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Use the libanalysis 'ConstantFoldLoadFromConstPtr' function

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instead of reinventing SCCP-specific logic.  This gives us
new powers.

llvm-svn: 85789
This commit is contained in:
Chris Lattner 2009-11-02 06:06:14 +00:00
parent 32acebedf7
commit 16b825e51f
2 changed files with 20 additions and 20 deletions
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29
lib/Transforms/Scalar/SCCP.cpp
View File

@ -28,6 +28,7 @@
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
@ -154,6 +155,7 @@ namespace {
/// Constant Propagation.
///
class SCCPSolver : public InstVisitor<SCCPSolver> {
const TargetData *TD;
DenseSet<BasicBlock*> BBExecutable;// The basic blocks that are executable
DenseMap<Value*, LatticeVal> ValueState; // The state each value is in.
@ -194,6 +196,7 @@ class SCCPSolver : public InstVisitor<SCCPSolver> {
typedef std::pair<BasicBlock*, BasicBlock*> Edge;
DenseSet<Edge> KnownFeasibleEdges;
public:
SCCPSolver(const TargetData *td) : TD(td) {}
/// MarkBlockExecutable - This method can be used by clients to mark all of
/// the blocks that are known to be intrinsically live in the processed unit.
@ -1109,16 +1112,15 @@ void SCCPSolver::visitStoreInst(StoreInst &SI) {
// global, we can replace the load with the loaded constant value!
void SCCPSolver::visitLoadInst(LoadInst &I) {
LatticeVal PtrVal = getValueState(I.getOperand(0));
if (PtrVal.isUndefined()) return; // The pointer is not resolved yet!
LatticeVal &IV = ValueState[&I];
if (IV.isOverdefined()) return;
if (PtrVal.isUndefined()) return; // The pointer is not resolved yet!
if (!PtrVal.isConstant() || I.isVolatile())
return markOverdefined(IV, &I);
Value *Ptr = PtrVal.getConstant();
Constant *Ptr = PtrVal.getConstant();
// load null -> null
if (isa<ConstantPointerNull>(Ptr) && I.getPointerAddressSpace() == 0)
@ -1126,11 +1128,7 @@ void SCCPSolver::visitLoadInst(LoadInst &I) {
// Transform load (constant global) into the value loaded.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
if (GV->isConstant()) {
if (GV->hasDefinitiveInitializer())
return markConstant(IV, &I, GV->getInitializer());
} else if (!TrackedGlobals.empty()) {
if (!TrackedGlobals.empty()) {
// If we are tracking this global, merge in the known value for it.
DenseMap<GlobalVariable*, LatticeVal>::iterator It =
TrackedGlobals.find(GV);
@ -1141,14 +1139,9 @@ void SCCPSolver::visitLoadInst(LoadInst &I) {
}
}
// Transform load (constantexpr_GEP global, 0, ...) into the value loaded.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
if (CE->getOpcode() == Instruction::GetElementPtr)
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
if (GV->isConstant() && GV->hasDefinitiveInitializer())
if (Constant *V =
ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
return markConstant(IV, &I, V);
// Transform load from a constant into a constant if possible.
if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, TD))
return markConstant(IV, &I, C);
// Otherwise we cannot say for certain what value this load will produce.
// Bail out.
@ -1530,7 +1523,7 @@ static void DeleteInstructionInBlock(BasicBlock *BB) {
//
bool SCCP::runOnFunction(Function &F) {
DEBUG(errs() << "SCCP on function '" << F.getName() << "'\n");
SCCPSolver Solver;
SCCPSolver Solver(getAnalysisIfAvailable<TargetData>());
// Mark the first block of the function as being executable.
Solver.MarkBlockExecutable(F.begin());
@ -1640,7 +1633,7 @@ static bool AddressIsTaken(GlobalValue *GV) {
}
bool IPSCCP::runOnModule(Module &M) {
SCCPSolver Solver;
SCCPSolver Solver(getAnalysisIfAvailable<TargetData>());
// Loop over all functions, marking arguments to those with their addresses
// taken or that are external as overdefined.

11
test/Transforms/SCCP/loadtest.ll
View File

@ -1,5 +1,6 @@
; This test makes sure that these instructions are properly constant propagated.
;
target datalayout = "e-p:32:32"
; RUN: opt < %s -sccp -S | not grep load
@ -20,7 +21,13 @@ define float @test2() {
define i32 @test3() {
%A = getelementptr [2 x { i32, float }]* @Y, i64 0, i64 0, i32 0 ; <i32*> [#uses=1]
%B = load i32* %A ; <i32> [#uses=1]
%B = load i32* %A
ret i32 %B
}
define i8 @test4() {
%A = bitcast i32* @X to i8*
%B = load i8* %A
ret i8 %B
}