We've been seeing a bunch of new failures in the *libffi* testsuite on ARM Linux
(arm-none-linux-gnueabi, arm-none-linux-gnueabihf), following this one-liner
fix. I've reduced the testcase down to the attached (including removing any
dependency on libffi); with gcc r221347, this prints the expected
7 8 9
whereas with gcc r221348, instead it prints
0 8 0
The action of r221348 is to change the alignment of a mem_ref, and a var_decl of
b1, from 32 to 64; both have type
type <record_type 0x2b9b8d428d20 cls_struct_16byte sizes-gimplified type_0 BLK
size <integer_cst 0x2b9b8d3720a8 constant 192>
unit size <integer_cst 0x2b9b8d372078 constant 24>
align 64 symtab 0 alias set 1 canonical type 0x2b9b8d428d20
fields <field_decl 0x2b9b8d42b098 a type <integer_type 0x2b9b8d092690
int>
SI file reduced.c line 12 col 7
size <integer_cst 0x2b9b8d08eeb8 constant 32>
unit size <integer_cst 0x2b9b8d08eed0 constant 4>
align 32 offset_align 64
offset <integer_cst 0x2b9b8d08eee8 constant 0>
bit offset <integer_cst 0x2b9b8d08ef48 constant 0> context
<record_type 0x2b9b8d428d20 cls_struct_16byte> chain <field_decl 0x2b9b8d42b130
b>> context <translation_unit_decl 0x2b9b8d4232d0 D.6070>
pointer_to_this <pointer_type 0x2b9b8d42d0a8> chain <type_decl
0x2b9b8d42b000 D.6044>>
The tree-optimized output is the same with both compilers (as this does not
mention alignment); the expand output differs.
Still investigating...
--Alan
Richard Biener wrote:
This fixes a vectorizer testcase regression on powerpc where SRA
drops alignment info unnecessarily.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2015-03-11 Richard Biener <[email protected]>
PR tree-optimization/65310
* tree-sra.c (build_ref_for_offset): Also preserve larger
alignment.
Index: gcc/tree-sra.c
===================================================================
--- gcc/tree-sra.c (revision 221324)
+++ gcc/tree-sra.c (working copy)
@@ -1597,7 +1597,7 @@ build_ref_for_offset (location_t loc, tr
misalign = (misalign + offset) & (align - 1);
if (misalign != 0)
align = (misalign & -misalign);
- if (align < TYPE_ALIGN (exp_type))
+ if (align != TYPE_ALIGN (exp_type))
exp_type = build_aligned_type (exp_type, align);
mem_ref = fold_build2_loc (loc, MEM_REF, exp_type, base, off);
