Hi!
On the following testcase, we've regressed in bar since 8.x, in 8.x
store merging came up with mem = 64-bit constant, but starting with the
change to transform {0,1,2,3,4,5,6,7} char initializers into STRING_CSTs,
we don't do that anymore. The mem = STRING_CST expansion can do that,
but only if there are no embedded zeros. The following patch improves
it even for embedded zeros, by using a new callback for the
can_store_by_pieces/store_by_pieces calls which knows how to handle
STRING_CST. We don't need strlen in that case, can use TREE_STRING_CST
instead. Additionally, if the STRING_CST is slightly shorter than the
destination region, it might generate better code by trying to
store_by_pieces it all in one go (bytes from STRING_CST until the last one,
followed by artificially added zeros) and only if that doesn't seem to be
beneficial (e.g. very small STRING_CST followed by kilobytes of zeros)
goes for the store_by_pieces of STRING_CST (rounded up to next
STORE_MAX_PIECES) followed by a clear_storage.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2019-02-16 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/66152
* builtins.h (c_readstr): Declare.
* builtins.c (c_readstr): Remove forward declaration. Add
null_terminated_p argument, if false, read all bytes from the
string instead of stopping after '\0'.
* expr.c (string_cst_read_str): New function.
(store_expr): Use string_cst_read_str instead of
builtin_strncpy_read_str. Try to store by pieces the whole
exp_len first, and only if that fails, split it up into
store by pieces followed by clear_storage. Formatting fix.
* gcc.target/i386/pr66152.c: New test.
--- gcc/builtins.h.jj 2019-02-14 08:06:37.878546571 +0100
+++ gcc/builtins.h 2019-02-15 11:33:50.208180171 +0100
@@ -103,6 +103,7 @@ struct c_strlen_data
};
extern tree c_strlen (tree, int, c_strlen_data * = NULL, unsigned = 1);
+extern rtx c_readstr (const char *, scalar_int_mode, bool = true);
extern void expand_builtin_setjmp_setup (rtx, rtx);
extern void expand_builtin_setjmp_receiver (rtx);
extern void expand_builtin_update_setjmp_buf (rtx);
--- gcc/builtins.c.jj 2019-02-11 20:58:48.509965578 +0100
+++ gcc/builtins.c 2019-02-15 11:37:00.046029652 +0100
@@ -95,7 +95,6 @@ builtin_info_type builtin_info[(int)END_
/* Non-zero if __builtin_constant_p should be folded right away. */
bool force_folding_builtin_constant_p;
-static rtx c_readstr (const char *, scalar_int_mode);
static int target_char_cast (tree, char *);
static rtx get_memory_rtx (tree, tree);
static int apply_args_size (void);
@@ -802,10 +801,14 @@ c_strlen (tree src, int only_value, c_st
}
/* Return a constant integer corresponding to target reading
- GET_MODE_BITSIZE (MODE) bits from string constant STR. */
-
-static rtx
-c_readstr (const char *str, scalar_int_mode mode)
+ GET_MODE_BITSIZE (MODE) bits from string constant STR. If
+ NULL_TERMINATED_P, reading stops after '\0' character, all further ones
+ are assumed to be zero, otherwise it reads as many characters
+ as needed. */
+
+rtx
+c_readstr (const char *str, scalar_int_mode mode,
+ bool null_terminated_p/*=true*/)
{
HOST_WIDE_INT ch;
unsigned int i, j;
@@ -830,7 +833,7 @@ c_readstr (const char *str, scalar_int_m
j = j + UNITS_PER_WORD - 2 * (j % UNITS_PER_WORD) - 1;
j *= BITS_PER_UNIT;
- if (ch)
+ if (ch || !null_terminated_p)
ch = (unsigned char) str[i];
tmp[j / HOST_BITS_PER_WIDE_INT] |= ch << (j % HOST_BITS_PER_WIDE_INT);
}
--- gcc/expr.c.jj 2019-02-08 20:00:40.309835608 +0100
+++ gcc/expr.c 2019-02-15 11:37:18.715719809 +0100
@@ -5453,6 +5453,30 @@ emit_storent_insn (rtx to, rtx from)
return maybe_expand_insn (code, 2, ops);
}
+/* Helper function for store_expr storing of STRING_CST. */
+
+static rtx
+string_cst_read_str (void *data, HOST_WIDE_INT offset, scalar_int_mode mode)
+{
+ tree str = (tree) data;
+
+ gcc_assert (offset >= 0);
+ if (offset >= TREE_STRING_LENGTH (str))
+ return const0_rtx;
+
+ if ((unsigned HOST_WIDE_INT) offset + GET_MODE_SIZE (mode)
+ > (unsigned HOST_WIDE_INT) TREE_STRING_LENGTH (str))
+ {
+ char *p = XALLOCAVEC (char, GET_MODE_SIZE (mode));
+ size_t l = TREE_STRING_LENGTH (str) - offset;
+ memcpy (p, TREE_STRING_POINTER (str) + offset, l);
+ memset (p + l, '\0', GET_MODE_SIZE (mode) - l);
+ return c_readstr (p, mode, false);
+ }
+
+ return c_readstr (TREE_STRING_POINTER (str) + offset, mode, false);
+}
+
/* Generate code for computing expression EXP,
and storing the value into TARGET.
