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Speed up the tail duplication pass on the testcase below from 68.2s to 1.23s:
#define CL0(a) case a: f(); goto c; #define CL1(a) CL0(a##0) CL0(a##1) CL0(a##2) CL0(a##3) CL0(a##4) CL0(a##5) \ CL0(a##6) CL0(a##7) CL0(a##8) CL0(a##9) #define CL2(a) CL1(a##0) CL1(a##1) CL1(a##2) CL1(a##3) CL1(a##4) CL1(a##5) \ CL1(a##6) CL1(a##7) CL1(a##8) CL1(a##9) #define CL3(a) CL2(a##0) CL2(a##1) CL2(a##2) CL2(a##3) CL2(a##4) CL2(a##5) \ CL2(a##6) CL2(a##7) CL2(a##8) CL2(a##9) #define CL4(a) CL3(a##0) CL3(a##1) CL3(a##2) CL3(a##3) CL3(a##4) CL3(a##5) \ CL3(a##6) CL3(a##7) CL3(a##8) CL3(a##9) void f(); void a() { int b; c: switch (b) { CL4(1) } } This comes from GCC PR 15524 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17390 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -114,9 +114,14 @@ bool TailDup::shouldEliminateUnconditionalBranch(TerminatorInst *TI) {
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// with a single successor if the block has many other predecessors. This can
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// cause an N^2 explosion in CFG edges (and PHI node entries), as seen in
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// cases that have a large number of indirect gotos.
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if (DTI->getNumSuccessors() > 8)
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if (std::distance(PI, PE) * DTI->getNumSuccessors() > 128)
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return false;
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unsigned NumSuccs = DTI->getNumSuccessors();
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if (NumSuccs > 8) {
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unsigned TooMany = 128;
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if (NumSuccs >= TooMany) return false;
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TooMany = TooMany/NumSuccs;
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for (; PI != PE; ++PI)
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if (TooMany-- == 0) return false;
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}
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return true;
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}
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