PING: [PATCH] PR target/67215: -fno-plt needs improvements for x86
H.J. Lu
hjl.tools@gmail.com
Mon Oct 19 19:59:00 GMT 2015
---------- Forwarded message ----------
From: H.J. Lu <hongjiu.lu@intel.com>
Date: Wed, Sep 9, 2015 at 3:02 PM
Subject: [PATCH] PR target/67215: -fno-plt needs improvements for x86
To: gcc-patches@gcc.gnu.org
prepare_call_address in calls.c is the wrong place to handle -fno-plt.
We shoudn't force function address into register and hope that load
function address via GOT and indirect call via register will be folded
into indirect call via GOT, which doesn't always happen. Also non-PIC
case can only be handled in backend. Instead, backend should expand
external function call into indirect call via GOT for -fno-plt.
This patch reverts -fno-plt in prepare_call_address and handles it in
ix86_expand_call. Other backends may need similar changes to support
-fno-plt. Alternately, we can introduce a target hook to indicate
whether an external function should be called via register for -fno-plt
so that i386 backend can disable it in prepare_call_address.
gcc/
PR target/67215
* calls.c (prepare_call_address): Don't handle -fno-plt here.
* config/i386/i386.c (ix86_expand_call): Generate indirect call
via GOT for -fno-plt. Support indirect call via GOT for x32.
* config/i386/predicates.md (sibcall_memory_operand): Allow
GOT memory operand.
gcc/testsuite/
PR target/67215
* gcc.target/i386/pr67215-1.c: New test.
* gcc.target/i386/pr67215-2.c: Likewise.
* gcc.target/i386/pr67215-3.c: Likewise.
---
gcc/calls.c | 12 ------
gcc/config/i386/i386.c | 71 ++++++++++++++++++++++++-------
gcc/config/i386/predicates.md | 7 ++-
gcc/testsuite/gcc.target/i386/pr67215-1.c | 20 +++++++++
gcc/testsuite/gcc.target/i386/pr67215-2.c | 20 +++++++++
gcc/testsuite/gcc.target/i386/pr67215-3.c | 13 ++++++
6 files changed, 114 insertions(+), 29 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/i386/pr67215-1.c
create mode 100644 gcc/testsuite/gcc.target/i386/pr67215-2.c
create mode 100644 gcc/testsuite/gcc.target/i386/pr67215-3.c
diff --git a/gcc/calls.c b/gcc/calls.c
index 026cb53..22c65cd 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -203,18 +203,6 @@ prepare_call_address (tree fndecl_or_type, rtx
funexp, rtx static_chain_value,
&& targetm.small_register_classes_for_mode_p (FUNCTION_MODE))
? force_not_mem (memory_address (FUNCTION_MODE, funexp))
: memory_address (FUNCTION_MODE, funexp));
- else if (flag_pic
- && fndecl_or_type
- && TREE_CODE (fndecl_or_type) == FUNCTION_DECL
- && (!flag_plt
- || lookup_attribute ("noplt", DECL_ATTRIBUTES (fndecl_or_type)))
- && !targetm.binds_local_p (fndecl_or_type))
- {
- /* This is done only for PIC code. There is no easy interface
to force the
- function address into GOT for non-PIC case. non-PIC case needs to be
- handled specially by the backend. */
- funexp = force_reg (Pmode, funexp);
- }
else if (! sibcallp)
{
if (!NO_FUNCTION_CSE && optimize && ! flag_no_function_cse)
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index d78f4e7..b9299d4 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -25649,21 +25649,54 @@ ix86_expand_call (rtx retval, rtx fnaddr,
rtx callarg1,
/* Static functions and indirect calls don't need the pic
