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target/arm: Merge arm_cpu_vq_map_next_smaller into sole caller

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Coverity reports, in sve_zcr_get_valid_len,

"Subtract operation overflows on operands
arm_cpu_vq_map_next_smaller(cpu, start_vq + 1U) and 1U"

First, the aarch32 stub version of arm_cpu_vq_map_next_smaller,
returning 0, does exactly what Coverity reports.  Remove it.

Second, the aarch64 version of arm_cpu_vq_map_next_smaller has
a set of asserts, but they don't cover the case in question.
Further, there is a fair amount of extra arithmetic needed to
convert from the 0-based zcr register, to the 1-base vq form,
to the 0-based bitmap, and back again.  This can be simplified
by leaving the value in the 0-based form.

Finally, use test_bit to simplify the common case, where the
length in the zcr registers is in fact a supported length.

Reported-by: Coverity (CID 1407217)
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Message-id: 20191118091414.19440-1-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Richard Henderson 2019-11-19 13:20:27 +00:00 committed by Peter Maydell
parent 83ad95957c
commit 6e553f2a1b
3 changed files with 7 additions and 20 deletions
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3
target/arm/cpu.h
View file

@ -185,12 +185,9 @@ typedef struct {
#ifdef TARGET_AARCH64
# define ARM_MAX_VQ 16
void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp);
uint32_t arm_cpu_vq_map_next_smaller(ARMCPU *cpu, uint32_t vq);
#else
# define ARM_MAX_VQ 1
static inline void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp) { }
static inline uint32_t arm_cpu_vq_map_next_smaller(ARMCPU *cpu, uint32_t vq)
{ return 0; }
#endif
typedef struct ARMVectorReg {

15
target/arm/cpu64.c
View file

@ -458,21 +458,6 @@ void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp)
cpu->sve_max_vq = max_vq;
}
uint32_t arm_cpu_vq_map_next_smaller(ARMCPU *cpu, uint32_t vq)
{
uint32_t bitnum;
/*
* We allow vq == ARM_MAX_VQ + 1 to be input because the caller may want
* to find the maximum vq enabled, which may be ARM_MAX_VQ, but this
* function always returns the next smaller than the input.
*/
assert(vq && vq <= ARM_MAX_VQ + 1);
bitnum = find_last_bit(cpu->sve_vq_map, vq - 1);
return bitnum == vq - 1 ? 0 : bitnum + 1;
}
static void cpu_max_get_sve_max_vq(Object *obj, Visitor *v, const char *name,
void *opaque, Error **errp)
{

9
target/arm/helper.c
View file

@ -5363,9 +5363,14 @@ int sve_exception_el(CPUARMState *env, int el)
static uint32_t sve_zcr_get_valid_len(ARMCPU *cpu, uint32_t start_len)
{
uint32_t start_vq = (start_len & 0xf) + 1;
uint32_t end_len;
return arm_cpu_vq_map_next_smaller(cpu, start_vq + 1) - 1;
end_len = start_len &= 0xf;
if (!test_bit(start_len, cpu->sve_vq_map)) {
end_len = find_last_bit(cpu->sve_vq_map, start_len);
assert(end_len < start_len);
}
return end_len;
}
/*