By propagating the value for the switch condition, LLVM can now build
lookup tables for code such as:
switch (x) {
case 1: return 5;
case 2: return 42;
case 3: case 4: case 5:
return x - 123;
default:
return 123;
}
Given that x is known for each case, "x - 123" becomes a constant for
cases 3, 4, and 5.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167115 91177308-0d34-0410-b5e6-96231b3b80d8
When the switch-to-lookup tables transform landed in SimplifyCFG, it
was pointed out that this could be inappropriate for some targets.
Since there was no way at the time for the pass to know anything about
the target, an awkward reverse-transform was added in CodeGenPrepare
that turned lookup tables back into switches for some targets.
This patch uses the new TargetTransformInfo to determine if a
switch should be transformed, and removes
CodeGenPrepare::ConvertLoadToSwitch.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167011 91177308-0d34-0410-b5e6-96231b3b80d8
The isValueEqualityComparison() guard at the top of SimplifySwitch()
only applies to some of the possible transformations.
The newer transformations work just fine on large switches, and the
check on predecessor count is nonsensical.
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We conservatively only check the first use to avoid walking long use chains.
This catches the common case of having both a load and a store to a pointer
supplied by a PHI node.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165232 91177308-0d34-0410-b5e6-96231b3b80d8
If the width is very large it gets truncated from uint64_t to uint32_t when
passed to TD->fitsInLegalInteger. The truncated value can fit in a register.
This manifested in massive memory usage or crashes (PR13946).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164784 91177308-0d34-0410-b5e6-96231b3b80d8
- Put statistics in alphabetical order
- Don't use getZextValue when building TableInt, just use APInts
- Introduce Create{Z,S}ExtOrTrunc in IRBuilder.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164696 91177308-0d34-0410-b5e6-96231b3b80d8
tables in bitmaps when they fit in a target-legal register.
This saves some space, and it also allows for building tables that would
otherwise be deemed too sparse.
One interesting case that this hits is example 7 from
http://blog.regehr.org/archives/320. We currently generate good code
for this when lowering the switch to the selection DAG: we build a
bitmask to decide whether to jump to one block or the other. My patch
will result in the same bitmask, but it removes the need for the jump,
as the return value can just be retrieved from the mask.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164684 91177308-0d34-0410-b5e6-96231b3b80d8
We already have HoistThenElseCodeToIf, this patch implements
SinkThenElseCodeToEnd. When END block has only two predecessors and each
predecessor terminates with unconditional branches, we compare instructions in
IF and ELSE blocks backwards and check whether we can sink the common
instructions down.
rdar://12191395
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two variables where the first variable is returned and the second
ignored.
I don't think this occurs in practice (other passes should have cleaned
up the unused phi node), but it should still be handled correctly.
Also make the logic for determining if we should return early less
sketchy.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164225 91177308-0d34-0410-b5e6-96231b3b80d8
Hanlde the case when we split the default edge if the default target has "icmp"
and unconditinal branch.
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destination.
Updated previous implementation to fix a case not covered:
// PBI: br i1 %x, TrueDest, BB
// BI: br i1 %y, TrueDest, FalseDest
The other case was handled correctly.
// PBI: br i1 %x, BB, FalseDest
// BI: br i1 %y, TrueDest, FalseDest
Also tried to use 64-bit arithmetic instead of APInt with scale to simplify the
computation. Let me know if you have other opinions about this.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163954 91177308-0d34-0410-b5e6-96231b3b80d8
the default target of the first switch is not the basic block the second switch
is in (PredDefault != BB).
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a pair of switch/branch where both depend on the value of the same variable and
the default case of the first switch/branch goes to the second switch/branch.
Code clean up and fixed a few issues:
1> handling the case where some cases of the 2nd switch are invalidated
2> correctly calculate the weight for the 2nd switch when it is a conditional eq
Testing case is modified from Alastair's original patch.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163635 91177308-0d34-0410-b5e6-96231b3b80d8
The lookup tables did not get built in a deterministic order.
This makes them get built in the order that the corresponding phi nodes
were found.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163305 91177308-0d34-0410-b5e6-96231b3b80d8
This adds a transformation to SimplifyCFG that attemps to turn switch
instructions into loads from lookup tables. It works on switches that
are only used to initialize one or more phi nodes in a common successor
basic block, for example:
int f(int x) {
switch (x) {
case 0: return 5;
case 1: return 4;
case 2: return -2;
case 5: return 7;
case 6: return 9;
default: return 42;
}
This speeds up the code by removing the hard-to-predict jump, and
reduces code size by removing the code for the jump targets.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163302 91177308-0d34-0410-b5e6-96231b3b80d8
another mechanical change accomplished though the power of terrible Perl
scripts.
I have manually switched some "s to 's to make escaping simpler.
While I started this to fix tests that aren't run in all configurations,
the massive number of tests is due to a really frustrating fragility of
our testing infrastructure: things like 'grep -v', 'not grep', and
'expected failures' can mask broken tests all too easily.
Essentially, I'm deeply disturbed that I can change the testsuite so
radically without causing any change in results for most platforms. =/
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This was done through the aid of a terrible Perl creation. I will not
paste any of the horrors here. Suffice to say, it require multiple
staged rounds of replacements, state carried between, and a few
nested-construct-parsing hacks that I'm not proud of. It happens, by
luck, to be able to deal with all the TCL-quoting patterns in evidence
in the LLVM test suite.
If anyone is maintaining large out-of-tree test trees, feel free to poke
me and I'll send you the steps I used to convert things, as well as
answer any painful questions etc. IRC works best for this type of thing
I find.
Once converted, switch the LLVM lit config to use ShTests the same as
Clang. In addition to being able to delete large amounts of Python code
from 'lit', this will also simplify the entire test suite and some of
lit's architecture.
Finally, the test suite runs 33% faster on Linux now. ;]
For my 16-hardware-thread (2x 4-core xeon e5520): 36s -> 24s
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159525 91177308-0d34-0410-b5e6-96231b3b80d8
- simplifycfg: invoke undef/null -> unreachable
- instcombine: invoke new -> invoke expect(0, 0) (an arbitrary NOOP intrinsic; only done if the allocated memory is unused, of course)
- verifier: allow invoke of intrinsics (to make the previous step work)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159146 91177308-0d34-0410-b5e6-96231b3b80d8
This patch extends FoldBranchToCommonDest to fold unconditional branches.
For unconditional branches, we fold them if it is easy to update the phi nodes
in the common successors.
rdar://10554090
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returns false in the event the computation feeding into the pointer is
unreachable, which maybe ought to be true -- but this is at least consistent
with undef->isDereferenceablePointer().) Fixes PR11825!
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present in the bottom of the CFG triangle, as the transformation isn't
ever valuable if the branch can't be eliminated.
Also, unify some heuristics between SimplifyCFG's multiple
if-converters, for consistency.
This fixes rdar://10627242.
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code can incorrectly move the load across a store. This never
happens in practice today, but only because the current
heuristics accidentally preclude it.
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For example,
if (a == b) {
if (a > b) // this is false
Fixes some of the issues on <rdar://problem/10554090>
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I think this is the last of autoupgrade that can be removed in 3.1.
Can the atomic upgrade stuff also go?
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