From: Chris Lattner Date: Mon, 1 Nov 2004 07:05:07 +0000 (+0000) Subject: Speed up the tail duplication pass on the testcase below from 68.2s to 1.23s: X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=7e54a01ddba2acfc46cc75b2a24cc3989e31f292;p=oota-llvm.git 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 --- diff --git a/lib/Transforms/Scalar/TailDuplication.cpp b/lib/Transforms/Scalar/TailDuplication.cpp index 85e1eac267e..545068b6dfb 100644 --- a/lib/Transforms/Scalar/TailDuplication.cpp +++ b/lib/Transforms/Scalar/TailDuplication.cpp @@ -114,9 +114,14 @@ bool TailDup::shouldEliminateUnconditionalBranch(TerminatorInst *TI) { // with a single successor if the block has many other predecessors. This can // cause an N^2 explosion in CFG edges (and PHI node entries), as seen in // cases that have a large number of indirect gotos. - if (DTI->getNumSuccessors() > 8) - if (std::distance(PI, PE) * DTI->getNumSuccessors() > 128) - return false; + unsigned NumSuccs = DTI->getNumSuccessors(); + if (NumSuccs > 8) { + unsigned TooMany = 128; + if (NumSuccs >= TooMany) return false; + TooMany = TooMany/NumSuccs; + for (; PI != PE; ++PI) + if (TooMany-- == 0) return false; + } return true; }