a cast immediately before a PHI node.
This fixes Regression/CodeGen/Generic/2006-05-06-GEP-Cast-Sink-Crash.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28143 91177308-0d34-0410-b5e6-96231b3b80d8
of cross-block live ranges, and allows the bb-at-a-time selector to always
coallesce these away, at isel time.
This reduces the load on the coallescer and register allocator. For example
on a codec on X86, we went from:
1643 asm-printer - Number of machine instrs printed
419 liveintervals - Number of loads/stores folded into instructions
1144 liveintervals - Number of identity moves eliminated after coalescing
1022 liveintervals - Number of interval joins performed
282 liveintervals - Number of intervals after coalescing
1304 liveintervals - Number of original intervals
86 regalloc - Number of times we had to backtrack
1.90232 regalloc - Ratio of intervals processed over total intervals
40 spiller - Number of values reused
182 spiller - Number of loads added
121 spiller - Number of stores added
132 spiller - Number of register spills
6 twoaddressinstruction - Number of instructions commuted to coalesce
360 twoaddressinstruction - Number of two-address instructions
to:
1636 asm-printer - Number of machine instrs printed
403 liveintervals - Number of loads/stores folded into instructions
1155 liveintervals - Number of identity moves eliminated after coalescing
1033 liveintervals - Number of interval joins performed
279 liveintervals - Number of intervals after coalescing
1312 liveintervals - Number of original intervals
76 regalloc - Number of times we had to backtrack
1.88998 regalloc - Ratio of intervals processed over total intervals
1 spiller - Number of copies elided
41 spiller - Number of values reused
191 spiller - Number of loads added
114 spiller - Number of stores added
128 spiller - Number of register spills
4 twoaddressinstruction - Number of instructions commuted to coalesce
356 twoaddressinstruction - Number of two-address instructions
On this testcase, this change provides a modest reduction in spill code,
regalloc iterations, and total instructions emitted. It increases the number
of register coallesces.
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scheduler can go into a "vertical mode" (i.e. traversing up the two-address
chain, etc.) when the register pressure is low.
This does seem to reduce the number of spills in the cases I've looked at. But
with x86, it's no guarantee the performance of the code improves.
It can be turned on with -sched-vertically option.
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not be 100% dense. Increase the minimum threshold for the number of cases
in a switch statement from 4 to 6 in order to create a jump table.
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the heuristic to further reduce spills for several test cases. (Note, it may
not necessarily translate to runtime win!)
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up the schedule. This helps code that looks like this:
loads ...
computations (first set) ...
stores (first set) ...
loads
computations (seccond set) ...
stores (seccond set) ...
Without this change, the stores and computations are more likely to
interleave:
loads ...
loads ...
computations (first set) ...
computations (second set) ...
computations (first set) ...
stores (first set) ...
computations (second set) ...
stores (stores set) ...
This can increase the number of spills if we are unlucky.
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x86 and ppc for 100% dense switch statements when relocations are non-PIC.
This support will be extended and enhanced in the coming days to support
PIC, and less dense forms of jump tables.
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llvm-gcc4 boostrap. Whenever a node is deleted by the dag combiner, it
*must* be returned by the visit function, or the dag combiner will not
know that the node has been processed (and will, e.g., send it to the
target dag combine xforms).
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DAG combiner can turn a VAND V, <-1, 0, -1, -1>, i.e. vector clear elements,
into a vector shuffle with a zero vector. It only does so when TLI tells it
the xform is profitable.
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