On Tue, Feb 27, 2018 at 11:39 AM, H.J. Lu <hongjiu...@intel.com> wrote: > For x86 targets, when -fno-plt is used, external functions are called > via GOT slot, in 64-bit mode: > > [bnd] call/jmp *foo@GOTPCREL(%rip) > > and in 32-bit mode: > > [bnd] call/jmp *foo@GOT[(%reg)] > > With -mindirect-branch=, they are converted to, in 64-bit mode: > > pushq foo@GOTPCREL(%rip) > [bnd] jmp __x86_indirect_thunk[_bnd] > > and in 32-bit mode: > > pushl foo@GOT[(%reg)] > [bnd] jmp __x86_indirect_thunk[_bnd] > > which were incompatible with CFI. In 64-bit mode, since R11 is a scratch > register, we generate: > > movq foo@GOTPCREL(%rip), %r11 > [bnd] call/jmp __x86_indirect_thunk_[bnd_]r11 > > instead. We do it in ix86_output_indirect_branch so that we can use > the newly proposed R_X86_64_THUNK_GOTPCRELX relocation: > > https://groups.google.com/forum/#!topic/x86-64-abi/eED5lzn3_Mg > > movq foo@OTPCREL_THUNK(%rip), %r11 > [bnd] call/jmp __x86_indirect_thunk_[bnd_]r11 > > to load GOT slot into R11. If foo is defined locally, linker can can > convert > > movq foo@GOTPCREL_THUNK(%rip), %reg > call/jmp __x86_indirect_thunk_reg > > to > > call/jmp foo > nop 0L(%rax) > > In 32-bit mode, since all caller-saved registers, EAX, EDX and ECX, may > used to function parameters, there is no scratch register available. For > -fno-plt -fno-pic -mindirect-branch=, we expand external function call > to: > > movl foo@GOT, %reg > [bnd] call/jmp *%reg > > so that it can be converted to > > movl foo@GOT, %reg > [bnd] call/jmp __x86_indirect_thunk_[bnd_]reg > > in ix86_output_indirect_branch. Since this is performed during RTL > expansion, other instructions may be inserted between movl and call/jmp. > Linker optimization isn't always possible. > > Tested on i686 and x86-64. OK for trunk? > > > H.J. > --- > gcc/ > > PR target/83970 > * config/i386/constraints.md (Bs): Allow GOT_memory_operand > for TARGET_LP64 with indirect branch conversion. > (Bw): Likewise. > * config/i386/i386.c (ix86_expand_call): Handle -fno-plt with > -mindirect-branch=. > (ix86_nopic_noplt_attribute_p): Likewise. > (ix86_output_indirect_branch): In 64-bit mode, convert function > call via GOT with R11 as a scratch register using > __x86_indirect_thunk_r11. > (ix86_output_call_insn): In 64-bit mode, set xasm to NULL when > calling ix86_output_indirect_branch with function call via GOT. > * config/i386/i386.md (*call_got_thunk): New call pattern for > TARGET_LP64 with indirect branch conversion. > (*call_value_got_thunk): Likewise. > > gcc/testsuite/ > > PR target/83970 > * gcc.target/i386/indirect-thunk-5.c: Updated. > * gcc.target/i386/indirect-thunk-6.c: Likewise. > * gcc.target/i386/indirect-thunk-bnd-3.c: Likewise. > * gcc.target/i386/indirect-thunk-bnd-4.c: Likewise. > * gcc.target/i386/indirect-thunk-extern-5.c: Likewise. > * gcc.target/i386/indirect-thunk-extern-6.c: Likewise. > * gcc.target/i386/indirect-thunk-inline-5.c: Likewise. > * gcc.target/i386/indirect-thunk-inline-6.c: Likewise. > * gcc.target/i386/indirect-thunk-13.c: New test. > * gcc.target/i386/indirect-thunk-14.c: Likewise. > * gcc.target/i386/indirect-thunk-bnd-5.c: Likewise. > * gcc.target/i386/indirect-thunk-bnd-6.c: Likewise. > * gcc.target/i386/indirect-thunk-extern-11.c: Likewise. > * gcc.target/i386/indirect-thunk-extern-12.c: Likewise. > * gcc.target/i386/indirect-thunk-inline-8.c: Likewise. > * gcc.target/i386/indirect-thunk-inline-9.c: Likewise.
PING: https://gcc.gnu.org/ml/gcc-patches/2018-02/msg01527.html -- H.J.