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target/arm: Avoid writing to constant TCGv in trans_CSEL()

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In commit 0b188ea05a we changed the implementation of
trans_CSEL() to use tcg_constant_i32(). However, this change
was incorrect, because the implementation of the function
sets up the TCGv_i32 rn and rm to be either zero or else
a TCG temp created in load_reg(), and these TCG temps are
then in both cases written to by the emitted TCG ops.
The result is that we hit a TCG assertion:

qemu-system-arm: ../../tcg/tcg.c:4455: tcg_reg_alloc_mov: Assertion `!temp_readonly(ots)' failed.

(or on a non-debug build, just produce a garbage result)

Adjust the code so that rn and rm are always writeable
temporaries whether the instruction is using the special
case "0" or a normal register as input.

Cc: qemu-stable@nongnu.org
Fixes: 0b188ea05a ("target/arm: Use tcg_constant in trans_CSEL")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230727103906.2641264-1-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2023-07-27 11:39:06 +01:00
parent 548b8edc6d
commit 2b0d656ab6
1 changed files with 8 additions and 7 deletions
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15
target/arm/tcg/translate.c
View file

@ -8799,7 +8799,7 @@ static bool trans_IT(DisasContext *s, arg_IT *a)
/* v8.1M CSEL/CSINC/CSNEG/CSINV */
static bool trans_CSEL(DisasContext *s, arg_CSEL *a)
{
TCGv_i32 rn, rm, zero;
TCGv_i32 rn, rm;
DisasCompare c;
if (!arm_dc_feature(s, ARM_FEATURE_V8_1M)) {
@ -8817,16 +8817,17 @@ static bool trans_CSEL(DisasContext *s, arg_CSEL *a)
}
/* In this insn input reg fields of 0b1111 mean "zero", not "PC" */
zero = tcg_constant_i32(0);
rn = tcg_temp_new_i32();
rm = tcg_temp_new_i32();
if (a->rn == 15) {
rn = zero;
tcg_gen_movi_i32(rn, 0);
} else {
rn = load_reg(s, a->rn);
load_reg_var(s, rn, a->rn);
}
if (a->rm == 15) {
rm = zero;
tcg_gen_movi_i32(rm, 0);
} else {
rm = load_reg(s, a->rm);
load_reg_var(s, rm, a->rm);
}
switch (a->op) {
@ -8846,7 +8847,7 @@ static bool trans_CSEL(DisasContext *s, arg_CSEL *a)
}
arm_test_cc(&c, a->fcond);
tcg_gen_movcond_i32(c.cond, rn, c.value, zero, rn, rm);
tcg_gen_movcond_i32(c.cond, rn, c.value, tcg_constant_i32(0), rn, rm);
store_reg(s, a->rd, rn);
return true;