[Rapp-dev] RFC: fix insufficient alignment for benchmark run, bug #32835

[Hans-Peter Nilsson]

What do you think about this?  More details in the bug report.

I think adding a few comments as to the purpose of (adding) that
"offset" would help, but I'm not the right person for that.
Similarly the magic constant "256".  And why does RAPP_BMARK_VPAD
contribute just a few bytes when the name (Vertical PADding)
suggests it to be in lines, like vertical padding elsewhere in
RAPP?  Maybe it should be renamed something like
RAPP_BMARK_INITIAL_PAD, which seems slightly more accurate?

diff --git a/benchmark/rapp_benchmark.c b/benchmark/rapp_benchmark.c
index 2033026..826662a 100644
--- a/benchmark/rapp_benchmark.c
+++ b/benchmark/rapp_benchmark.c
@@ -534,9 +534,20 @@ rapp_bmark_setup(int width, int height)
     int pad_u8  = rapp_align(RAPP_BMARK_VPAD);
     int pad_bin = rapp_align((RAPP_BMARK_VPAD + 7) / 8);
     int offset  = RAPP_BMARK_HPAD*dim_u8 + pad_u8;
-    int size    = offset + 256 +
-                  RAPP_BMARK_ROWS*MAX(dim_u8*height + 2*RAPP_BMARK_HPAD,
-                                      rot_u8*width  + 2*RAPP_BMARK_HPAD);
+    int size;
+
+    /**
+     *  We perform an extra alignment of "offset", since it adjusts
+     *  pointers to types that might require alignment larger than
+     *  RAPP_ALIGNMEMT, e.g. uintmax_t being 64 bits and requiring
+     *  64-bit alignments on a target with 32-bit pointers and
+     *  RC_ALIGNMENT 4, such as sparc64 with the 32-bit ABI.
+     *  We assume that doubling the alignment is sufficient.
+     */
+    offset = 2*rapp_align(offset / 2 + 1);
+    size = offset + 256 +
+           RAPP_BMARK_ROWS*MAX(dim_u8*height + 2*RAPP_BMARK_HPAD,
+                               rot_u8*width  + 2*RAPP_BMARK_HPAD);
 
     rapp_bmark_data.dst     = rapp_malloc(size, 0);
     rapp_bmark_data.set     = rapp_malloc(size, 0);
diff --git a/compute/tune/benchmark/rc_benchmark.c 
b/compute/tune/benchmark/rc_benchmark.c
index be86159..7cfad8a 100644
--- a/compute/tune/benchmark/rc_benchmark.c
+++ b/compute/tune/benchmark/rc_benchmark.c
@@ -660,6 +660,16 @@ rc_bmark_setup(void *lib, int width, int height)
     dim_bin = (*align)((width + 7) / 8) + 2*pad;
     rot_u8  = (*align)(height);
     offset  = RC_BMARK_PADDING*dim_u8 + pad;
+
+    /**
+     *  We perform an extra alignment of "offset", since it adjusts
+     *  pointers to types that might require alignment larger than
+     *  RAPP_ALIGNMEMT, e.g. uintmax_t being 64 bits and requiring
+     *  64-bit alignments on a target with 32-bit pointers and
+     *  RC_ALIGNMENT 4, such as sparc64 with the 32-bit ABI.
+     *  We assume that doubling the alignment is sufficient.
+     */
+    offset  = 2*align(offset / 2 + 1);
     size    = MAX(dim_u8*(height + RC_BMARK_PADDING), rot_u8*width) + offset;
 
     rc_bmark_data.dst     = (*alloc)(size);
brgds, H-P