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author | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2010-02-05 22:03:18 +0000 |
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committer | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2010-02-05 22:03:18 +0000 |
commit | 58e9ee85fda5083e2eea987917e8eab6ba31fe5e (patch) | |
tree | 542d47cbb2c02e5971df3c80b71b290118bd7877 /lib/Transforms/Scalar | |
parent | 00cb3fe786855ce6545234bc3430223eb9272206 (diff) | |
download | external_llvm-58e9ee85fda5083e2eea987917e8eab6ba31fe5e.zip external_llvm-58e9ee85fda5083e2eea987917e8eab6ba31fe5e.tar.gz external_llvm-58e9ee85fda5083e2eea987917e8eab6ba31fe5e.tar.bz2 |
Teach SimplifyCFG about magic pointer constants.
Weird code sometimes uses pointer constants other than null. This patch
teaches SimplifyCFG to build switch instructions in those cases.
Code like this:
void f(const char *x) {
if (!x)
puts("null");
else if ((uintptr_t)x == 1)
puts("one");
else if (x == (char*)2 || x == (char*)3)
puts("two");
else if ((intptr_t)x == 4)
puts("four");
else
puts(x);
}
Now becomes a switch:
define void @f(i8* %x) nounwind ssp {
entry:
%magicptr23 = ptrtoint i8* %x to i64 ; <i64> [#uses=1]
switch i64 %magicptr23, label %if.else16 [
i64 0, label %if.then
i64 1, label %if.then2
i64 2, label %if.then9
i64 3, label %if.then9
i64 4, label %if.then14
]
Note that LLVM's own DenseMap uses magic pointers.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95439 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/Scalar')
-rw-r--r-- | lib/Transforms/Scalar/SimplifyCFGPass.cpp | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/lib/Transforms/Scalar/SimplifyCFGPass.cpp index 43447de..62f34a2 100644 --- a/lib/Transforms/Scalar/SimplifyCFGPass.cpp +++ b/lib/Transforms/Scalar/SimplifyCFGPass.cpp @@ -30,6 +30,7 @@ #include "llvm/Attributes.h" #include "llvm/Support/CFG.h" #include "llvm/Pass.h" +#include "llvm/Target/TargetData.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/Statistic.h" @@ -261,7 +262,7 @@ static bool MergeEmptyReturnBlocks(Function &F) { /// IterativeSimplifyCFG - Call SimplifyCFG on all the blocks in the function, /// iterating until no more changes are made. -static bool IterativeSimplifyCFG(Function &F) { +static bool IterativeSimplifyCFG(Function &F, const TargetData *TD) { bool Changed = false; bool LocalChange = true; while (LocalChange) { @@ -271,7 +272,7 @@ static bool IterativeSimplifyCFG(Function &F) { // if they are unneeded... // for (Function::iterator BBIt = ++F.begin(); BBIt != F.end(); ) { - if (SimplifyCFG(BBIt++)) { + if (SimplifyCFG(BBIt++, TD)) { LocalChange = true; ++NumSimpl; } @@ -285,10 +286,11 @@ static bool IterativeSimplifyCFG(Function &F) { // simplify the CFG. // bool CFGSimplifyPass::runOnFunction(Function &F) { + const TargetData *TD = getAnalysisIfAvailable<TargetData>(); bool EverChanged = RemoveUnreachableBlocksFromFn(F); EverChanged |= MergeEmptyReturnBlocks(F); - EverChanged |= IterativeSimplifyCFG(F); - + EverChanged |= IterativeSimplifyCFG(F, TD); + // If neither pass changed anything, we're done. if (!EverChanged) return false; @@ -299,11 +301,11 @@ bool CFGSimplifyPass::runOnFunction(Function &F) { // RemoveUnreachableBlocksFromFn doesn't do anything. if (!RemoveUnreachableBlocksFromFn(F)) return true; - + do { - EverChanged = IterativeSimplifyCFG(F); + EverChanged = IterativeSimplifyCFG(F, TD); EverChanged |= RemoveUnreachableBlocksFromFn(F); } while (EverChanged); - + return true; } |