The operation mix comprises these groups:
To trigger ASE_SPEC and ASE_INST_SPEC, create a function using NEON instructions:
.global simd
.type simd, "function"
.cfi_startproc
.global simd
simd:
LDR X0, =array
LD2 {v0.4S, v1.4S}, [x0]
ADD V2.4S, V0.4S, V1.4S
RET
.cfi_endproc
.data
array: .word 10, 20, 30, 40, 50, 60
The resulting event counts for this code are:
INST_SPEC is 12
ASE_SPEC is 1
ASE_INST_SPEC is 3
The results show ASE_SPEC is 1 and ASE_INST_SPEC is 3. ASE_INST_SPEC counts speculatively executed Advanced SIMD operations. Meanwhile, ASE_SPEC counts speculatively executed Advanced SIMD operations, excluding load, store, and move micro-operations that move data to or from the SIMD registers. ASE_INST_SPEC counts 1 from LD2 and 2 from ADD: adding, then storing. ASE_SPEC only counts 1 from the actual NEON add operation.
To trigger VFP_SPEC, a scalar adding function is made:
.global scalar_fp
.type scalar_fp, "function"
.cfi_startproc
.global scalar_fp
scalar_fp:
FMOV D1, #1.5
FMOV D2, #3.0
ADD D0, D1, D2
RET
.cfi_endproc
The resulting event counts for the code are:
INST_SPEC is 11
VFP_SPEC is 2
This happens because VFP_SPEC does not count instructions that move data to or from floating point registers, it only counts the ADD operation. The results show that VFP_SPEC is 2. Although there is one ADD operation, the floating point instruction can be split up into two micro-operations.
The following code uses a GCD function to trigger DP_SPEC, BR_IMMED_SPEC, and BR_INDIRECT_SPEC.
.section GCD,"ax"
.align 3
.global gcd
.type gcd, @function
.cfi_startproc
gcd:
CMP W0, W1
B.EQ exit
B.LT less
SUB W0, W0, W1
B gcd
less:
SUB W1, W1, W0
B gcd
exit:
RET
.cfi_endproc
void branch_test()
{
int ans, e, f;
e = 50;
f = 75;
for (int i = 0; i < 5; i++)
{
ans = gcd(e, f);
e+=5;
f+=5;
}
}
The resulting event counts for the code are:
INST_SPEC is 326
DP_SPEC is 136
BR_INDIRECT_SPEC is 6
BR_IMMED_SPEC is 113
DP_SPEC is triggered by speculatively executed logical or arithmetic instructions. BR_IMMED_SPEC is triggered by immediate branch instructions, including B <> and B.cond <>. Lastly, BR_INDIRECT_SPEC is triggered by any instructions that force a software change of the program counter that are speculatively executed, including RET.