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1. "Upgrage" comments.
2. Using zero-extended value of Scale and unsigned division is safe provided that Scale doesn't have the sign bit set. Previously these 2 instructions: %p = bitcast [100 x {i8,i8,i8}]* %x to i8* %q = getelementptr i8* %p, i32 -4 were combined into: %q = getelementptr [100 x { i8, i8, i8 }]* %x, i32 0, i32 1431655764, i32 0 what was incorrect. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44936 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -8879,8 +8879,8 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
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if (!isa<PointerType>(X->getType())) {
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// Not interesting. Source pointer must be a cast from pointer.
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} else if (HasZeroPointerIndex) {
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// transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
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// into : GEP [10 x ubyte]* X, long 0, ...
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// transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ...
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// into : GEP [10 x i8]* X, i32 0, ...
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//
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// This occurs when the program declares an array extern like "int X[];"
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//
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@ -8900,8 +8900,8 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
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}
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} else if (GEP.getNumOperands() == 2) {
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// Transform things like:
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// %t = getelementptr ubyte* cast ([2 x int]* %str to uint*), uint %V
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// into: %t1 = getelementptr [2 x int*]* %str, int 0, uint %V; cast
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// %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V
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// into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast
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const Type *SrcElTy = cast<PointerType>(X->getType())->getElementType();
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const Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType();
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if (isa<ArrayType>(SrcElTy) &&
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@ -8917,12 +8917,11 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
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}
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// Transform things like:
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// getelementptr sbyte* cast ([100 x double]* X to sbyte*), int %tmp
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// getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp
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// (where tmp = 8*tmp2) into:
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// getelementptr [100 x double]* %arr, int 0, int %tmp.2
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// getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast
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if (isa<ArrayType>(SrcElTy) &&
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(ResElTy == Type::Int8Ty || ResElTy == Type::Int8Ty)) {
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if (isa<ArrayType>(SrcElTy) && ResElTy == Type::Int8Ty) {
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uint64_t ArrayEltSize =
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TD->getABITypeSize(cast<ArrayType>(SrcElTy)->getElementType());
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@ -8951,14 +8950,16 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
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}
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// If the index will be to exactly the right offset with the scale taken
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// out, perform the transformation.
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if (Scale && Scale->getZExtValue() % ArrayEltSize == 0) {
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if (isa<ConstantInt>(Scale))
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// out, perform the transformation. Note, we don't know whether Scale is
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// signed or not. We'll use unsigned version of division/modulo
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// operation after making sure Scale doesn't have the sign bit set.
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if (Scale && Scale->getSExtValue() >= 0LL &&
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Scale->getZExtValue() % ArrayEltSize == 0) {
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Scale = ConstantInt::get(Scale->getType(),
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Scale->getZExtValue() / ArrayEltSize);
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if (Scale->getZExtValue() != 1) {
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Constant *C = ConstantExpr::getIntegerCast(Scale, NewIdx->getType(),
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true /*SExt*/);
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false /*ZExt*/);
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Instruction *Sc = BinaryOperator::createMul(NewIdx, C, "idxscale");
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NewIdx = InsertNewInstBefore(Sc, GEP);
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}
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10
test/Transforms/InstCombine/2007-12-12-GEPScale.ll
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10
test/Transforms/InstCombine/2007-12-12-GEPScale.ll
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@ -0,0 +1,10 @@
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; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep 1431655764
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target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
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define i8* @foo([100 x {i8,i8,i8}]* %x) {
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entry:
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%p = bitcast [100 x {i8,i8,i8}]* %x to i8*
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%q = getelementptr i8* %p, i32 -4
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ret i8* %q
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}
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