@@ -5472,7 +5496,7 @@ emit_storent_insn (rtx to, rtx from)
rtx
store_expr (tree exp, rtx target, int call_param_p,
- bool nontemporal, bool reverse)
+ bool nontemporal, bool reverse)
{
rtx temp;
rtx alt_rtl = NULL_RTX;
@@ -5606,36 +5630,32 @@ store_expr (tree exp, rtx target, int ca
if (TREE_STRING_LENGTH (str) <= 0)
goto normal_expr;
- str_copy_len = strlen (TREE_STRING_POINTER (str));
- if (str_copy_len < TREE_STRING_LENGTH (str) - 1)
- goto normal_expr;
+ if (can_store_by_pieces (exp_len, string_cst_read_str, (void *) str,
+ MEM_ALIGN (target), false))
+ {
+ store_by_pieces (target, exp_len, string_cst_read_str, (void *) str,
+ MEM_ALIGN (target), false, RETURN_BEGIN);
+ return NULL_RTX;
+ }
str_copy_len = TREE_STRING_LENGTH (str);
- if ((STORE_MAX_PIECES & (STORE_MAX_PIECES - 1)) == 0
- && TREE_STRING_POINTER (str)[TREE_STRING_LENGTH (str) - 1] == '\0')
+ if ((STORE_MAX_PIECES & (STORE_MAX_PIECES - 1)) == 0)
{
str_copy_len += STORE_MAX_PIECES - 1;
str_copy_len &= ~(STORE_MAX_PIECES - 1);
}
- str_copy_len = MIN (str_copy_len, exp_len);
- if (!can_store_by_pieces (str_copy_len, builtin_strncpy_read_str,
- CONST_CAST (char *, TREE_STRING_POINTER (str)),
- MEM_ALIGN (target), false))
+ if (str_copy_len >= exp_len)
goto normal_expr;
- dest_mem = target;
+ if (!can_store_by_pieces (str_copy_len, string_cst_read_str,
+ (void *) str, MEM_ALIGN (target), false))
+ goto normal_expr;
- memop_ret retmode = exp_len > str_copy_len ? RETURN_END : RETURN_BEGIN;
- dest_mem = store_by_pieces (dest_mem,
- str_copy_len, builtin_strncpy_read_str,
- CONST_CAST (char *,
- TREE_STRING_POINTER (str)),
- MEM_ALIGN (target), false,
- retmode);
- if (exp_len > str_copy_len)
- clear_storage (adjust_address (dest_mem, BLKmode, 0),
- GEN_INT (exp_len - str_copy_len),
- BLOCK_OP_NORMAL);
+ dest_mem = store_by_pieces (target, str_copy_len, string_cst_read_str,
+ (void *) str, MEM_ALIGN (target), false,
+ RETURN_END);
+ clear_storage (adjust_address (dest_mem, BLKmode, 0),
+ GEN_INT (exp_len - str_copy_len), BLOCK_OP_NORMAL);
return NULL_RTX;
}
else
--- gcc/testsuite/gcc.target/i386/pr66152.c.jj 2019-02-15 11:55:56.212164557
+0100
+++ gcc/testsuite/gcc.target/i386/pr66152.c 2019-02-15 11:56:47.769308378
+0100
@@ -0,0 +1,25 @@
+/* PR rtl-optimization/66152 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler "movabs\[^\n\r]*506097522914230528" { target {
! ia32 } } } } */
+/* { dg-final { scan-assembler "movabs\[^\n\r]*505813836079825408" { target {
! ia32 } } } } */
+/* { dg-final { scan-assembler "mov\[^\n\r]*50462976" { target ia32 } } } */
+/* { dg-final { scan-assembler "mov\[^\n\r]*117835012" { target ia32 } } } */
+/* { dg-final { scan-assembler "mov\[^\n\r]*100925952" { target ia32 } } } */
+/* { dg-final { scan-assembler "mov\[^\n\r]*117768961" { target ia32 } } } */
+
+void foo (char *);
+
+void
+bar (void)
+{
+ char a[] = {0,1,2,3,4,5,6,7};
+ foo (a);
+}
+
+void
+baz (void)
+{
+ char a[8] = "\0\2\4\6\1\3\5\7";
+ foo (a);
+}
Jakub
