On Thu, 17 May 2018, Richard Biener wrote:
>
> The following makes use of range-info to improve the basic building
> block of the alias-oracle so we can tell that in
>
> a[0] = 1;
> for (int i = 5; i < 17; ++i)
> a[i] = i;
> a[0] = 2;
>
> the ao_ref for a[i] does not alias the a[0] acceses. Given range-info
> is not always going to improve things over knowledge gained from
> the type size of the access I'm only improving it over information
> gathered from the size.
>
> For the above this allows us to DSE the first store with another
> DSE improvement I'm testing separately.
>
> Bootstrap & regtest in progress on x86_64-unknown-linux-gnu.
I've committed the following sligtly safer with respect to
flexarray - I'll improve it as followup but need to refactor things
a bit for that. I've also adjusted graphite testcases producing
dead data.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2018-05-18 Richard Biener <rguent...@suse.de>
* tree-dfa.c (get_ref_base_and_extent): Use range-info to refine
results when processing array refs with variable index.
* gcc.dg/tree-ssa/ssa-dse-35.c: New testcase.
* gcc.dg/graphite/scop-10.c: Adjust to avoid dead code.
* gcc.dg/graphite/scop-6.c: Likewise.
* gcc.dg/graphite/scop-7.c: Likewise.
* gcc.dg/graphite/scop-8.c: Likewise.
* gcc.dg/graphite/scop-9.c: Likewise.
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-10.c
b/gcc/testsuite/gcc.dg/graphite/scop-10.c
index 20d53510b4e..d04183072f3 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-10.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-10.c
@@ -22,7 +22,7 @@ int toto()
b[i+k] = b[i+k-5] + 2;
}
- return a[3][5] + b[1];
+ return a[3][5] + b[2];
}
/* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-6.c
b/gcc/testsuite/gcc.dg/graphite/scop-6.c
index 1da486a2ddf..9bc1d9f4ccd 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-6.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-6.c
@@ -23,7 +23,7 @@ int toto()
b[i+k] = b[i+k-5] + 2;
}
- return a[3][5] + b[1];
+ return a[3][5] + b[2];
}
/* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-7.c
b/gcc/testsuite/gcc.dg/graphite/scop-7.c
index 2f0a50470e9..f4f3093fcaf 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-7.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-7.c
@@ -23,7 +23,7 @@ int toto()
b[i+k] = b[i+k-5] + 2;
}
- return a[3][5] + b[1];
+ return a[3][5] + b[2];
}
/* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-8.c
b/gcc/testsuite/gcc.dg/graphite/scop-8.c
index 3ceb5d874d6..b06265108c6 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-8.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-8.c
@@ -23,7 +23,7 @@ int toto()
b[i+k] = b[i+k-5] + 2;
}
- return a[3][5] + b[1];
+ return a[3][5] + b[2];
}
/* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-9.c
b/gcc/testsuite/gcc.dg/graphite/scop-9.c
index 93888728b0d..b19291be2f8 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-9.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-9.c
@@ -18,7 +18,7 @@ int toto()
b[i+k] = b[i+k-5] + 2;
}
- return a[3][5] + b[1];
+ return a[3][5] + b[2];
}
/* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-35.c
b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-35.c
new file mode 100644
index 00000000000..1f21670406f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-35.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-dse1-details" } */
+
+int a[256];
+void foo (void)
+{
+ a[0] = 1;
+ for (int i = 5; i < 17; ++i)
+ a[i] = i;
+ a[0] = 2;
+}
+
+/* { dg-final { scan-tree-dump-times "Deleted dead store" 1 "dse1" } } */
Index: gcc/tree-dfa.c
===================================================================
--- gcc/tree-dfa.c (revision 260322)
+++ gcc/tree-dfa.c (working copy)
@@ -529,6 +529,49 @@ get_ref_base_and_extent (tree exp, poly_
/* Remember that we have seen an array ref with a variable
index. */
seen_variable_array_ref = true;
+
+ wide_int min, max;
+ if (TREE_CODE (index) == SSA_NAME
+ && (low_bound = array_ref_low_bound (exp),
+ poly_int_tree_p (low_bound))
+ && (unit_size = array_ref_element_size (exp),
+ TREE_CODE (unit_size) == INTEGER_CST)
+ && get_range_info (index, &min, &max) == VR_RANGE)
+ {
+ poly_offset_int lbound = wi::to_poly_offset (low_bound);
+ /* Try to constrain maxsize with range information. */
+ offset_int omax
+ = offset_int::from (max, TYPE_SIGN (TREE_TYPE (index)));
+ if (known_lt (lbound, omax))
+ {
+ poly_offset_int rmaxsize;
+ rmaxsize = (omax - lbound + 1)
+ * wi::to_offset (unit_size) << LOG2_BITS_PER_UNIT;
+ if (!known_size_p (maxsize)
+ || known_lt (rmaxsize, maxsize))
+ {
+ /* If we know an upper bound below the declared
+ one this is no longer variable. */
+ if (known_size_p (maxsize))
+ seen_variable_array_ref = false;
+ maxsize = rmaxsize;
+ }
+ }
+ /* Try to adjust bit_offset with range information. */
+ offset_int omin
+ = offset_int::from (min, TYPE_SIGN (TREE_TYPE (index)));
+ if (known_le (lbound, omin))
+ {
+ poly_offset_int woffset
+ = wi::sext (omin - lbound,
+ TYPE_PRECISION (TREE_TYPE (index)));
+ woffset *= wi::to_offset (unit_size);
+ woffset <<= LOG2_BITS_PER_UNIT;
+ bit_offset += woffset;
+ if (known_size_p (maxsize))
+ maxsize -= woffset;
+ }
+ }
}
}
break;
