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8035283: Second phase of branch shortening doesn't account for loop alignment

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Added missing check for loop padding case.

Reviewed-by: kvn, jrose
This commit is contained in:
Igor Veresov 2014-02-26 16:45:15 -08:00
parent c01a8b9263
commit 2c99a4ef9f
1 changed files with 14 additions and 1 deletions
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15
hotspot/src/share/vm/opto/output.cpp
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@ -344,6 +344,11 @@ void Compile::shorten_branches(uint* blk_starts, int& code_size, int& reloc_size
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 @@ void Compile::shorten_branches(uint* blk_starts, int& code_size, int& reloc_size
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 @@ void Compile::shorten_branches(uint* blk_starts, int& code_size, int& reloc_size
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;