[llvm-commits] [llvm] r85789 - in /llvm/trunk: lib/Transforms/Scalar/SCCP.cpp test/Transforms/SCCP/loadtest.ll

[Chris Lattner]

Author: lattner
Date: Mon Nov  2 00:06:14 2009
New Revision: 85789

URL: http://llvm.org/viewvc/llvm-project?rev=85789&view=rev
Log:
Use the libanalysis 'ConstantFoldLoadFromConstPtr' function
instead of reinventing SCCP-specific logic.  This gives us
new powers.

Modified:
    llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
    llvm/trunk/test/Transforms/SCCP/loadtest.ll

Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SCCP.cpp?rev=85789&r1=85788&r2=85789&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Mon Nov  2 00:06:14 2009
@@ -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 @@
 /// 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 @@
   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 @@
 // 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 @@
   
   // 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 @@
     }
   }
 
-  // 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 @@
 //
 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 @@
 }
 
 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.

Modified: llvm/trunk/test/Transforms/SCCP/loadtest.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SCCP/loadtest.ll?rev=85789&r1=85788&r2=85789&view=diff

==============================================================================
--- llvm/trunk/test/Transforms/SCCP/loadtest.ll (original)
+++ llvm/trunk/test/Transforms/SCCP/loadtest.ll Mon Nov  2 00:06:14 2009
@@ -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 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
+}
+