From 340ecf207ffa2bc5b3abb4878c349ca196d698cc Mon Sep 17 00:00:00 2001 From: poonam Date: Fri, 28 Feb 2014 02:43:16 -0800 Subject: [PATCH] 8035283: Second phase of branch shortening doesn't account for loop alignment Summary: added missing check for loop padding case. Reviewed-by: kvn, jrose --- src/share/vm/opto/output.cpp | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/src/share/vm/opto/output.cpp b/src/share/vm/opto/output.cpp index f362669b5..9ddb26339 100644 --- a/src/share/vm/opto/output.cpp +++ b/src/share/vm/opto/output.cpp @@ -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; -- GitLab