Hello,
This should have the changes you all asked for! Let me know if I
missed anything!
Thank you,
Matthew Beliveau
On Tue, Aug 13, 2019 at 5:15 AM Richard Biener
<richard.guent...@gmail.com> wrote:
>
> On Tue, Aug 13, 2019 at 10:18 AM Richard Sandiford
> <richard.sandif...@arm.com> wrote:
> >
> > Thanks for doing this.
> >
> > Matthew Beliveau <mbeli...@redhat.com> writes:
> > > diff --git gcc/tree-ssa-dse.c gcc/tree-ssa-dse.c
> > > index 5b7c4fc6d1a..dcaeb8edbfe 100644
> > > --- gcc/tree-ssa-dse.c
> > > +++ gcc/tree-ssa-dse.c
> > > @@ -628,11 +628,8 @@ dse_optimize_redundant_stores (gimple *stmt)
> > > tree fndecl;
> > > if ((is_gimple_assign (use_stmt)
> > > && gimple_vdef (use_stmt)
> > > - && ((gimple_assign_rhs_code (use_stmt) == CONSTRUCTOR
> > > - && CONSTRUCTOR_NELTS (gimple_assign_rhs1 (use_stmt)) == 0
> > > - && !gimple_clobber_p (stmt))
> > > - || (gimple_assign_rhs_code (use_stmt) == INTEGER_CST
> > > - && integer_zerop (gimple_assign_rhs1 (use_stmt)))))
> > > + && initializer_zerop (gimple_op (use_stmt, 1), NULL)
> > > + && !gimple_clobber_p (stmt))
> > > || (gimple_call_builtin_p (use_stmt, BUILT_IN_NORMAL)
> > > && (fndecl = gimple_call_fndecl (use_stmt)) != NULL
> > > && (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_MEMSET
> > > @@ -1027,15 +1024,13 @@ dse_dom_walker::dse_optimize_stmt
> > > (gimple_stmt_iterator *gsi)
> > > {
> > > bool by_clobber_p = false;
> > >
> > > - /* First see if this store is a CONSTRUCTOR and if there
> > > - are subsequent CONSTRUCTOR stores which are totally
> > > - subsumed by this statement. If so remove the subsequent
> > > - CONSTRUCTOR store.
> > > + /* Check if this store initalizes zero, or some aggregate of zeros,
> > > + and check if there are subsequent stores which are subsumed by this
> > > + statement. If so, remove the subsequent store.
> > >
> > > This will tend to make fewer calls into memset with longer
> > > arguments. */
> > > - if (gimple_assign_rhs_code (stmt) == CONSTRUCTOR
> > > - && CONSTRUCTOR_NELTS (gimple_assign_rhs1 (stmt)) == 0
> > > + if (initializer_zerop (gimple_op (stmt, 1), NULL)
> > > && !gimple_clobber_p (stmt))
> > > dse_optimize_redundant_stores (stmt);
> > >
> >
> > In addition to Jeff's comment, the original choice of gimple_assign_rhs1
> > is the preferred way to write this (applies to both hunks).
>
> And the !gimple_clobber_p test is now redundant.
>
> > Richard
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2019-08-13 Matthew Beliveau <mbeli...@redhat.com>
* tree-ssa-dse.c (dse_optimize_redundant_stores): Improved check to
catch more redundant zero initialization cases.
(dse_dom_walker::dse_optimize_stmt): Likewise.
* gcc.dg/tree-ssa/redundant-assign-zero-1.c: New test.
* gcc.dg/tree-ssa/redundant-assign-zero-2.c: New test.
diff --git gcc/testsuite/gcc.dg/tree-ssa/redundant-assign-zero-1.c gcc/testsuite/gcc.dg/tree-ssa/redundant-assign-zero-1.c
new file mode 100644
index 00000000000..b8d01d1644b
--- /dev/null
+++ gcc/testsuite/gcc.dg/tree-ssa/redundant-assign-zero-1.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-dse-details" } */
+
+void blah (char *);
+
+void bar ()
+{
+ char a[256] = "";
+ a[3] = 0;
+ blah (a);
+}
+
+/* { dg-final { scan-tree-dump-times "Deleted redundant store" 1 "dse1"} } */
diff --git gcc/testsuite/gcc.dg/tree-ssa/redundant-assign-zero-2.c gcc/testsuite/gcc.dg/tree-ssa/redundant-assign-zero-2.c
new file mode 100644
index 00000000000..8cefa6f0cb7
--- /dev/null
+++ gcc/testsuite/gcc.dg/tree-ssa/redundant-assign-zero-2.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-dse-details" } */
+
+#include <string.h>
+
+void blahd (double *);
+
+void fubar ()
+{
+ double d;
+ double *x = &d;
+
+ memset (&d, 0 , sizeof d);
+ *x = 0.0;
+ blahd (x);
+}
+
+/* { dg-final { scan-tree-dump-times "Deleted redundant store" 1 "dse1"} } */
diff --git gcc/tree-ssa-dse.c gcc/tree-ssa-dse.c
index 5b7c4fc6d1a..14b66228e1e 100644
--- gcc/tree-ssa-dse.c
+++ gcc/tree-ssa-dse.c
@@ -628,11 +628,7 @@ dse_optimize_redundant_stores (gimple *stmt)
tree fndecl;
if ((is_gimple_assign (use_stmt)
&& gimple_vdef (use_stmt)
- && ((gimple_assign_rhs_code (use_stmt) == CONSTRUCTOR
- && CONSTRUCTOR_NELTS (gimple_assign_rhs1 (use_stmt)) == 0
- && !gimple_clobber_p (stmt))
- || (gimple_assign_rhs_code (use_stmt) == INTEGER_CST
- && integer_zerop (gimple_assign_rhs1 (use_stmt)))))
+ && initializer_zerop (gimple_assign_rhs1 (use_stmt)))
|| (gimple_call_builtin_p (use_stmt, BUILT_IN_NORMAL)
&& (fndecl = gimple_call_fndecl (use_stmt)) != NULL
&& (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_MEMSET
@@ -1027,16 +1023,10 @@ dse_dom_walker::dse_optimize_stmt (gimple_stmt_iterator *gsi)
{
bool by_clobber_p = false;
- /* First see if this store is a CONSTRUCTOR and if there
- are subsequent CONSTRUCTOR stores which are totally
- subsumed by this statement. If so remove the subsequent
- CONSTRUCTOR store.
-
- This will tend to make fewer calls into memset with longer
- arguments. */
- if (gimple_assign_rhs_code (stmt) == CONSTRUCTOR
- && CONSTRUCTOR_NELTS (gimple_assign_rhs1 (stmt)) == 0
- && !gimple_clobber_p (stmt))
+ /* Check if this statement stores zero to a memory location,
+ and if there is a subsequent store of zero to the same
+ memory location. If so, remove the subsequent store. */
+ if (initializer_zerop (gimple_assign_rhs1 (stmt)))
dse_optimize_redundant_stores (stmt);
/* Self-assignments are zombies. */
