> On May 6, 2022, at 10:58 AM, Uros Bizjak <ubiz...@gmail.com> wrote: > > On Fri, May 6, 2022 at 4:29 PM Qing Zhao <qing.z...@oracle.com> wrote: >> >> Hi, >> >> As Kee’s requested in this PR: >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101891 >> >> ===== >> >> Currently -fzero-call-used-regs will use a pattern of: >> >> XOR regA,regA >> MOV regA,regB >> MOV regA,regC >> ... >> RET >> >> However, this introduces both a register ordering dependency (e.g. the CPU >> cannot clear regB without clearing regA first), and while greatly reduces >> available ROP gadgets, it does technically leave a set of "MOV" ROP gadgets >> at the end of functions (e.g. "MOV regA,regC; RET"). >> >> Please switch to always using XOR: >> >> XOR regA,regA >> XOR regB,regB >> XOR regC,regC >> ... >> RET >> >> ======= >> >> This patch switch all MOV to XOR on i386. >> >> Bootstrapped and regresstion tested on x86_64-linux-gnu. >> >> Okay for gcc13? >> >> Thanks. >> >> Qing >> >> ========================================== > >> gcc/ChangeLog: >> >> * config/i386/i386.cc (zero_all_mm_registers): Use SET to zero instead >> of MOV for zeroing scratch registers. >> (ix86_zero_call_used_regs): Likewise. >> >> gcc/testsuite/ChangeLog: >> >> * gcc.target/i386/zero-scratch-regs-1.c: Add -fno-stack-protector >> -fno-PIC. >> * gcc.target/i386/zero-scratch-regs-10.c: Adjust mov to xor. >> * gcc.target/i386/zero-scratch-regs-13.c: Add -msse. >> * gcc.target/i386/zero-scratch-regs-14.c: Adjust mov to xor. >> * gcc.target/i386/zero-scratch-regs-15.c: Add -fno-stack-protector >> -fno-PIC. >> * gcc.target/i386/zero-scratch-regs-16.c: Likewise. >> * gcc.target/i386/zero-scratch-regs-17.c: Likewise. >> * gcc.target/i386/zero-scratch-regs-18.c: Add -fno-stack-protector >> -fno-PIC, adjust mov to xor. >> * gcc.target/i386/zero-scratch-regs-19.c: Add -fno-stack-protector >> -fno-PIC. >> * gcc.target/i386/zero-scratch-regs-2.c: Adjust mov to xor. >> * gcc.target/i386/zero-scratch-regs-20.c: Add -msse. >> * gcc.target/i386/zero-scratch-regs-21.c: Add -fno-stack-protector >> -fno-PIC, Adjust mov to xor. >> * gcc.target/i386/zero-scratch-regs-22.c: Adjust mov to xor. >> * gcc.target/i386/zero-scratch-regs-23.c: Likewise. >> * gcc.target/i386/zero-scratch-regs-26.c: Likewise. >> * gcc.target/i386/zero-scratch-regs-27.c: Likewise. >> * gcc.target/i386/zero-scratch-regs-28.c: Likewise. >> * gcc.target/i386/zero-scratch-regs-3.c: Add -fno-stack-protector. >> * gcc.target/i386/zero-scratch-regs-31.c: Adjust mov to xor. >> * gcc.target/i386/zero-scratch-regs-4.c: Add -fno-stack-protector >> -fno-PIC. >> * gcc.target/i386/zero-scratch-regs-5.c: Adjust mov to xor. >> * gcc.target/i386/zero-scratch-regs-6.c: Add -fno-stack-protector. >> * gcc.target/i386/zero-scratch-regs-7.c: Likewise. >> * gcc.target/i386/zero-scratch-regs-8.c: Adjust mov to xor. >> * gcc.target/i386/zero-scratch-regs-9.c: Add -fno-stack-protector. > > Please use something like the attached (functionally equivalent) patch > for the last hunk of your patch.
Sure, I will update the code. > > Also, if possible, please use V2SImode as a generic MMX mode instead > of V4HImode. What’s the major purpose of this change? thanks. Qing > > OK with the above changes. > > Thanks, > Uros. > <p.diff.txt>
