6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-06-24 08:24:33 +00:00
Code Issues Projects Releases Wiki Activity

add the ability to get a rewritten value from the middle of a block,

Browse Source 
not just at the end.  Add a big comment explaining when this could
be useful (which never happens for jump threading).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83741 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2009-10-10 23:00:11 +00:00
parent 5fb107287f
commit 1a8d4de397
2 changed files with 119 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

30
include/llvm/Transforms/Utils/SSAUpdater.h
View File

@ -48,16 +48,40 @@ public:
/// updates. ProtoValue is the value used to name PHI nodes.
void Initialize(Value *ProtoValue);
/// AddAvailableValue - Indicate that a rewritten value is available in the
/// specified block with the specified value.
/// AddAvailableValue - Indicate that a rewritten value is available at the
/// end of the specified block with the specified value.
void AddAvailableValue(BasicBlock *BB, Value *V);
/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
/// live at the end of the specified block.
Value *GetValueAtEndOfBlock(BasicBlock *BB);
/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
/// is live in the middle of the specified block.
///
/// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
/// important case: if there is a definition of the rewritten value after the
/// 'use' in BB. Consider code like this:
///
/// X1 = ...
/// SomeBB:
/// use(X)
/// X2 = ...
/// br Cond, SomeBB, OutBB
///
/// In this case, there are two values (X1 and X2) added to the AvailableVals
/// set by the client of the rewriter, and those values are both live out of
/// their respective blocks. However, the use of X happens in the *middle* of
/// a block. Because of this, we need to insert a new PHI node in SomeBB to
/// merge the appropriate values, and this value isn't live out of the block.
///
Value *GetValueInMiddleOfBlock(BasicBlock *BB);
/// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
/// which use their value in the corresponding predecessor.
/// which use their value in the corresponding predecessor. Note that this
/// will not work if the use is supposed to be rewritten to a value defined in
/// the same block as the use, but above it. Any 'AddAvailableValue's added
/// for the use's block will be considered to be below it.
void RewriteUse(Use &U);
private: