,Options to Request or Suppress Warnings}.
@gccoptlist{-fsyntax-only -fmax-errors=@var{n} -Wpedantic @gol
-pedantic-errors @gol
--w -Wextra -Wall -Waddress -Waggregate-return -Warray-bounds @gol
+-w -Wextra -Wall -Waddress -Waggregate-return @gol
+-Waggressive-loop-optimizations -Warray-bounds @gol
-Wno-attributes -Wno-builtin-macro-redefined @gol
-Wc++-compat -Wc++11-compat -Wcast-align -Wcast-qual @gol
-Wchar-subscripts -Wclobbered -Wcomment @gol
@@ -4423,6 +4424,12 @@ Warn if any functions that return structures or unions are defined or
called. (In languages where you can return an array, this also elicits
a warning.)
+@item -Wno-aggressive-loop-optimizations
+@opindex Wno-aggressive-loop-optimizations
+@opindex Waggressive-loop-optimizations
+Warn if in a loop with constant number of iterations the compiler detects
+undefined behavior in some statement during one or more of the iterations.
+
@item -Wno-attributes
@opindex Wno-attributes
@opindex Wattributes
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 231ceb5bd0ac..19fab0e0d5ba 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,14 @@
+2013-03-14 Jakub Jelinek <jakub@redhat.com>
+
+ PR tree-optimization/53265
+ * gcc.dg/pr53265.c: New test.
+ * gcc.dg/torture/pr49518.c: Add -Wno-aggressive-loop-optimizations
+ to dg-options.
+ * g++.dg/opt/longbranch2.C (EBCOTLut): Double sizes of a2 and a3
+ arrays.
+ * gcc.dg/tree-ssa/cunroll-10.c (main): Rename to foo. Add argument
+ n, use it as high bound instead of 4.
+
2013-03-13 Oleg Endo <olegendo@gcc.gnu.org>
PR target/49880
diff --git a/gcc/testsuite/g++.dg/opt/longbranch2.C b/gcc/testsuite/g++.dg/opt/longbranch2.C
index de63f697fcff..4a8d5eef735f 100644
--- a/gcc/testsuite/g++.dg/opt/longbranch2.C
+++ b/gcc/testsuite/g++.dg/opt/longbranch2.C
@@ -15,8 +15,8 @@ public:
class EBCOTLut : public JKeeper {
unsigned char a1[1<<8];
- unsigned char a2[1<<8];
- unsigned char a3[1<<8];
+ unsigned char a2[1<<9];
+ unsigned char a3[1<<9];
long a4[1<<9];
public:
EBCOTLut(void);
diff --git a/gcc/testsuite/gcc.dg/pr53265.c b/gcc/testsuite/gcc.dg/pr53265.c
new file mode 100644
index 000000000000..c60a736a9279
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr53265.c
@@ -0,0 +1,156 @@
+/* PR tree-optimization/53265 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -Wall" } */
+
+void bar (void *);
+int baz (int);
+
+void
+fn1 (void)
+{
+ unsigned int a[128];
+ int i;
+
+ for (i = 0; i < 128; ++i) /* { dg-message "note: containing loop" } */
+ a[i] = i * 0x02000001; /* { dg-warning "invokes undefined behavior" } */
+ bar (a);
+}
+
+void
+fn2 (void)
+{
+ unsigned long long a[128];
+ int i;
+
+ for (i = 0; i < 128; i++) /* { dg-message "note: containing loop" } */
+ a[i] = (i + 1LL) * 0x0123456789ABCDEFLL; /* { dg-warning "invokes undefined behavior" } */
+ bar (a);
+}
+
+void
+fn3 (void)
+{
+ unsigned char a[16], b[16], c[16];
+ int i;
+
+ bar (b);
+ for (i = 0; i < (int) (sizeof (a) / sizeof (a[0])); i++) /* { dg-message "note: containing loop" } */
+ {
+ c[i + 8] = b[i]; /* { dg-warning "invokes undefined behavior" } */
+ a[i + 8] = b[i + 8];
+ }
+ bar (a);
+ bar (c);
+}
+
+void
+fn4 (void)
+{
+ unsigned int *a[32], *o, i;
+
+ bar (a);
+ for (i = 0; i <= sizeof (a) / sizeof (a[0]); i++) /* { dg-message "note: containing loop" "" { xfail *-*-* } } */
+ {
+ o = a[i]; /* { dg-warning "invokes undefined behavior" "" { xfail *-*-* } } */
+ bar (o);
+ }
+}
+
+void
+fn5 (void)
+{
+ unsigned short a[23940];
+ unsigned int b[1140];
+ int j;
+
+ bar (b);
+ for (j = 0; j < 1140; j++) /* { dg-message "note: containing loop" } */
+ a[23940 + j - 950] = b[j]; /* { dg-warning "invokes undefined behavior" } */
+ bar (a);
+}
+
+void
+fn6 (void)
+{
+ double a[4][3], b[12];
+ int i;
+ bar (b);
+ for (i = 0; i < 12; i++) /* { dg-message "note: containing loop" } */
+ a[0][i] = b[i] / 10000.0; /* { dg-warning "invokes undefined behavior" } */
+ bar (a);
+}
+
+void
+fn7 (void)
+{
+ int a[16], b, c;
+ bar (a);
+ for (b = a[c = 0]; c < 16; b = a[++c]) /* { dg-warning "invokes undefined behavior" "" { xfail *-*-* } } */
+ baz (b);
+}
+
+/* { dg-message "note: containing loop" "" { xfail *-*-* } 88 } */
+
+const void *va, *vb, *vc, *vd, *ve;
+const void *vf[4];
+void
+fn8 (void)
+{
+ unsigned long i;
+ vf[0] = va; vf[1] = vb; vf[2] = vc; vf[3] = vd;
+ for (i = 0; i < (sizeof (vf) / sizeof (vf[0])); i++)
+ if (!vf[i])
+ vf[i] = ve;
+}
+
+int wa, wb[53][5], wc[53][5];
+
+void
+fn9 (void)
+{
+ int i, j, k;
+ for (i = 0; i < 53; i++)
+ for (j = 16 / (((wa & 1) != 0) ? 8 : 4); j > 0; j--)
+ {
+ int d = 1;
+ if (wb[i][j] == 0 || wc[i][1] != 0)
+ continue;
+ for (k = 0; k < j; k++)
+ if (wc[i + k][1])
+ {
+ d = 0;
+ break;
+ }
+ if (!d)
+ continue;
+ wc[i][j] = baz (0);
+ }
+}
+
+int xa[18];
+
+void
+fn10 (void)
+{
+ int i;
+ for (i = 16; i < 32; i++) /* { dg-message "note: containing loop" } */
+ xa[i] = 26; /* { dg-warning "invokes undefined behavior" } */
+}
+
+__attribute__((noinline)) static void
+fn11 (int x)
+{
+ int i = 1;
+ if (x > 1)
+ do
+ baz (i);
+ while (++i != x); /* { dg-bogus "invokes undefined behavior" } */
+}
+
+void
+fn12 (void)
+{
+ fn11 (1);
+ fn11 (1);
+ fn11 (1);
+}
diff --git a/gcc/testsuite/gcc.dg/torture/pr49518.c b/gcc/testsuite/gcc.dg/torture/pr49518.c
index 84a10fbbeebe..55761fd6108b 100644
--- a/gcc/testsuite/gcc.dg/torture/pr49518.c
+++ b/gcc/testsuite/gcc.dg/torture/pr49518.c
@@ -1,4 +1,5 @@
/* { dg-do compile } */
+/* { dg-options "-Wno-aggressive-loop-optimizations" } */
int a, b;
struct S { unsigned int s, t, u; } c, d = { 0, 1, 0 };
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cunroll-10.c b/gcc/testsuite/gcc.dg/tree-ssa/cunroll-10.c
index 7893565918a6..f2cd904efc61 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/cunroll-10.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/cunroll-10.c
@@ -2,10 +2,11 @@
/* { dg-options "-O3 -Warray-bounds -fdump-tree-cunroll-details" } */
int a[3];
int b[4];
-main()
+int
+foo (int n)
{
int i;
- for (i=0;i<4;i++)
+ for (i=0;i<n;i++)
if (b[i]==2)
a[i]++;
}
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index ba06b0c69367..bcd4317f3904 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -37,6 +37,7 @@ along with GCC; see the file COPYING3. If not see
#include "flags.h"
#include "diagnostic-core.h"
#include "tree-inline.h"
+#include "tree-pass.h"
#define SWAP(X, Y) do { affine_iv *tmp = (X); (X) = (Y); (Y) = tmp; } while (0)
@@ -2525,6 +2526,40 @@ record_niter_bound (struct loop *loop, double_int i_bound, bool realistic,
loop->nb_iterations_estimate = loop->nb_iterations_upper_bound;
}
+/* Emit a -Waggressive-loop-optimizations warning if needed. */
+
+static void
+do_warn_aggressive_loop_optimizations (struct loop *loop,
+ double_int i_bound, gimple stmt)
+{
+ /* Don't warn if the loop doesn't have known constant bound. */
+ if (!loop->nb_iterations
+ || TREE_CODE (loop->nb_iterations) != INTEGER_CST
+ || !warn_aggressive_loop_optimizations
+ /* To avoid warning multiple times for the same loop,
+ only start warning when we preserve loops. */
+ || (cfun->curr_properties & PROP_loops) == 0
+ /* Only warn once per loop. */
+ || loop->warned_aggressive_loop_optimizations
+ /* Only warn if undefined behavior gives us lower estimate than the
+ known constant bound. */
+ || i_bound.ucmp (tree_to_double_int (loop->nb_iterations)) >= 0
+ /* And undefined behavior happens unconditionally. */
+ || !dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (stmt)))
+ return;
+
+ edge e = single_exit (loop);
+ if (e == NULL)
+ return;
+
+ gimple estmt = last_stmt (e->src);
+ warning_at (gimple_location (stmt), OPT_Waggressive_loop_optimizations,
+ "iteration %E invokes undefined behavior",
+ double_int_to_tree (TREE_TYPE (loop->nb_iterations), i_bound));
+ inform (gimple_location (estmt), "containing loop");
+ loop->warned_aggressive_loop_optimizations = true;
+}
+
/* Records that AT_STMT is executed at most BOUND + 1 times in LOOP. IS_EXIT
is true if the loop is exited immediately after STMT, and this exit
is taken at last when the STMT is executed BOUND + 1 times.
@@ -2560,8 +2595,12 @@ record_estimate (struct loop *loop, tree bound, double_int i_bound,
return;
/* If we have a guaranteed upper bound, record it in the appropriate
- list. */
- if (upper)
+ list, unless this is an !is_exit bound (i.e. undefined behavior in
+ at_stmt) in a loop with known constant number of iterations. */
+ if (upper
+ && (is_exit
+ || loop->nb_iterations == NULL_TREE
+ || TREE_CODE (loop->nb_iterations) != INTEGER_CST))
{
struct nb_iter_bound *elt = ggc_alloc_nb_iter_bound ();
@@ -2591,6 +2630,8 @@ record_estimate (struct loop *loop, tree bound, double_int i_bound,
if (i_bound.ult (delta))
return;
+ if (upper && !is_exit)
+ do_warn_aggressive_loop_optimizations (loop, i_bound, at_stmt);
record_niter_bound (loop, i_bound, realistic, upper);
}
@@ -3311,6 +3352,11 @@ estimate_numbers_of_iterations_loop (struct loop *loop)
/* Force estimate compuation but leave any existing upper bound in place. */
loop->any_estimate = false;
+ /* Ensure that loop->nb_iterations is computed if possible. If it turns out
+ to be constant, we avoid undefined behavior implied bounds and instead
+ diagnose those loops with -Waggressive-loop-optimizations. */
+ number_of_latch_executions (loop);
+
exits = get_loop_exit_edges (loop);
likely_exit = single_likely_exit (loop);
FOR_EACH_VEC_ELT (exits, i, ex)
@@ -3345,6 +3391,17 @@ estimate_numbers_of_iterations_loop (struct loop *loop)
bound = gcov_type_to_double_int (nit);
record_niter_bound (loop, bound, true, false);
}
+
+ /* If we know the exact number of iterations of this loop, try to
+ not break code with undefined behavior by not recording smaller
+ maximum number of iterations. */
+ if (loop->nb_iterations
+ && TREE_CODE (loop->nb_iterations) == INTEGER_CST)
+ {
+ loop->any_upper_bound = true;
+ loop->nb_iterations_upper_bound
+ = tree_to_double_int (loop->nb_iterations);
+ }
}
/* Sets NIT to the estimated number of executions of the latch of the
diff --git a/libgcc/ChangeLog b/libgcc/ChangeLog
index 61f5cc07694a..aa10774ba987 100644
--- a/libgcc/ChangeLog
+++ b/libgcc/ChangeLog
@@ -1,3 +1,10 @@
+2013-03-14 Jakub Jelinek <jakub@redhat.com>
+
+ PR tree-optimization/53265
+ * unwind-dw2.c (execute_cfa_program): Avoid
+ -Waggressive-array-optimizations warnings for DW_CFA_GNU_window_save
+ on targets with DWARF_FRAME_REGISTERS < 32.
+
2013-03-13 Oleg Endo <olegendo@gcc.gnu.org>
PR target/49880
diff --git a/libgcc/unwind-dw2.c b/libgcc/unwind-dw2.c
index 101a828b556d..80de5ab1894b 100644
--- a/libgcc/unwind-dw2.c
+++ b/libgcc/unwind-dw2.c
@@ -1128,11 +1128,12 @@ execute_cfa_program (const unsigned char *insn_ptr,
case DW_CFA_GNU_window_save:
/* ??? Hardcoded for SPARC register window configuration. */
- for (reg = 16; reg < 32; ++reg)
- {
- fs->regs.reg[reg].how = REG_SAVED_OFFSET;
- fs->regs.reg[reg].loc.offset = (reg - 16) * sizeof (void *);
- }
+ if (DWARF_FRAME_REGISTERS >= 32)
+ for (reg = 16; reg < 32; ++reg)
+ {
+ fs->regs.reg[reg].how = REG_SAVED_OFFSET;
+ fs->regs.reg[reg].loc.offset = (reg - 16) * sizeof (void *);
+ }
break;
case DW_CFA_GNU_args_size:
diff --git a/libmudflap/ChangeLog b/libmudflap/ChangeLog
index 1872b2ebc4b6..6e0d65c2fb79 100644
--- a/libmudflap/ChangeLog
+++ b/libmudflap/ChangeLog
@@ -1,3 +1,8 @@
+2013-03-14 Jakub Jelinek <jakub@redhat.com>
+
+ PR tree-optimization/53265
+ * testsuite/libmudflap.c/fail37-frag.c: Add optimization barrier.
+
2013-02-03 Richard Sandiford <rdsandiford@googlemail.com>
Update copyright years.
diff --git a/libmudflap/testsuite/libmudflap.c/fail37-frag.c b/libmudflap/testsuite/libmudflap.c/fail37-frag.c
index 41ce4b91e05c..38dbde56a814 100644
--- a/libmudflap/testsuite/libmudflap.c/fail37-frag.c
+++ b/libmudflap/testsuite/libmudflap.c/fail37-frag.c
@@ -13,7 +13,11 @@ main ()
{
int i;
for (i = 0; i < 5; i++)
- x.s[i].f = 0;
+ {
+ /* Optimization barrier. Prevent gcc from seeing the undefined behavior. */
+ __asm ("" : "+r" (i));
+ x.s[i].f = 0;
+ }
exit (0);
}
/* { dg-output "mudflap violation 1.*" } */
--
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