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Truncate GEP indexes larger than the pointer size down to pointer size

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when doing this transform if the GEP is not inbounds.  No testcase because
it is very difficult to trigger this: instcombine already canonicalizes
GEP indices to pointer size, so it relies specific permutations of the
instcombine worklist.

Thanks to Duncan for pointing this possible problem out.

llvm-svn: 92495
This commit is contained in:
Chris Lattner 2010-01-04 18:57:15 +00:00
parent 8304a93ff4
commit 3b060b2d41
2 changed files with 18 additions and 9 deletions
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9
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -197,6 +197,9 @@ static void ComputeUnsignedMinMaxValuesFromKnownBits(const APInt &KnownZero,
Instruction *InstCombiner::
FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
CmpInst &ICI, ConstantInt *AndCst) {
// We need TD information to know the pointer size unless this is inbounds.
if (!GEP->isInBounds() && TD == 0) return 0;
ConstantArray *Init = dyn_cast<ConstantArray>(GV->getInitializer());
if (Init == 0 || Init->getNumOperands() > 1024) return 0;
@ -354,6 +357,12 @@ FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
// order the state machines in complexity of the generated code.
Value *Idx = GEP->getOperand(2);
// If the index is larger than the pointer size of the target, truncate the
// index down like the GEP would do implicitly. We don't have to do this for
// an inbounds GEP because the index can't be out of range.
if (!GEP->isInBounds() &&
Idx->getType()->getPrimitiveSizeInBits() > TD->getPointerSizeInBits())
Idx = Builder->CreateTrunc(Idx, TD->getIntPtrType(Idx->getContext()));
// If the comparison is only true for one or two elements, emit direct
// comparisons.

18
test/Transforms/InstCombine/load-cmp.ll
View File

@ -6,7 +6,7 @@
[double -10.0, double 1.0, double 4.0, double 2.0, double -20.0, double -40.0]
define i1 @test1(i32 %X) {
%P = getelementptr [10 x i16]* @G16, i32 0, i32 %X
%P = getelementptr inbounds [10 x i16]* @G16, i32 0, i32 %X
%Q = load i16* %P
%R = icmp eq i16 %Q, 0
ret i1 %R
@ -16,7 +16,7 @@ define i1 @test1(i32 %X) {
}
define i1 @test2(i32 %X) {
%P = getelementptr [10 x i16]* @G16, i32 0, i32 %X
%P = getelementptr inbounds [10 x i16]* @G16, i32 0, i32 %X
%Q = load i16* %P
%R = icmp slt i16 %Q, 85
ret i1 %R
@ -26,7 +26,7 @@ define i1 @test2(i32 %X) {
}
define i1 @test3(i32 %X) {
%P = getelementptr [6 x double]* @GD, i32 0, i32 %X
%P = getelementptr inbounds [6 x double]* @GD, i32 0, i32 %X
%Q = load double* %P
%R = fcmp oeq double %Q, 1.0
ret i1 %R
@ -36,7 +36,7 @@ define i1 @test3(i32 %X) {
}
define i1 @test4(i32 %X) {
%P = getelementptr [10 x i16]* @G16, i32 0, i32 %X
%P = getelementptr inbounds [10 x i16]* @G16, i32 0, i32 %X
%Q = load i16* %P
%R = icmp sle i16 %Q, 73
ret i1 %R
@ -48,7 +48,7 @@ define i1 @test4(i32 %X) {
}
define i1 @test5(i32 %X) {
%P = getelementptr [10 x i16]* @G16, i32 0, i32 %X
%P = getelementptr inbounds [10 x i16]* @G16, i32 0, i32 %X
%Q = load i16* %P
%R = icmp eq i16 %Q, 69
ret i1 %R
@ -60,7 +60,7 @@ define i1 @test5(i32 %X) {
}
define i1 @test6(i32 %X) {
%P = getelementptr [6 x double]* @GD, i32 0, i32 %X
%P = getelementptr inbounds [6 x double]* @GD, i32 0, i32 %X
%Q = load double* %P
%R = fcmp ogt double %Q, 0.0
ret i1 %R
@ -71,7 +71,7 @@ define i1 @test6(i32 %X) {
}
define i1 @test7(i32 %X) {
%P = getelementptr [6 x double]* @GD, i32 0, i32 %X
%P = getelementptr inbounds [6 x double]* @GD, i32 0, i32 %X
%Q = load double* %P
%R = fcmp olt double %Q, 0.0
ret i1 %R
@ -82,7 +82,7 @@ define i1 @test7(i32 %X) {
}
define i1 @test8(i32 %X) {
%P = getelementptr [10 x i16]* @G16, i32 0, i32 %X
%P = getelementptr inbounds [10 x i16]* @G16, i32 0, i32 %X
%Q = load i16* %P
%R = and i16 %Q, 3
%S = icmp eq i16 %R, 0
@ -101,7 +101,7 @@ define i1 @test8(i32 %X) {
]
define i1 @test9(i32 %X) {
%P = getelementptr [4 x { i32, i32 } ]* @GA, i32 0, i32 %X, i32 1
%P = getelementptr inbounds [4 x { i32, i32 } ]* @GA, i32 0, i32 %X, i32 1
%Q = load i32* %P
%R = icmp eq i32 %Q, 1
ret i1 %R