From: "Roger Sayle" <roger@nextmovesoftware.com>
To: <gcc-patches@gcc.gnu.org>
Subject: [PATCH] PR middle-end/105853: Call store_constructor directly from calls.cc.
Date: Mon, 6 Jun 2022 14:50:11 +0100 [thread overview]
Message-ID: <001601d879ac$584d33e0$08e79ba0$@nextmovesoftware.com> (raw)
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This patch fixes both ICE regressions PR middle-end/105853 and
PR target/105856 caused by my recent patch to expand small const structs
as immediate constants. That patch updated code generation in three
places: two in expr.cc that call store_constructor directly, and the
third in calls.cc's load_register_parameters that expands its CONSTRUCTOR
via expand_expr, as store_constructor is local/static to expr.cc, and
the "public" API, should usually simply forward the constructor to the
appropriate store_constructor function.
Alas, despite the clean regression testing on multiple targets, the above
ICEs show that expand_expr isn't a suitable proxy for store_constructor,
and things that (I'd assumed) shouldn't affect how/whether a struct is
placed in a register [such as whether the struct is considered packed/
aligned or not] actually interfere with the optimization that is being
attempted.
The (proposed) solution is to export store_constructor (and it's helper
function int_expr_size) from expr.cc, by removing their static qualifier
and prototyping both functions in expr.h, so they can be called directly
from load_register_parameters in calls.cc. This cures both ICEs, but
almost as important produces much better code generation than GCC 12.
For PR 105853, GCC 12 generates:
compose_nd_na_ipv6_src:
movzx eax, WORD PTR eth_addr_zero[rip+2]
movzx edx, WORD PTR eth_addr_zero[rip]
movzx edi, WORD PTR eth_addr_zero[rip+4]
sal rax, 16
or rax, rdx
sal rdi, 32
or rdi, rax
xor eax, eax
jmp packet_set_nd
eth_addr_zero: .zero 6
where now (with this fix) GCC 13 generates:
compose_nd_na_ipv6_src:
xorl %edi, %edi
xorl %eax, %eax
jmp packet_set_nd
Likewise, for PR 105856 on ARM, we'd previously generate:
g_329_3:
movw r3, #:lower16:.LANCHOR0
movt r3, #:upper16:.LANCHOR0
ldr r0, [r3]
b func_19
but with this optimization we now generate:
g_329_3:
mov r0, #6
b func_19
This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check with no new failures. I've also confirmed that on a
cross-compiler to arm-linux-gnueabihf --with-arch=armv6 this fixes the
target specific ICE in PR105856. The make check is currently running
with --target_board=unix{-m32}, OK for mainline if that also passes?
My sincere apologies for the inconvenience.
2022-06-06 Roger Sayle <roger@nextmovesoftware.com>
gcc/ChangeLog
PR middle-end/105853
PR target/105856
* calls.cc (load_register_parameters): Call store_constructor
(and int_Expr_size) directly instead of expanding via expand_expr.
* expr.cc (static void store_constructor): Don't prototype here.
(static HOST_WIDE_INT int_expr_size): Likewise.
(store_constructor): No longer static.
(int_expr_size): Likewise, no longer static.
* expr.h (store_constructor): Prototype here.
(int_expr_size): Prototype here.
gcc/testsuite/ChangeLog
PR middle-end/105853
PR target/105856
* gcc.dg/pr105853.c: New test case.
* gcc.dg/pr105856.c: New test case.
