This code:
float floatingPointComparison(float x, float y) {
double product = (double)x * y;
if (product == 0.0)
return product;
return product - 1.0;
}
produces this:
_floatingPointComparison:
0000000000000000 cvtss2sd %xmm1,%xmm1
0000000000000004 cvtss2sd %xmm0,%xmm0
0000000000000008 mulsd %xmm1,%xmm0
000000000000000c pxor %xmm1,%xmm1
0000000000000010 ucomisd %xmm1,%xmm0
0000000000000014 jne 0x00000004
0000000000000016 jp 0x00000002
0000000000000018 jmp 0x00000008
000000000000001a addsd 0x00000006(%rip),%xmm0
0000000000000022 cvtsd2ss %xmm0,%xmm0
0000000000000026 ret
The "jne/jp/jmp" sequence can be reduced to this instead:
_floatingPointComparison:
0000000000000000 cvtss2sd %xmm1,%xmm1
0000000000000004 cvtss2sd %xmm0,%xmm0
0000000000000008 mulsd %xmm1,%xmm0
000000000000000c pxor %xmm1,%xmm1
0000000000000010 ucomisd %xmm1,%xmm0
0000000000000014 jp 0x00000002
0000000000000016 je 0x00000008
0000000000000018 addsd 0x00000006(%rip),%xmm0
0000000000000020 cvtsd2ss %xmm0,%xmm0
0000000000000024 ret
for a savings of 2 bytes.
This xform can happen when we recognize that jne and jp jump to the same "true"
MBB, the unconditional jump would jump to the "false" MBB, and the "true" branch
is the fall-through MBB.
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an undef value. This is only going to come up for bugpoint-reduced tests --
correct programs will not access memory at undefined addresses -- so it's not
worth the effort of doing anything more aggressive.
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These instructions technically define AL,AH, but a trick in X86ISelDAGToDAG
reads AX in order to avoid reading AH with a REX instruction.
Fix PR6489.
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IF(condition(value)):
If the value satisfies the condition, the line is processed by lit; otherwise
it is skipped. A test with no unignored directives is resolved as Unsupported.
The test suite is responsible for defining conditions; conditions are unary
functions over strings. I've defined two conditions in the LLVM test suite,
TARGET (with values like those in TARGETS_TO_BUILD) and BINDING (with values
like those in llvm_bindings). So for example you can write:
IF(BINDING(ocaml)): RUN: %blah %s -o -
and the RUN line will only execute if LLVM was configured with the ocaml
bindings.
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transformation much more careful. Truncating binary '01' to '1' sounds like it's
safe until you realize that it switched from positive to negative under a signed
interpretation, and that depends on the icmp predicate.
Also a few miscellaneous cleanups.
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long test(long x) { return (x & 123124) | 3; }
Currently compiles to:
_test:
orl $3, %edi
movq %rdi, %rax
andq $123127, %rax
ret
This is because instruction and DAG combiners canonicalize
(or (and x, C), D) -> (and (or, D), (C | D))
However, this is only profitable if (C & D) != 0. It gets in the way of the
3-addressification because the input bits are known to be zero.
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CopyToReg/CopyFromReg/INLINEASM. These are annoying because
they have the same opcode before an after isel. Fix this by
setting their NodeID to -1 to indicate that they are selected,
just like what automatically happens when selecting things that
end up being machine nodes.
With that done, give IsLegalToFold a new flag that causes it to
ignore chains. This lets the HandleMergeInputChains routine be
the one place that validates chains after a match is successful,
enabling the new hotness in chain processing. This smarter
chain processing eliminates the need for "PreprocessRMW" in the
X86 and MSP430 backends and enables MSP to start matching it's
multiple mem operand instructions more aggressively.
I currently #if out the dead code in the X86 backend and MSP
backend, I'll remove it for real in a follow-on patch.
The testcase changes are:
test/CodeGen/X86/sse3.ll: we generate better code
test/CodeGen/X86/store_op_load_fold2.ll: PreprocessRMW was
miscompiling this before, we now generate correct code
Convert it to filecheck while I'm at it.
test/CodeGen/MSP430/Inst16mm.ll: Add a testcase for mem/mem
folding to make anton happy. :)
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by loop depth and emit loop-invariant subexpressions outside of loops.
This speeds up MultiSource/Applications/viterbi and others.
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was that we weren't properly handling the case when interior
nodes of a matched pattern become dead after updating chain
and flag uses. Now we handle this explicitly in
UpdateChainsAndFlags.
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stuff now that we don't care about emulating the old broken
behavior of the old isel. This eliminates the
'CheckChainCompatible' check (along with IsChainCompatible) which
did an incorrect and inefficient scan *up* the chain nodes which
happened as the pattern was being formed and does the validation
at the end in HandleMergeInputChains when it forms a structural
pattern. This scans "down" the graph, which means that it is
quickly bounded by nodes already selected. This also handles
token factors that get "trapped" in the dag.
Removing the CheckChainCompatible nodes also shrinks the
generated tables by about 6K for X86 (down to 83K).
There are two pieces remaining before I can nuke PreprocessRMW:
1. I xfailed a test because we're now producing worse code in a
case that has nothing to do with the change: it turns out that
our use of MorphNodeTo will leave dead nodes in the graph
which (depending on how the graph is walked) end up causing
bogus uses of chains and blocking matches. This is really
bad for other reasons, so I'll fix this in a follow-up patch.
2. CheckFoldableChainNode needs to be improved to handle the TF.
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ordered correctly. Previously it would get in trouble when
two patterns were too similar and give them nondet ordering.
We force this by using the record ID order as a fallback.
The testsuite diff is due to alpha patterns being ordered
slightly differently, the change is a semantic noop afaict:
< lda $0,-100($16)
---
> subq $16,100,$0
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