move 'loading i32 from string' optimization from instcombine
to libanalysis. Instcombine shrinking... does this even
make sense???
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84840 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index da671c8..1f91ddf 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -24,13 +24,13 @@
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/LLVMContext.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/Target/TargetData.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
-#include "llvm/Target/TargetData.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/MathExtras.h"
-#include "llvm/GlobalVariable.h"
#include <cerrno>
#include <cmath>
using namespace llvm;
@@ -111,6 +111,35 @@
ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
return V;
}
+
+ // Instead of loading constant c string, use corresponding integer value
+ // directly if string length is small enough.
+ std::string Str;
+ if (TD && GetConstantStringInfo(CE->getOperand(0), Str) && !Str.empty()) {
+ unsigned len = Str.length();
+ const Type *Ty = cast<PointerType>(CE->getType())->getElementType();
+ unsigned numBits = Ty->getPrimitiveSizeInBits();
+ // Replace LI with immediate integer store.
+ if ((numBits >> 3) == len + 1) {
+ APInt StrVal(numBits, 0);
+ APInt SingleChar(numBits, 0);
+ if (TD->isLittleEndian()) {
+ for (signed i = len-1; i >= 0; i--) {
+ SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
+ StrVal = (StrVal << 8) | SingleChar;
+ }
+ } else {
+ for (unsigned i = 0; i < len; i++) {
+ SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
+ StrVal = (StrVal << 8) | SingleChar;
+ }
+ // Append NULL at the end.
+ SingleChar = 0;
+ StrVal = (StrVal << 8) | SingleChar;
+ }
+ return ConstantInt::get(CE->getContext(), StrVal);
+ }
+ }
}
return 0;
@@ -675,15 +704,15 @@
C = UndefValue::get(ATy->getElementType());
else
return 0;
- } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
- if (CI->getZExtValue() >= PTy->getNumElements())
+ } else if (const VectorType *VTy = dyn_cast<VectorType>(*I)) {
+ if (CI->getZExtValue() >= VTy->getNumElements())
return 0;
if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
C = CP->getOperand(CI->getZExtValue());
else if (isa<ConstantAggregateZero>(C))
- C = Constant::getNullValue(PTy->getElementType());
+ C = Constant::getNullValue(VTy->getElementType());
else if (isa<UndefValue>(C))
- C = UndefValue::get(PTy->getElementType());
+ C = UndefValue::get(VTy->getElementType());
else
return 0;
} else {