register. Also,
check if PLT was explicitly avoided via no-plt or "noplt"
attribute, making
it an indirect call. */
+ rtx addr = XEXP (fnaddr, 0);
if (flag_pic
- && (!TARGET_64BIT
- || (ix86_cmodel == CM_LARGE_PIC
- && DEFAULT_ABI != MS_ABI))
- && GET_CODE (XEXP (fnaddr, 0)) == SYMBOL_REF
- && !SYMBOL_REF_LOCAL_P (XEXP (fnaddr, 0))
- && flag_plt
- && (SYMBOL_REF_DECL ((XEXP (fnaddr, 0))) == NULL_TREE
- || !lookup_attribute ("noplt",
- DECL_ATTRIBUTES (SYMBOL_REF_DECL (XEXP (fnaddr, 0))))))
+ && GET_CODE (addr) == SYMBOL_REF
+ && !SYMBOL_REF_LOCAL_P (addr))
{
- use_reg (&use, gen_rtx_REG (Pmode, REAL_PIC_OFFSET_TABLE_REGNUM));
- if (ix86_use_pseudo_pic_reg ())
- emit_move_insn (gen_rtx_REG (Pmode, REAL_PIC_OFFSET_TABLE_REGNUM),
- pic_offset_table_rtx);
+ if (flag_plt
+ && (SYMBOL_REF_DECL (addr) == NULL_TREE
+ || !lookup_attribute ("noplt",
+ DECL_ATTRIBUTES
(SYMBOL_REF_DECL (addr)))))
+ {
+ if (!TARGET_64BIT
+ || (ix86_cmodel == CM_LARGE_PIC
+ && DEFAULT_ABI != MS_ABI))
+ {
+ use_reg (&use, gen_rtx_REG (Pmode,
+ REAL_PIC_OFFSET_TABLE_REGNUM));
+ if (ix86_use_pseudo_pic_reg ())
+ emit_move_insn (gen_rtx_REG (Pmode,
+ REAL_PIC_OFFSET_TABLE_REGNUM),
+ pic_offset_table_rtx);
+ }
+ }
+ else if (!TARGET_PECOFF && !TARGET_MACHO)
+ {
+ if (TARGET_64BIT)
+ {
+ fnaddr = gen_rtx_UNSPEC (Pmode,
+ gen_rtvec (1, addr),
+ UNSPEC_GOTPCREL);
+ fnaddr = gen_rtx_CONST (Pmode, fnaddr);
+ }
+ else
+ {
+ fnaddr = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, addr),
+ UNSPEC_GOT);
+ fnaddr = gen_rtx_CONST (Pmode, fnaddr);
+ fnaddr = gen_rtx_PLUS (Pmode, pic_offset_table_rtx,
+ fnaddr);
+ }
+ fnaddr = gen_const_mem (Pmode, fnaddr);
+ /* Pmode may not be the same as word_mode for x32, which
+ doesn't support indirect branch via 32-bit memory slot.
+ Since x32 GOT slot is 64 bit with zero upper 32 bits,
+ indirect branch via x32 GOT slot is OK. */
+ if (GET_MODE (fnaddr) != word_mode)
+ fnaddr = gen_rtx_ZERO_EXTEND (word_mode, fnaddr);
+ fnaddr = gen_rtx_MEM (QImode, fnaddr);
+ }
}
}
@@ -25685,9 +25718,15 @@ ix86_expand_call (rtx retval, rtx fnaddr, rtx callarg1,
&& GET_CODE (XEXP (fnaddr, 0)) == SYMBOL_REF
&& !local_symbolic_operand (XEXP (fnaddr, 0), VOIDmode))
fnaddr = gen_rtx_MEM (QImode, construct_plt_address (XEXP (fnaddr, 0)));
- else if (sibcall
- ? !sibcall_insn_operand (XEXP (fnaddr, 0), word_mode)
- : !call_insn_operand (XEXP (fnaddr, 0), word_mode))
+ /* Since x32 GOT slot is 64 bit with zero upper 32 bits, indirect
+ branch via x32 GOT slot is OK. */
+ else if (!(TARGET_X32
+ && MEM_P (fnaddr)
+ && GET_CODE (XEXP (fnaddr, 0)) == ZERO_EXTEND
+ && GOT_memory_operand (XEXP (XEXP (fnaddr, 0), 0), Pmode))
+ && (sibcall
+ ? !sibcall_insn_operand (XEXP (fnaddr, 0), word_mode)
+ : !call_insn_operand (XEXP (fnaddr, 0), word_mode)))
{
fnaddr = convert_to_mode (word_mode, XEXP (fnaddr, 0), 1);
fnaddr = gen_rtx_MEM (QImode, copy_to_mode_reg (word_mode, fnaddr));
diff --git a/gcc/config/i386/predicates.md b/gcc/config/i386/predicates.md
index bc76a5b..822d834 100644
--- a/gcc/config/i386/predicates.md
+++ b/gcc/config/i386/predicates.md
@@ -593,7 +593,12 @@
;; Return true if OP is a memory operands that can be used in sibcalls.
