This patch moves the check for an overlapping byte to normalize_ref
from its callers, so that it's easier to convert to poly_ints later.
It's not really worth it on its own.
2017-10-23 Richard Sandiford <richard.sandif...@linaro.org>
gcc/
* tree-ssa-dse.c (normalize_ref): Check whether the ranges overlap
and return false if not.
(clear_bytes_written_by, live_bytes_read): Update accordingly.
Index: gcc/tree-ssa-dse.c
===================================================================
--- gcc/tree-ssa-dse.c 2017-10-23 11:41:23.587123840 +0100
+++ gcc/tree-ssa-dse.c 2017-10-23 11:47:41.546155781 +0100
@@ -137,13 +137,11 @@ valid_ao_ref_for_dse (ao_ref *ref)
&& (ref->size != -1));
}
-/* Normalize COPY (an ao_ref) relative to REF. Essentially when we are
- done COPY will only refer bytes found within REF.
+/* Try to normalize COPY (an ao_ref) relative to REF. Essentially when we are
+ done COPY will only refer bytes found within REF. Return true if COPY
+ is known to intersect at least one byte of REF. */
- We have already verified that COPY intersects at least one
- byte with REF. */
-
-static void
+static bool
normalize_ref (ao_ref *copy, ao_ref *ref)
{
/* If COPY starts before REF, then reset the beginning of
@@ -151,13 +149,22 @@ normalize_ref (ao_ref *copy, ao_ref *ref
number of bytes removed from COPY. */
if (copy->offset < ref->offset)
{
- copy->size -= (ref->offset - copy->offset);
+ HOST_WIDE_INT diff = ref->offset - copy->offset;
+ if (copy->size <= diff)
+ return false;
+ copy->size -= diff;
copy->offset = ref->offset;
}
+ HOST_WIDE_INT diff = copy->offset - ref->offset;
+ if (ref->size <= diff)
+ return false;
+
/* If COPY extends beyond REF, chop off its size appropriately. */
- if (copy->offset + copy->size > ref->offset + ref->size)
- copy->size -= (copy->offset + copy->size - (ref->offset + ref->size));
+ HOST_WIDE_INT limit = ref->size - diff;
+ if (copy->size > limit)
+ copy->size = limit;
+ return true;
}
/* Clear any bytes written by STMT from the bitmap LIVE_BYTES. The base
@@ -179,14 +186,10 @@ clear_bytes_written_by (sbitmap live_byt
if (valid_ao_ref_for_dse (&write)
&& operand_equal_p (write.base, ref->base, OEP_ADDRESS_OF)
&& write.size == write.max_size
- && ((write.offset < ref->offset
- && write.offset + write.size > ref->offset)
- || (write.offset >= ref->offset
- && write.offset < ref->offset + ref->size)))
- {
- normalize_ref (&write, ref);
- bitmap_clear_range (live_bytes,
- (write.offset - ref->offset) / BITS_PER_UNIT,
+ && normalize_ref (&write, ref))
+ {
+ HOST_WIDE_INT start = write.offset - ref->offset;
+ bitmap_clear_range (live_bytes, start / BITS_PER_UNIT,
write.size / BITS_PER_UNIT);
}
}
@@ -480,21 +483,20 @@ live_bytes_read (ao_ref use_ref, ao_ref
{
/* We have already verified that USE_REF and REF hit the same object.
Now verify that there's actually an overlap between USE_REF and REF. */
- if (ranges_overlap_p (use_ref.offset, use_ref.size, ref->offset, ref->size))
+ if (normalize_ref (&use_ref, ref))
{
- normalize_ref (&use_ref, ref);
+ HOST_WIDE_INT start = use_ref.offset - ref->offset;
+ HOST_WIDE_INT size = use_ref.size;
/* If USE_REF covers all of REF, then it will hit one or more
live bytes. This avoids useless iteration over the bitmap
below. */
- if (use_ref.offset <= ref->offset
- && use_ref.offset + use_ref.size >= ref->offset + ref->size)
+ if (start == 0 && size == ref->size)
return true;
/* Now check if any of the remaining bits in use_ref are set in LIVE. */
- unsigned int start = (use_ref.offset - ref->offset) / BITS_PER_UNIT;
- unsigned int end = ((use_ref.offset + use_ref.size) / BITS_PER_UNIT) -
1;
- return bitmap_bit_in_range_p (live, start, end);
+ return bitmap_bit_in_range_p (live, start / BITS_PER_UNIT,
+ (start + size - 1) / BITS_PER_UNIT);
}
return true;
}
