On Sun, Mar 11, 2018 at 7:40 AM, H.J. Lu <hjl.to...@gmail.com> wrote: > On Mon, Mar 5, 2018 at 4:20 AM, H.J. Lu <hjl.to...@gmail.com> wrote: >> 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 >> > > PING. >
PING. -- H.J.
