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target/arm: Make FEAT_MOPS SET* insns handle Xs == XZR correctly

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Most of the registers used by the FEAT_MOPS instructions cannot use
31 as a register field value; this is CONSTRAINED UNPREDICTABLE to
NOP or UNDEF (we UNDEF).  However, it is permitted for the "source
value" register for the memset insns SET* to be 31, which (as usual
for most data-processing insns) means it should be the zero register
XZR. We forgot to handle this case, with the effect that trying to
set memory to zero with a "SET* Xd, Xn, XZR" sets the memory to
the value that happens to be in the low byte of SP.

Handle XZR when getting the SET* data value from the register file.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20231030174000.3792225-4-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2023-10-30 17:40:00 +00:00
parent 63c1b7de0a
commit 854c001f12
1 changed files with 12 additions and 3 deletions
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15
target/arm/tcg/helper-a64.c
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@ -1206,6 +1206,15 @@ static void check_setg_alignment(CPUARMState *env, uint64_t ptr, uint64_t size,
}
}
static uint64_t arm_reg_or_xzr(CPUARMState *env, int reg)
{
/*
* Runtime equivalent of cpu_reg() -- return the CPU register value,
* for contexts when index 31 means XZR (not SP).
*/
return reg == 31 ? 0 : env->xregs[reg];
}
/*
* For the Memory Set operation, our implementation chooses
* always to use "option A", where we update Xd to the final
@ -1226,7 +1235,7 @@ static void do_setp(CPUARMState *env, uint32_t syndrome, uint32_t mtedesc,
int rd = mops_destreg(syndrome);
int rs = mops_srcreg(syndrome);
int rn = mops_sizereg(syndrome);
uint8_t data = env->xregs[rs];
uint8_t data = arm_reg_or_xzr(env, rs);
uint32_t memidx = FIELD_EX32(mtedesc, MTEDESC, MIDX);
uint64_t toaddr = env->xregs[rd];
uint64_t setsize = env->xregs[rn];
@ -1286,7 +1295,7 @@ static void do_setm(CPUARMState *env, uint32_t syndrome, uint32_t mtedesc,
int rd = mops_destreg(syndrome);
int rs = mops_srcreg(syndrome);
int rn = mops_sizereg(syndrome);
uint8_t data = env->xregs[rs];
uint8_t data = arm_reg_or_xzr(env, rs);
uint64_t toaddr = env->xregs[rd] + env->xregs[rn];
uint64_t setsize = -env->xregs[rn];
uint32_t memidx = FIELD_EX32(mtedesc, MTEDESC, MIDX);
@ -1349,7 +1358,7 @@ static void do_sete(CPUARMState *env, uint32_t syndrome, uint32_t mtedesc,
int rd = mops_destreg(syndrome);
int rs = mops_srcreg(syndrome);
int rn = mops_sizereg(syndrome);
uint8_t data = env->xregs[rs];
uint8_t data = arm_reg_or_xzr(env, rs);
uint64_t toaddr = env->xregs[rd] + env->xregs[rn];
uint64_t setsize = -env->xregs[rn];
uint32_t memidx = FIELD_EX32(mtedesc, MTEDESC, MIDX);