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rtl-optimization/54052 - RTL SSA PHI insertion compile-time hog

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The following tries to address the PHI insertion compile-time hog in
RTL fwprop observed with the PR54052 testcase where the loop computing
the "unfiltered" set of variables possibly needing PHI nodes for each
block exhibits quadratic compile-time and memory-use.

It does so by pruning the local DEFs with LR_OUT of the block, removing
regs that can never be LR_IN (defined by this block) in the dominance
frontier.

	PR rtl-optimization/54052
	* rtl-ssa/blocks.cc (function_info::place_phis): Filter
	local defs by LR_OUT.
This commit is contained in:
Richard Biener 2024-02-19 11:10:50 +01:00
parent 78b72ee5a8
commit c7151283dc
1 changed files with 6 additions and 1 deletions
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7
gcc/rtl-ssa/blocks.cc
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@ -645,7 +645,12 @@ function_info::place_phis (build_info &bi)
if (bitmap_empty_p (&frontiers[b1]))
continue;
bitmap b1_def = &DF_LR_BB_INFO (BASIC_BLOCK_FOR_FN (m_fn, b1))->def;
// Defs in B1 that are possibly in LR_IN in the dominance frontier
// blocks.
auto_bitmap b1_def;
bitmap_and (b1_def, &DF_LR_BB_INFO (BASIC_BLOCK_FOR_FN (m_fn, b1))->def,
DF_LR_OUT (BASIC_BLOCK_FOR_FN (m_fn, b1)));
bitmap_iterator bmi;
unsigned int b2;
EXECUTE_IF_SET_IN_BITMAP (&frontiers[b1], 0, b2, bmi)