Use 'regs' as a contiguous linear bitmap for bitwise operations in
apic_{set|clear|test}_vector(). This makes the code simpler by eliminating
the need to determine the offset of the 32-bit register and the vector bit
location within that register prior to performing bitwise operations.
This change results in slight increase in generated code size for
gcc-14.2.
- Without change
apic_set_vector:
89 f8 mov %edi,%eax
83 e7 1f and $0x1f,%edi
c1 e8 05 shr $0x5,%eax
c1 e0 04 shl $0x4,%eax
48 01 c6 add %rax,%rsi
f0 48 0f ab 3e lock bts %rdi,(%rsi)
c3 ret
- With change
apic_set_vector:
89 f8 mov %edi,%eax
c1 e8 05 shr $0x5,%eax
8d 04 40 lea (%rax,%rax,2),%eax
c1 e0 05 shl $0x5,%eax
01 f8 add %edi,%eax
89 c0 mov %eax,%eax
f0 48 0f ab 3e lock bts %rax,(%rsi)
c3 ret
But, lapic.o text size (bytes) decreases with this change:
Obj Old-size New-size
lapic.o 28832 28768
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@xxxxxxx>
---
Changes since v7:
- Commit log update.
arch/x86/include/asm/apic.h | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index b7cbe9ba363e..f91d23757375 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -564,19 +564,28 @@ static __always_inline void apic_set_reg64(void *regs, int reg, u64 val)
ap->regs64[reg / 8] = val;
}
+static inline unsigned int get_vec_bit(unsigned int vec)
+{
+ /*
+ * The registers are 32-bit wide and 16-byte aligned.
+ * Compensate for the resulting bit number spacing.
+ */
+ return vec + 96 * (vec / 32);
+}
+
static inline void apic_clear_vector(int vec, void *bitmap)
{
- clear_bit(APIC_VECTOR_TO_BIT_NUMBER(vec), bitmap + APIC_VECTOR_TO_REG_OFFSET(vec));
+ clear_bit(get_vec_bit(vec), bitmap);
}
static inline void apic_set_vector(int vec, void *bitmap)
{
- set_bit(APIC_VECTOR_TO_BIT_NUMBER(vec), bitmap + APIC_VECTOR_TO_REG_OFFSET(vec));
+ set_bit(get_vec_bit(vec), bitmap);
}
static inline int apic_test_vector(int vec, void *bitmap)
{
- return test_bit(APIC_VECTOR_TO_BIT_NUMBER(vec), bitmap + APIC_VECTOR_TO_REG_OFFSET(vec));
+ return test_bit(get_vec_bit(vec), bitmap);
}
/*
--
2.34.1
