Apart from being slightly cheaper, this fixes a real bug that hits 32 bit
linux systems. When passing a file larger than 2G to be linked (which isn't
that uncommon with large projects such as WebKit), clang's driver checks
if the file exists but the file size doesn't fit in an off_t and stat(2)
fails with EOVERFLOW. Clang then says that the file doesn't exist instead
of passing it to the linker.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157891 91177308-0d34-0410-b5e6-96231b3b80d8
It was renamed in gcc/gas a while ago and causes all kinds of
confusion because it was named differently in llvm and clang.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157745 91177308-0d34-0410-b5e6-96231b3b80d8
This also required making recursive simplifications until
nothing changes or a hard limit (currently 3) is hit.
With the simplification in place indvars can canonicalize
loops of the form
for (unsigned i = 0; i < a-b; ++i)
into
for (unsigned i = 0; i != a-b; ++i)
which used to fail because SCEV created a weird umax expr
for the backedge taken count.
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This required light surgery on the assembler and disassembler
because the instructions use an uncommon encoding. They are
the only two instructions in x86 that use register operands
and two immediates.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157634 91177308-0d34-0410-b5e6-96231b3b80d8
The test case feeds the following into InstCombine's visitSelect:
%tobool8 = icmp ne i32 0, 0
%phitmp = select i1 %tobool8, i32 3, i32 0
Then instcombine replaces the right side of the switch with 0, doesn't notice
that nothing changes and tries again indefinitely.
This fixes PR12897.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157587 91177308-0d34-0410-b5e6-96231b3b80d8
The only missing part is insert(), which uses a pair of parameters and I haven't
figured out how to convert it to rvalue references. It's now possible to use a
DenseMap with std::unique_ptr values :)
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This is obviosly right but I don't see how to do this with proper vector
iterators without building a horrible mess of workarounds.
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SimplifyCFG tends to form a lot of 2-3 case switches when merging branches. Move
the most likely condition to the front so it is checked first and the others can
be skipped. This is currently not as effective as it could be because SimplifyCFG
destroys profiling metadata when merging branches and switches. Merging branch
weight metadata is tricky though.
This code touches at most 3 cases so I didn't use a proper sorting algorithm.
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There should be no difference in the resulting binary, given a sufficiently
smart compiler. However we already had compiler timeouts on the generated
code in Intrinsics.gen, this hopefully makes the lives of slow buildbots a
little easier.
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Otherwise just looking up a value in the map requires creating a VH, adding it to the use lists and destroying it again.
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The primitive conservative heuristic seems to give a slight overall
improvement while not regressing stuff. Make it available to wider
testing. If you notice any speed regressions (or significant code
size regressions) let me know!
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This came up when a change in block placement formed a cmov and slowed down a
hot loop by 50%:
ucomisd (%rdi), %xmm0
cmovbel %edx, %esi
cmov is a really bad choice in this context because it doesn't get branch
prediction. If we emit it as a branch, an out-of-order CPU can do a better job
(if the branch is predicted right) and avoid waiting for the slow load+compare
instruction to finish. Of course it won't help if the branch is unpredictable,
but those are really rare in practice.
This patch uses a dumb conservative heuristic, it turns all cmovs that have one
use and a direct memory operand into branches. cmovs usually save some code
size, so we disable the transform in -Os mode. In-Order architectures are
unlikely to benefit as well, those are included in the
"predictableSelectIsExpensive" flag.
It would be better to reuse branch probability info here, but BPI doesn't
support select instructions currently. It would make sense to use the same
heuristics as the if-converter pass, which does the opposite direction of this
transform.
Test suite shows a small improvement here and there on corei7-level machines,
but the actual results depend a lot on the used microarchitecture. The
transformation is currently disabled by default and available by passing the
-enable-cgp-select2branch flag to the code generator.
Thanks to Chandler for the initial test case to him and Evan Cheng for providing
me with comments and test-suite numbers that were more stable than mine :)
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This will be used to determine whether it's profitable to turn a select into a
branch when the branch is likely to be predicted.
Currently enabled for everything but Atom on X86 and Cortex-A9 devices on ARM.
I'm not entirely happy with the name of this flag, suggestions welcome ;)
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This way we can enable the POD-like class optimization for a lot more classes,
saving ~120k of code in clang/i386/Release+Asserts when selfhosting.
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* Model FPSW (the FPU status word) as a register.
* Add ISel patterns for the FUCOM*, FNSTSW and SAHF instructions.
* During Legalize/Lowering, build a node sequence to transfer the comparison
result from FPSW into EFLAGS. If you're wondering about the right-shift: That's
an implicit sub-register extraction (%ax -> %ah) which is handled later on by
the instruction selector.
Fixes PR6679. Patch by Christoph Erhardt!
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It set NumLowBitAvailable = 3 which may not be true on all platforms. We only
ever use 2 bits (the default) so this assumption can be safely removed
Should fix PR12612.
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DenseMap's hash function uses slightly more entropy and reduces hash collisions
significantly. I also experimented with Hashing.h, but it didn't gave a lot of
improvement while being much more expensive to compute.
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To be used in printing unprintable source in clang diagnostics.
Patch by Seth Cantrell, with a minor fix for mingw by me.
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As an example, attach range info to the "invalid instruction" message:
$ clang -arch arm -c asm.c
asm.c:2:11: error: invalid instruction
__asm__("foo r0");
^
<inline asm>:1:2: note: instantiated into assembly here
foo r0
^~~
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- Don't copy offsets into HashData, the underlying vector won't change once the table is finalized.
- Allocate HashData and HashDataContents in a BumpPtrAllocator.
- Allocate string map entries in the same allocator.
- Random cleanups.
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FoldingSet is implemented as a chained hash table. When there is a hash
collision during insertion, which is common as we fill the table until a
load factor of 2.0 is hit, we walk the chained elements, comparing every
operand with the new element's operands. This can be very expensive if the
MDNode has many operands.
We sacrifice a word of space in MDNode to cache the full hash value, reducing
compares on collision to a minimum. MDNode grows from 28 to 32 bytes + operands
on x86. On x86_64 the new bits fit nicely into existing padding, not growing
the struct at all.
The actual speedup depends a lot on the test case and is typically between
1% and 2% for C++ code with clang -c -O0 -g.
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Benjamin Kramer