When an instruction only writes sub-registers, it is still necessary to
add an <imp-def> operand for the super-register. When reloading into a
virtual register, rewriting will add the operand, but when loading
directly into a virtual register, the <imp-def> operand is still
necessary.
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Based on a writeup originally by Greg Clayton.
Abuse div and pre tags horribly. Needs a bit more cleanup.
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The fpscr register contains both flags (set by FP operations/comparisons) and
control bits. The control bits (FPSCR) should be reserved, since they're always
available and needn't be defined before use. The flag bits (FPSCR_NZCV) should
like to be unreserved so they can be hoisted by MachineCSE. This fixes PR12165.
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With the new composite physical registers to represent arbitrary pairs
of DPR registers, we don't need the pseudo-registers anymore. Get rid of
a bunch of them that use DPR register pairs and just use the real
instructions directly instead.
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Specifically, remove the magic number when checking to see if the copy has a
glue operand and simplify the checking logic.
rdar://10930395
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This was testing the handling of sub-register coalescing followed by
remat. The original problem was caused by the extra <imp-def> operands
added by sub-register coalescing. Those <imp-def> operands are not
added any longer, and the test case passes even when the original patch
is reverted.
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In this update:
- I assumed neon2 does not imply vfpv4, but neon and vfpv4 imply neon2.
- I kept setting .fpu=neon-vfpv4 code attribute because that is what the
assembler understands.
Patch by Ana Pazos <apazos@codeaurora.org>
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This implicitly fixes a nasty bug in the GVN hashing (that thankfully
could only manifest as a performance bug): actually include the opcode
in the hash. The old code started the hash off with the opcode, but then
overwrote it with the type pointer.
Since this is likely to be pretty hot (GVN being already pretty
expensive) I've included a micro-optimization to just not bother with
the varargs hashing if they aren't present. I can't measure any change
in GVN performance due to this, even with a big test case like Duncan's
sqlite one. Everything I see is in the noise floor. That said, this
closes a loop hole for a potential scaling problem due to collisions if
the opcode were the differentiating aspect of the expression.
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hashing infrastructure. I wonder why we don't just use StringMap here,
and I may revisit the issue if I have time, but for now I'm just trying
to consolidate.
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complains about the truncation of a 64-bit constant to a 32-bit value
when size_t is 32-bits wide, but *only with static_cast*!!! The exact
signal that should *silence* such a warning, and in fact does silence it
with both GCC and Clang.
Anyways, this was causing grief for all the MSVC builds, so pointless
change made. Thanks to Nikola on IRC for confirming that this works.
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The first def of a virtual register cannot also read the register.
Assert on such bad machine code instead of trying to fix it.
TwoAddressInstructionPass should never create code like that.
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We are already setting <undef> flags, and that is good enough. The
<imp-def> operands don't mean anything any more.
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