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author | Owen Anderson <resistor@mac.com> | 2008-07-02 17:20:16 +0000 |
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committer | Owen Anderson <resistor@mac.com> | 2008-07-02 17:20:16 +0000 |
commit | f2aa160b357c98d8c37b69ea9775aa3e097d1319 (patch) | |
tree | bad306be76337b3a4dac25790e1644b4682642cb | |
parent | bee98c66c0c3d1f43244cdf237e572a9df031e40 (diff) | |
download | llvm-f2aa160b357c98d8c37b69ea9775aa3e097d1319.tar.gz llvm-f2aa160b357c98d8c37b69ea9775aa3e097d1319.tar.bz2 llvm-f2aa160b357c98d8c37b69ea9775aa3e097d1319.tar.xz |
A better fix for PR2503 that doesn't pessimize GVN in the presence of unreachable blocks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53032 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | lib/Analysis/MemoryDependenceAnalysis.cpp | 13 | ||||
-rw-r--r-- | lib/Transforms/Scalar/GVN.cpp | 5 | ||||
-rw-r--r-- | test/Transforms/GVN/2008-07-02-Unreachable.ll | 36 |
3 files changed, 41 insertions, 13 deletions
diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp index 1cd16bb06d..2012ab473c 100644 --- a/lib/Analysis/MemoryDependenceAnalysis.cpp +++ b/lib/Analysis/MemoryDependenceAnalysis.cpp @@ -19,7 +19,6 @@ #include "llvm/Instructions.h" #include "llvm/Function.h" #include "llvm/Analysis/AliasAnalysis.h" -#include "llvm/Analysis/Dominators.h" #include "llvm/Support/CFG.h" #include "llvm/Support/CommandLine.h" #include "llvm/Target/TargetData.h" @@ -83,7 +82,6 @@ void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesAll(); AU.addRequiredTransitive<AliasAnalysis>(); AU.addRequiredTransitive<TargetData>(); - AU.addRequiredTransitive<DominatorTree>(); } /// getCallSiteDependency - Private helper for finding the local dependencies @@ -224,17 +222,6 @@ void MemoryDependenceAnalysis::nonLocalHelper(Instruction* query, continue; } - // Don't recur upwards if the current block is unreachable. - // Instead, mark it as having no dependency on this path, - // which will block optzns from occuring. For this reason, - // eliminating unreachable blocks before running a memdep - // based optimization is recommended. - DominatorTree& DT = getAnalysis<DominatorTree>(); - if (!DT.isReachableFromEntry(BB)) { - resp.insert(std::make_pair(BB, None)); - continue; - } - // If we didn't find anything, recurse on the precessors of this block // Only do this for blocks with a small number of predecessors. bool predOnStack = false; diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index 5564dbde1b..590227c27f 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/lib/Transforms/Scalar/GVN.cpp @@ -808,6 +808,11 @@ Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig, DenseMap<BasicBlock*, Value*>::iterator V = Phis.find(BB); if (V != Phis.end() && !top_level) return V->second; + if (!getAnalysis<DominatorTree>().isReachableFromEntry(BB)) { + Phis[BB] = UndefValue::get(orig->getType()); + return UndefValue::get(orig->getType()); + } + BasicBlock* singlePred = BB->getSinglePredecessor(); if (singlePred) { Value *ret = GetValueForBlock(singlePred, orig, Phis); diff --git a/test/Transforms/GVN/2008-07-02-Unreachable.ll b/test/Transforms/GVN/2008-07-02-Unreachable.ll new file mode 100644 index 0000000000..0052daf7c5 --- /dev/null +++ b/test/Transforms/GVN/2008-07-02-Unreachable.ll @@ -0,0 +1,36 @@ +; RUN: llvm-as < %s | opt -gvn | llvm-dis | grep undef +; PR2503 +target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128" +target triple = "i686-apple-darwin9.3.0" +@g_3 = external global i8 ; <i8*> [#uses=2] + +define i32 @func_1() nounwind { +entry: + br i1 false, label %ifelse, label %ifthen + +ifthen: ; preds = %entry + br label %ifend + +ifelse: ; preds = %entry + %tmp3 = load i8* @g_3 ; <i8> [#uses=0] + br label %forcond.thread + +forcond.thread: ; preds = %ifelse + br label %afterfor + +forcond: ; preds = %forinc + br i1 false, label %afterfor, label %forbody + +forbody: ; preds = %forcond + br label %forinc + +forinc: ; preds = %forbody + br label %forcond + +afterfor: ; preds = %forcond, %forcond.thread + %tmp10 = load i8* @g_3 ; <i8> [#uses=0] + br label %ifend + +ifend: ; preds = %afterfor, %ifthen + ret i32 0 +} |