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* [gcc(refs/vendors/ARM/heads/morello)] Avoid trans-capability MEM_REF relaxation in SLSR
@ 2022-05-05 12:04 Matthew Malcomson
0 siblings, 0 replies; only message in thread
From: Matthew Malcomson @ 2022-05-05 12:04 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:730d6010d4773bba7255a5cd845c9d48826c4074
commit 730d6010d4773bba7255a5cd845c9d48826c4074
Author: Matthew Malcomson <matthew.malcomson@arm.com>
Date: Thu Mar 17 15:49:47 2022 +0000
Avoid trans-capability MEM_REF relaxation in SLSR
There is an optimisation in SLSR that takes a COMPONENT_REF (or similar)
whose base is a MEM_REF, and it splits that out into a MEM_REF using a
different offset (pre-calculated using known constants).
When performing this optimisation it uses the type of the offset for
different things, and ends up changing the type of the MEM_REF base to
the type of the offset.
This is problematic, since if the base is a capability type and the
offset is not this is throwing away the capability features.
Here we just disable this optimisation if the two types are not
compatible.
Diff:
---
gcc/gimple-ssa-strength-reduction.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/gcc/gimple-ssa-strength-reduction.c b/gcc/gimple-ssa-strength-reduction.c
index 3b7e1994abb..45f58df40df 100644
--- a/gcc/gimple-ssa-strength-reduction.c
+++ b/gcc/gimple-ssa-strength-reduction.c
@@ -993,6 +993,14 @@ restructure_reference (tree *pbase, tree *poffset, widest_int *pindex,
t1 = TREE_OPERAND (base, 0);
c1 = widest_int::from (mem_offset, SIGNED);
type = TREE_TYPE (TREE_OPERAND (base, 1));
+ /* MORELLO TODO HYBRID
+ * When splitting these MEM_REF's out we currently use the type of the
+ * offset rather than the type of the base pointer. If the base pointer and
+ * offset types differ in their capability nature then these types are not
+ * interchangeable. There is probably a way around this, but it's a simple
+ * and safe solution to avoid the optimisation in that case. */
+ if (!types_compatible_p (type, TREE_TYPE (t1)))
+ return false;
mult_op0 = TREE_OPERAND (offset, 0);
c3 = wi::to_widest (TREE_OPERAND (offset, 1));
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