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commit 8ade1936895516ea40a89dc88daf4267df60b226 Author: H.J. Lu hjl.tools@gmail.com Date: Sun Aug 16 04:46:20 2015 -0700
Properly handle -fno-plt in ix86_expand_call
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 | 12 ++++++ 6 files changed, 113 insertions(+), 29 deletions(-)
diff --git a/gcc/calls.c b/gcc/calls.c index 5636725..7cce9be 100644 --- a/gcc/calls.c +++ b/gcc/calls.c @@ -203,18 +203,6 @@ prepare_call_address (tree fndecl_or_type, rtx funexp, rtx sta [...] && 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 05fa5e1..ac9a6c4 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 a9c8623..be2df76 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/i [...] 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 { ! ia [...] +/* { 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/i [...] 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 { ! ia [...] +/* { 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/i [...] new file mode 100644 index 0000000..dbd9a2f --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr67215-3.c @@ -0,0 +1,12 @@ +/* { 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" } } */