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author | Matthijs Kooijman <matthijs@stdin.nl> | 2008-06-17 12:20:24 +0000 |
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committer | Matthijs Kooijman <matthijs@stdin.nl> | 2008-06-17 12:20:24 +0000 |
commit | 2fbabf6e6dc61e0627b93a596bf13e272345c5e8 (patch) | |
tree | b7d728f7e4f2eb9a840e088c076b459be91e594a /lib/Transforms/IPO | |
parent | 906e423724f9f4409ff8725d0da8ecd09bec23cf (diff) | |
download | llvm-2fbabf6e6dc61e0627b93a596bf13e272345c5e8.tar.gz llvm-2fbabf6e6dc61e0627b93a596bf13e272345c5e8.tar.bz2 llvm-2fbabf6e6dc61e0627b93a596bf13e272345c5e8.tar.xz |
Learn IPConstProp to propagate arguments that are directly returned. Strictly
speaking these are not constant values. However, when a function always returns
one of its arguments, then from the point of view of each caller the return
value is constant (or at least a known value) and can be replaced.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52397 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/IPO')
-rw-r--r-- | lib/Transforms/IPO/IPConstantPropagation.cpp | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/lib/Transforms/IPO/IPConstantPropagation.cpp b/lib/Transforms/IPO/IPConstantPropagation.cpp index 0e654a50ee..54127f6a7a 100644 --- a/lib/Transforms/IPO/IPConstantPropagation.cpp +++ b/lib/Transforms/IPO/IPConstantPropagation.cpp @@ -145,6 +145,10 @@ bool IPCP::PropagateConstantsIntoArguments(Function &F) { // all callers that use those return values with the constant value. This will // leave in the actual return values and instructions, but deadargelim will // clean that up. +// +// Additionally if a function always returns one of its arguments directly, +// callers will be updated to use the value they pass in directly instead of +// using the return value. bool IPCP::PropagateConstantReturn(Function &F) { if (F.getReturnType() == Type::VoidTy) return false; // No return value. @@ -188,8 +192,8 @@ bool IPCP::PropagateConstantReturn(Function &F) { if (isa<UndefValue>(V)) continue; - // Try to see if all the rets return the same constant. - if (isa<Constant>(V)) { + // Try to see if all the rets return the same constant or argument. + if (isa<Constant>(V) || isa<Argument>(V)) { if (isa<UndefValue>(RV)) { // No value found yet? Try the current one. RetVals[i] = V; @@ -255,6 +259,11 @@ bool IPCP::PropagateConstantReturn(Function &F) { if (index != -1) { Value *New = RetVals[index]; if (New) { + if (Argument *A = dyn_cast<Argument>(New)) + // Was an argument returned? Then find the corresponding argument in + // the call instruction and use that. Add 1 to the argument number + // to skipp the first argument (the function itself). + New = Call->getOperand(A->getArgNo() + 1); Ins->replaceAllUsesWith(New); Ins->eraseFromParent(); } |