8035283: Second phase of branch shortening doesn't account for loop alignment
Summary: added missing check for loop padding case.
Reviewed-by: kvn, jrose
--- a/hotspot/src/share/vm/opto/output.cpp Wed Feb 26 11:33:34 2014 -0800
+++ b/hotspot/src/share/vm/opto/output.cpp Wed Feb 26 16:45:15 2014 -0800
@@ -344,6 +344,11 @@
uint* jmp_offset = NEW_RESOURCE_ARRAY(uint,nblocks);
uint* jmp_size = NEW_RESOURCE_ARRAY(uint,nblocks);
int* jmp_nidx = NEW_RESOURCE_ARRAY(int ,nblocks);
+
+ // Collect worst case block paddings
+ int* block_worst_case_pad = NEW_RESOURCE_ARRAY(int, nblocks);
+ memset(block_worst_case_pad, 0, nblocks * sizeof(int));
+
DEBUG_ONLY( uint *jmp_target = NEW_RESOURCE_ARRAY(uint,nblocks); )
DEBUG_ONLY( uint *jmp_rule = NEW_RESOURCE_ARRAY(uint,nblocks); )
@@ -460,6 +465,7 @@
last_avoid_back_to_back_adr += max_loop_pad;
}
blk_size += max_loop_pad;
+ block_worst_case_pad[i + 1] = max_loop_pad;
}
}
@@ -499,9 +505,16 @@
if (bnum > i) { // adjust following block's offset
offset -= adjust_block_start;
}
+
+ // This block can be a loop header, account for the padding
+ // in the previous block.
+ int block_padding = block_worst_case_pad[i];
+ assert(i == 0 || block_padding == 0 || br_offs >= block_padding, "Should have at least a padding on top");
// In the following code a nop could be inserted before
// the branch which will increase the backward distance.
- bool needs_padding = ((uint)br_offs == last_may_be_short_branch_adr);
+ bool needs_padding = ((uint)(br_offs - block_padding) == last_may_be_short_branch_adr);
+ assert(!needs_padding || jmp_offset[i] == 0, "padding only branches at the beginning of block");
+
if (needs_padding && offset <= 0)
offset -= nop_size;