Roger
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diff --git a/gcc/calls.cc b/gcc/calls.cc
index a4336c1..f4e1299 100644
--- a/gcc/calls.cc
+++ b/gcc/calls.cc
@@ -2186,10 +2186,11 @@ load_register_parameters (struct arg_data *args, int num_actuals,
&& immediate_const_ctor_p (DECL_INITIAL (tree_value)))
{
rtx target = gen_reg_rtx (word_mode);
- rtx x = expand_expr (DECL_INITIAL (tree_value),
- target, word_mode, EXPAND_NORMAL);
+ store_constructor (DECL_INITIAL (tree_value), target, 0,
+ int_expr_size (DECL_INITIAL (tree_value)),
+ false);
reg = gen_rtx_REG (word_mode, REGNO (reg));
- emit_move_insn (reg, x);
+ emit_move_insn (reg, target);
}
else if (partial == 0 || args[i].pass_on_stack)
{
diff --git a/gcc/expr.cc b/gcc/expr.cc
index fb062dc..85cb414 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -84,7 +84,6 @@ static void emit_block_move_via_loop (rtx, rtx, rtx, unsigned);
static void clear_by_pieces (rtx, unsigned HOST_WIDE_INT, unsigned int);
static rtx_insn *compress_float_constant (rtx, rtx);
static rtx get_subtarget (rtx);
-static void store_constructor (tree, rtx, int, poly_int64, bool);
static rtx store_field (rtx, poly_int64, poly_int64, poly_uint64, poly_uint64,
machine_mode, tree, alias_set_type, bool, bool);
@@ -100,7 +99,6 @@ static void do_tablejump (rtx, machine_mode, rtx, rtx, rtx,
profile_probability);
static rtx const_vector_from_tree (tree);
static tree tree_expr_size (const_tree);
-static HOST_WIDE_INT int_expr_size (const_tree);
static void convert_mode_scalar (rtx, rtx, int);
\f
@@ -6757,7 +6755,7 @@ fields_length (const_tree type)
which has been packed to exclude padding bits.
If REVERSE is true, the store is to be done in reverse order. */
-static void
+void
store_constructor (tree exp, rtx target, int cleared, poly_int64 size,
bool reverse)
{
@@ -13209,7 +13207,7 @@ expr_size (tree exp)
/* Return a wide integer for the size in bytes of the value of EXP, or -1
if the size can vary or is larger than an integer. */
-static HOST_WIDE_INT
+HOST_WIDE_INT
int_expr_size (const_tree exp)
{
tree size;
diff --git a/gcc/expr.h b/gcc/expr.h
index d777c28..0351183 100644
--- a/gcc/expr.h
+++ b/gcc/expr.h
@@ -339,6 +339,8 @@ extern bool categorize_ctor_elements (const_tree, HOST_WIDE_INT *,
HOST_WIDE_INT *, HOST_WIDE_INT *,
bool *);
extern bool immediate_const_ctor_p (const_tree, unsigned int words = 1);
+extern void store_constructor (tree, rtx, int, poly_int64, bool);
+extern HOST_WIDE_INT int_expr_size (const_tree exp);
extern void expand_operands (tree, tree, rtx, rtx*, rtx*,
enum expand_modifier);
diff --git a/gcc/testsuite/gcc.dg/pr105853.c b/gcc/testsuite/gcc.dg/pr105853.c
new file mode 100644
index 0000000..4f234ac
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr105853.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+struct {
+ struct {
+ short e16[3];
+ }
+} const eth_addr_zero = {{}}; /* { dg-warning "no semicolon at" } */
+void compose_nd_na_ipv6_src() {
+ packet_set_nd(eth_addr_zero); /* { dg-warning "implicit declaration" } */
+}
diff --git a/gcc/testsuite/gcc.dg/pr105856.c b/gcc/testsuite/gcc.dg/pr105856.c
new file mode 100644
index 0000000..dd3aa2f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr105856.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+#pragma pack(1)
+struct {
+ unsigned f0;
+} static g_251 = {6};
+void g_329_3() {
+ func_19(g_251); /* { dg-warning "implicit declaration" } */
+}
+
next reply other threads:[~2022-06-06 13:50 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-06 13:50 Roger Sayle [this message]
2022-06-07 8:04 ` Eric Botcazou
2022-06-12 17:16 ` Jeff Law
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