This patch simplifies the alignment calculations in pad_below.
The first arm of the "if" was:
- taking GET_MODE_BITSIZE (always equal to GET_MODE_SIZE * BITS_PER_UNIT),
- rounding up to the next multiple of PARM_BOUNDARY
- converting bits to bytes and
- subtracting the GET_MODE_SIZE
so was in effect calculating the number of bytes needed to round
GET_MODE_SIZE up to (PARM_BOUNDARY / BITS_PER_UNIT). That can be
done more directly as -size & (align - 1), which is easier to
convert to variable-sized modes.
Tested on aarch64-linux-gnu and x86_64-linux-gnu, and by building
one target per CPU and checking that there were no differences in
assembly for the testsuite. OK to install?
Richard
2017-08-21 Richard Sandiford <richard.sandif...@linaro.org>
Alan Hayward <alan.hayw...@arm.com>
David Sherwood <david.sherw...@arm.com>
gcc/
* function.c (pad_below): Simplify padding calculation.
Index: gcc/function.c
===================================================================
--- gcc/function.c 2017-08-21 10:42:34.185530464 +0100
+++ gcc/function.c 2017-08-21 11:55:41.018148268 +0100
@@ -4322,21 +4322,16 @@ pad_to_arg_alignment (struct args_size *
static void
pad_below (struct args_size *offset_ptr, machine_mode passed_mode, tree
sizetree)
{
+ unsigned int align = PARM_BOUNDARY / BITS_PER_UNIT;
if (passed_mode != BLKmode)
- {
- if (GET_MODE_BITSIZE (passed_mode) % PARM_BOUNDARY)
- offset_ptr->constant
- += (((GET_MODE_BITSIZE (passed_mode) + PARM_BOUNDARY - 1)
- / PARM_BOUNDARY * PARM_BOUNDARY / BITS_PER_UNIT)
- - GET_MODE_SIZE (passed_mode));
- }
+ offset_ptr->constant += -GET_MODE_SIZE (passed_mode) & (align - 1);
else
{
if (TREE_CODE (sizetree) != INTEGER_CST
- || (TREE_INT_CST_LOW (sizetree) * BITS_PER_UNIT) % PARM_BOUNDARY)
+ || (TREE_INT_CST_LOW (sizetree) & (align - 1)) != 0)
{
/* Round the size up to multiple of PARM_BOUNDARY bits. */
- tree s2 = round_up (sizetree, PARM_BOUNDARY / BITS_PER_UNIT);
+ tree s2 = round_up (sizetree, align);
/* Add it in. */
ADD_PARM_SIZE (*offset_ptr, s2);
SUB_PARM_SIZE (*offset_ptr, sizetree);
