This function runs after all constant islands have been placed, and may
shrink some instructions to their 2-byte forms. This can actually cause
some constant pool entries to move out of range because of growing
alignment padding.
Treat instructions that may be shrunk the same as inline asm - they
erode the known alignment bits.
Also reinstate an old assertion in verify(). It is correct now that
basic block offsets include alignments.
Add a single large test case that will hopefully exercise many parts of
the constant island pass.
<rdar://problem/10670199>
llvm-svn: 147885
functional change in r147860 to use DW_TAG_label's instead TAG_subprogram's.
This only changes names and updates comments. No functional change.
llvm-svn: 147877
As the comment around 7746 says, it's better to use the x87 extended precision
here than SSE. And the generic code doesn't know how to do that. It also regains
the speed lost for the uint64_to_float.c testcase.
<rdar://problem/10669858>
llvm-svn: 147869
of several newly un-defaulted switches. This also helps optimizers
(including LLVM's) recognize that every case is covered, and we should
assume as much.
llvm-svn: 147861
assembly source when it generates the TAG_subprogram dwarf debug info for
the labels that have nothing between them as in this bit of assembly source:
% cat ZeroLength.s
_func1:
_func2:
nop
One solution would be to not emit the subsequent labels with the same address
and use the next label with a different address or the end of the section for
the AT_high_pc value of the TAG_subprogram.
Turns out in llvm-mc it is not possible in all cases to determine of two
symbols have the same value at the point we put out the TAG_subprogram dwarf
debug info.
So we will have llvm-mc instead of putting out TAG_subprogram's put out
DW_TAG_label's. And the DW_TAG_label does not have a AT_high_pc value which
avoids the problem.
This commit is only the functional change to make the diffs clear as to what is
really being changed. The next commit will be to clean up the names of such
things like MCGenDwarfSubprogramEntry to something like MCGenDwarfLabelEntry.
rdar://10666925
llvm-svn: 147860
define physical registers. It's currently very restrictive, only catching
cases where the CE is in an immediate (and only) predecessor. But it catches
a surprising large number of cases.
rdar://10660865
llvm-svn: 147827
These heuristics are sufficient for enabling IV chains by
default. Performance analysis has been done for i386, x86_64, and
thumbv7. The optimization is rarely important, but can significantly
speed up certain cases by eliminating spill code within the
loop. Unrolled loops are prime candidates for IV chains. In many
cases, the final code could still be improved with more target
specific optimization following LSR. The goal of this feature is for
LSR to make the best choice of induction variables.
Instruction selection may not completely take advantage of this
feature yet. As a result, there could be cases of slight code size
increase.
Code size can be worse on x86 because it doesn't support postincrement
addressing. In fact, when chains are formed, you may see redundant
address plus stride addition in the addressing mode. GenerateIVChains
tries to compensate for the common cases.
On ARM, code size increase can be mitigated by using postincrement
addressing, but downstream codegen currently misses some opportunities.
llvm-svn: 147826
On Thumb, the displacement computation hardware uses the address of the
current instruction rouned down to a multiple of 4. Include this
rounding in the UserOffset we compute for each instruction.
When inline asm is present, the instruction alignment may not be known.
Constrain the maximum displacement instead in that case.
This makes it possible for CreateNewWater() and OffsetIsInRange() to
agree about the valid displacements. When they disagree, infinite
looping happens.
As always, test cases for this stuff are insane.
<rdar://problem/10660175>
llvm-svn: 147825
After collecting chains, check if any should be materialized. If so,
hide the chained IV users from the LSR solver. LSR will only solve for
the head of the chain. GenerateIVChains will then materialize the
chained IV users by computing the IV relative to its previous value in
the chain.
In theory, chained IV users could be exposed to LSR's solver. This
would be considerably complicated to implement and I'm not aware of a
case where we need it. In practice it's more important to
intelligently prune the search space of nontrivial loops before
running the solver, otherwise the solver is often forced to prune the
most optimal solutions. Hiding the chained users does this well, so
that LSR is more likely to find the best IV for the chain as a whole.
llvm-svn: 147801
This collects a set of IV uses within the loop whose values can be
computed relative to each other in a sequence. Following checkins will
make use of this information.
llvm-svn: 147797
this substraction will result in small negative numbers at worst which
become very large positive numbers on assignment and are thus caught by
the <=4 check on the next line. The >0 check clearly intended to catch
these as negative numbers.
Spotted by inspection, and impossible to trigger given the shift widths
that can be used.
llvm-svn: 147773