(define_predicate "sibcall_memory_operand"
(and (match_operand 0 "memory_operand")
- (match_test "CONSTANT_P (XEXP (op, 0))")))
+ (match_test "CONSTANT_P (XEXP (op, 0))
+ || (GET_CODE (XEXP (op, 0)) == PLUS
+ && REG_P (XEXP (XEXP (op, 0), 0))
+ && GET_CODE (XEXP (XEXP (op, 0), 1)) == CONST
+ && GET_CODE (XEXP (XEXP (XEXP (op, 0), 1), 0)) == UNSPEC
+ && XINT (XEXP (XEXP (XEXP (op, 0), 1), 0), 1)
== UNSPEC_GOT)")))
;; Test for a valid operand for a call instruction.
;; Allow constant call address operands in Pmode only.
diff --git a/gcc/testsuite/gcc.target/i386/pr67215-1.c
b/gcc/testsuite/gcc.target/i386/pr67215-1.c
new file mode 100644
index 0000000..fd37f8e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr67215-1.c
@@ -0,0 +1,20 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fpic -fno-plt" } */
+
+extern char* bar (int);
+extern char* arr[32];
+
+void
+foo (void)
+{
+ int i;
+
+ for (i = 0; i < 32; i++)
+ arr[i] = bar (128);
+}
+
+/* { dg-final { scan-assembler "call\[ \t\]*.bar@GOTPCREL" { target {
! ia32 } } } } */
+/* { dg-final { scan-assembler "call\[ \t\]*.bar@GOT\\(" { target ia32 } } } */
+/* { dg-final { scan-assembler-not "mov(l|q)\[ \t\]*.bar@GOTPCREL" {
target { ! ia32 } } } } */
+/* { dg-final { scan-assembler-not "movl\[ \t\]*.bar@GOT\\(" { target
ia32 } } } */
+/* { dg-final { scan-assembler-not "call\[ \t\]*.bar@PLT" } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr67215-2.c
b/gcc/testsuite/gcc.target/i386/pr67215-2.c
new file mode 100644
index 0000000..ebf2919
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr67215-2.c
@@ -0,0 +1,20 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fpic" } */
+
+extern char* bar (int) __attribute__ ((noplt));
+extern char* arr[32];
+
+void
+foo (void)
+{
+ int i;
+
+ for (i = 0; i < 32; i++)
+ arr[i] = bar (128);
+}
+
+/* { dg-final { scan-assembler "call\[ \t\]*.bar@GOTPCREL" { target {
! ia32 } } } } */
+/* { dg-final { scan-assembler "call\[ \t\]*.bar@GOT\\(" { target ia32 } } } */
+/* { dg-final { scan-assembler-not "mov(l|q)\[ \t\]*.bar@GOTPCREL" {
target { ! ia32 } } } } */
+/* { dg-final { scan-assembler-not "movl\[ \t\]*.bar@GOT\\(" { target
ia32 } } } */
+/* { dg-final { scan-assembler-not "call\[ \t\]*.bar@PLT" } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr67215-3.c
b/gcc/testsuite/gcc.target/i386/pr67215-3.c
new file mode 100644
index 0000000..eb6bb39
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr67215-3.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fpic -fno-plt -fdump-rtl-expand" } */
+
+extern int bar (void);
+
+int
+foo (void)
+{
+ return bar ();
+}
+
+/* { dg-final { scan-rtl-dump "\\(call \\(mem:QI \\(mem/u/c:"
"expand" { target { ! x32 } } } } */
+/* { dg-final { scan-rtl-dump "\\(call \\(mem:QI \\(zero_extend:DI
\\(mem/u/c:" "expand" { target x32 } } } */
--
2.4.3
--
H.J.
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