From 043d65862ab08441561a1fbc4cec23d4df1c18f2 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Tue, 9 Mar 2021 13:16:27 -0500 Subject: [PATCH] tcg/aarch64: Fix constant subtraction in tcg_out_addsub2 An hppa guest executing 0x000000000000e05c: ldil L%10000,r4 0x000000000000e060: ldo 0(r4),r4 0x000000000000e064: sub r3,r4,sp produces ---- 000000000000e064 000000000000e068 sub2_i32 tmp0,tmp4,r3,$0x1,$0x10000,$0x0 after folding and constant propagation. Then we hit tcg-target.c.inc:640: tcg_out_insn_3401: Assertion `aimm <= 0xfff' failed. because aimm is in fact -16, but unsigned. The ((bl < 0) ^ sub) condition which negates bl is incorrect and will always lead to this abort. If the constant is positive, sub will make it negative; if the constant is negative, sub will keep it negative. Backports 707b45a2475e25709f0dee00f8fdf39d346ed21e --- qemu/tcg/aarch64/tcg-target.inc.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/qemu/tcg/aarch64/tcg-target.inc.c b/qemu/tcg/aarch64/tcg-target.inc.c index e78203e4..5d8311ed 100644 --- a/qemu/tcg/aarch64/tcg-target.inc.c +++ b/qemu/tcg/aarch64/tcg-target.inc.c @@ -1402,10 +1402,10 @@ static void tcg_out_addsubi(TCGContext *s, int ext, TCGReg rd, } } -static inline void tcg_out_addsub2(TCGContext *s, TCGType ext, TCGReg rl, - TCGReg rh, TCGReg al, TCGReg ah, - tcg_target_long bl, tcg_target_long bh, - bool const_bl, bool const_bh, bool sub) +static void tcg_out_addsub2(TCGContext *s, TCGType ext, TCGReg rl, + TCGReg rh, TCGReg al, TCGReg ah, + tcg_target_long bl, tcg_target_long bh, + bool const_bl, bool const_bh, bool sub) { TCGReg orig_rl = rl; AArch64Insn insn; @@ -1415,11 +1415,13 @@ static inline void tcg_out_addsub2(TCGContext *s, TCGType ext, TCGReg rl, } if (const_bl) { - insn = I3401_ADDSI; - if ((bl < 0) ^ sub) { - insn = I3401_SUBSI; + if (bl < 0) { bl = -bl; + insn = sub ? I3401_ADDSI : I3401_SUBSI; + } else { + insn = sub ? I3401_SUBSI : I3401_ADDSI; } + if (unlikely(al == TCG_REG_XZR)) { /* ??? We want to allow al to be zero for the benefit of negation via subtraction. However, that leaves open the