From d1753b4be981fcb176f56b6ed45f7dbe1177d641 Mon Sep 17 00:00:00 2001
From: Siddhesh Poyarekar <siddhesh@gotplt.org>
Date: Mon, 15 Nov 2021 23:03:13 +0530
Subject: [PATCH] gimple-fold: Transform stp*cpy_chk to str*cpy directly
Avoid going through another folding cycle and use the ignore flag to
directly transform BUILT_IN_STPCPY_CHK to BUILT_IN_STRCPY when set,
likewise for BUILT_IN_STPNCPY_CHK to BUILT_IN_STPNCPY.
Dump the transformation in dump_file so that we can verify in tests that
the direct transformation actually happened.
gcc/ChangeLog:
* gimple-fold.c (dump_transformation): New function.
(gimple_fold_builtin_stxcpy_chk,
gimple_fold_builtin_stxncpy_chk): Use it. Simplify to
BUILT_IN_STRNCPY if return value is not used.
gcc/testsuite/ChangeLog:
* gcc.dg/fold-stringops-1.c: New test.
Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>
---
gcc/gimple-fold.c | 55 ++++++++++++++++---------
gcc/testsuite/gcc.dg/fold-stringops-1.c | 23 +++++++++++
2 files changed, 58 insertions(+), 20 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/fold-stringops-1.c
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 6e25a7c05dbe..2e92efa7f61e 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -3088,6 +3088,16 @@ gimple_fold_builtin_memory_chk (gimple_stmt_iterator *gsi,
return true;
}
+/* Print a message in the dump file recording transformation of FROM to TO. */
+
+static void
+dump_transformation (gcall *from, gcall *to)
+{
+ if (dump_enabled_p ())
+ dump_printf_loc (MSG_OPTIMIZED_LOCATIONS, from, "simplified %T to %T\n",
+ gimple_call_fn (from), gimple_call_fn (to));
+}
+
/* Fold a call to the __st[rp]cpy_chk builtin.
DEST, SRC, and SIZE are the arguments to the call.
IGNORE is true if return value can be ignored. FCODE is the BUILT_IN_*
@@ -3100,7 +3110,7 @@ gimple_fold_builtin_stxcpy_chk (gimple_stmt_iterator *gsi,
tree src, tree size,
enum built_in_function fcode)
{
- gimple *stmt = gsi_stmt (*gsi);
+ gcall *stmt = as_a <gcall *> (gsi_stmt (*gsi));
location_t loc = gimple_location (stmt);
bool ignore = gimple_call_lhs (stmt) == NULL_TREE;
tree len, fn;
@@ -3184,12 +3194,13 @@ gimple_fold_builtin_stxcpy_chk (gimple_stmt_iterator *gsi,
}
/* If __builtin_st{r,p}cpy_chk is used, assume st{r,p}cpy is available. */
- fn = builtin_decl_explicit (fcode == BUILT_IN_STPCPY_CHK
+ fn = builtin_decl_explicit (fcode == BUILT_IN_STPCPY_CHK && !ignore
? BUILT_IN_STPCPY : BUILT_IN_STRCPY);
if (!fn)
return false;
- gimple *repl = gimple_build_call (fn, 2, dest, src);
+ gcall *repl = gimple_build_call (fn, 2, dest, src);
+ dump_transformation (stmt, repl);
replace_call_with_call_and_fold (gsi, repl);
return true;
}
@@ -3205,23 +3216,10 @@ gimple_fold_builtin_stxncpy_chk (gimple_stmt_iterator *gsi,
tree len, tree size,
enum built_in_function fcode)
{
- gimple *stmt = gsi_stmt (*gsi);
+ gcall *stmt = as_a <gcall *> (gsi_stmt (*gsi));
bool ignore = gimple_call_lhs (stmt) == NULL_TREE;
tree fn;
- if (fcode == BUILT_IN_STPNCPY_CHK && ignore)
- {
- /* If return value of __stpncpy_chk is ignored,
- optimize into __strncpy_chk. */
- fn = builtin_decl_explicit (BUILT_IN_STRNCPY_CHK);
- if (fn)
- {
- gimple *repl = gimple_build_call (fn, 4, dest, src, len, size);
- replace_call_with_call_and_fold (gsi, repl);
- return true;
- }
- }
-
if (! tree_fits_uhwi_p (size))
return false;
@@ -3234,7 +3232,23 @@ gimple_fold_builtin_stxncpy_chk (gimple_stmt_iterator *gsi,
For MAXLEN only allow optimizing into non-_ocs function
if SIZE is >= MAXLEN, never convert to __ocs_fail (). */
if (maxlen == NULL_TREE || ! tree_fits_uhwi_p (maxlen))
- return false;
+ {
+ if (fcode == BUILT_IN_STPNCPY_CHK && ignore)
+ {
+ /* If return value of __stpncpy_chk is ignored,
+ optimize into __strncpy_chk. */
+ fn = builtin_decl_explicit (BUILT_IN_STRNCPY_CHK);
+ if (fn)
+ {
+ gimple *repl = gimple_build_call (fn, 4, dest, src, len,
+ size);
+ replace_call_with_call_and_fold (gsi, repl);
+ return true;
+ }
+ }
+
+ return false;
+ }
}
else
maxlen = len;
@@ -3244,12 +3258,13 @@ gimple_fold_builtin_stxncpy_chk (gimple_stmt_iterator *gsi,
}
/* If __builtin_st{r,p}ncpy_chk is used, assume st{r,p}ncpy is available. */
- fn = builtin_decl_explicit (fcode == BUILT_IN_STPNCPY_CHK
+ fn = builtin_decl_explicit (fcode == BUILT_IN_STPNCPY_CHK && !ignore
? BUILT_IN_STPNCPY : BUILT_IN_STRNCPY);
if (!fn)
return false;
- gimple *repl = gimple_build_call (fn, 3, dest, src, len);
+ gcall *repl = gimple_build_call (fn, 3, dest, src, len);
+ dump_transformation (stmt, repl);
replace_call_with_call_and_fold (gsi, repl);
return true;
}
diff --git a/gcc/testsuite/gcc.dg/fold-stringops-1.c b/gcc/testsuite/gcc.dg/fold-stringops-1.c
new file mode 100644
index 000000000000..e26632afd4e0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-stringops-1.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-lower-details" } */
+
+char dst[2048];
+
+char *
+copy1 (const char *src, int cond)
+{
+ __builtin___stpncpy_chk (dst, src, 42, __builtin_object_size (dst, 0));
+
+ return dst;
+}
+
+char *
+copy2 (void)
+{
+ __builtin___stpcpy_chk (dst, "Hello world", __builtin_object_size (dst, 0));
+
+ return dst;
+}
+/* { dg-final { scan-tree-dump "simplified __builtin___stpncpy_chk to __builtin_strncpy" "lower" } } */
+/* { dg-final { scan-tree-dump "simplified __builtin___stpcpy_chk to __builtin_strcpy" "lower" } } */
+
--
GitLab