When auto-inc-dec creates a new mem to compute the cost of doing some
transform, it forgets to copy over the alignment of the original mem.
This gives wrong costs, for example, for rs6000 a floating point load
or store is hugely expensive if unaligned. This patch fixes it.
This doesn't fix any test case I'm aware of, but it is a very simple
patch. Is it okay for trunk?
Segher
2019-04-17 Segher Boessenkool <seg...@kernel.crashing.org>
* auto-inc-dec.c (attempt_change): Set the alignment of the
temporary memory to that of the original.
---
gcc/auto-inc-dec.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/gcc/auto-inc-dec.c b/gcc/auto-inc-dec.c
index 43400cc..bdb6efa 100644
--- a/gcc/auto-inc-dec.c
+++ b/gcc/auto-inc-dec.c
@@ -471,6 +471,7 @@ attempt_change (rtx new_addr, rtx inc_reg)
int regno;
rtx mem = *mem_insn.mem_loc;
machine_mode mode = GET_MODE (mem);
+ int align = MEM_ALIGN (mem);
rtx new_mem;
int old_cost = 0;
int new_cost = 0;
@@ -478,6 +479,7 @@ attempt_change (rtx new_addr, rtx inc_reg)
PUT_MODE (mem_tmp, mode);
XEXP (mem_tmp, 0) = new_addr;
+ set_mem_align (mem_tmp, align);
old_cost = (set_src_cost (mem, mode, speed)
+ set_rtx_cost (PATTERN (inc_insn.insn), speed));
--
1.8.3.1
