RISC-V: reduce mcount save space on RV32

For RV32 we can reduce the size of the ABI save+restore state by using
SZREG so that register stores are packed rather than on an 8 byte
boundary.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20221115200832.706370-3-jamie@jamieiles.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
index 9cf0904..613bd07 100644 (file)
--- a/arch/riscv/kernel/mcount.S
+++ b/arch/riscv/kernel/mcount.S
@@ -15,8 +15,8 @@
 
        .macro SAVE_ABI_STATE
        addi    sp, sp, -16
-       REG_S   s0, 0(sp)
-       REG_S   ra, 8(sp)
+       REG_S   s0, 0*SZREG(sp)
+       REG_S   ra, 1*SZREG(sp)
        addi    s0, sp, 16
        .endm
 
@@ -25,24 +25,24 @@
         * register if a0 was not saved.
         */
        .macro SAVE_RET_ABI_STATE
-       addi    sp, sp, -32
-       REG_S   s0, 16(sp)
-       REG_S   ra, 24(sp)
-       REG_S   a0, 8(sp)
-       addi    s0, sp, 32
+       addi    sp, sp, -4*SZREG
+       REG_S   s0, 2*SZREG(sp)
+       REG_S   ra, 3*SZREG(sp)
+       REG_S   a0, 1*SZREG(sp)
+       addi    s0, sp, 4*SZREG
        .endm
 
        .macro RESTORE_ABI_STATE
-       REG_L   ra, 8(sp)
-       REG_L   s0, 0(sp)
+       REG_L   ra, 1*SZREG(sp)
+       REG_L   s0, 0*SZREG(sp)
        addi    sp, sp, 16
        .endm
 
        .macro RESTORE_RET_ABI_STATE
-       REG_L   ra, 24(sp)
-       REG_L   s0, 16(sp)
-       REG_L   a0, 8(sp)
-       addi    sp, sp, 32
+       REG_L   ra, 3*SZREG(sp)
+       REG_L   s0, 2*SZREG(sp)
+       REG_L   a0, 1*SZREG(sp)
+       addi    sp, sp, 4*SZREG
        .endm
 
 ENTRY(ftrace_stub)
@@ -101,10 +101,10 @@ ENTRY(MCOUNT_NAME)
  * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller)
  */
 do_ftrace_graph_caller:
-       addi    a0, s0, -8
+       addi    a0, s0, -SZREG
        mv      a1, ra
 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
-       REG_L   a2, -16(s0)
+       REG_L   a2, -2*SZREG(s0)
 #endif
        SAVE_ABI_STATE
        call    prepare_ftrace_return
@@ -117,7 +117,7 @@ do_ftrace_graph_caller:
  * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller)
  */
 do_trace:
-       REG_L   a1, -8(s0)
+       REG_L   a1, -SZREG(s0)
        mv      a0, ra
 
        SAVE_ABI_STATE