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Constant-fold GEP-of-GEP into a single GEP.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98178 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-03-10 19:31:51 +00:00
parent a77338476f
commit 0891d752a6
2 changed files with 42 additions and 0 deletions
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11
lib/Analysis/ConstantFolding.cpp
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@ -589,6 +589,17 @@ static Constant *SymbolicallyEvaluateGEP(Constant *const *Ops, unsigned NumOps,
APInt Offset = APInt(BitWidth,
TD->getIndexedOffset(Ptr->getType(),
(Value**)Ops+1, NumOps-1));
// If this is a GEP of a GEP, fold it all into a single GEP.
while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
SmallVector<Value *, 4> NestedOps(GEP->op_begin()+1, GEP->op_end());
Ptr = cast<Constant>(GEP->getOperand(0));
Offset += APInt(BitWidth,
TD->getIndexedOffset(Ptr->getType(),
(Value**)NestedOps.data(),
NestedOps.size()));
}
// If the base value for this address is a literal integer value, fold the
// getelementptr to the resulting integer value casted to the pointer type.
if (BaseIsInt) {

31
test/Other/constant-fold-gep.ll
View File

@ -21,10 +21,12 @@
; PLAIN: %1 = type { double, float, double, double }
; PLAIN: %2 = type { i1, i1* }
; PLAIN: %3 = type { i64, i64 }
; PLAIN: %4 = type { i32, i32 }
; OPT: %0 = type { i1, double }
; OPT: %1 = type { double, float, double, double }
; OPT: %2 = type { i1, i1* }
; OPT: %3 = type { i64, i64 }
; OPT: %4 = type { i32, i32 }
; The automatic constant folder in opt does not have targetdata access, so
; it can't fold gep arithmetic, in general. However, the constant folder run
@ -122,6 +124,16 @@
@N = constant i64* getelementptr ({ i64, i64 }* null, i32 0, i32 1)
@O = constant i64* getelementptr ([2 x i64]* null, i32 0, i32 1)
; Fold GEP of a GEP. Theoretically some of these cases could be folded
; without using targetdata, however that's not implemented yet.
; PLAIN: @Z = global i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1)
; OPT: @Z = global i32* getelementptr (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1)
; TO: @Z = global i32* getelementptr inbounds ([3 x %0]* @ext, i64 0, i64 1, i32 1)
@ext = external global [3 x { i32, i32 }]
@Z = global i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x { i32, i32 }]* @ext, i64 0, i64 1, i32 0), i64 1)
; Duplicate all of the above as function return values rather than
; global initializers.
@ -468,3 +480,22 @@ define i64* @fO() nounwind {
%t = bitcast i64* getelementptr ([2 x i64]* null, i32 0, i32 1) to i64*
ret i64* %t
}
; PLAIN: define i32* @fZ() nounwind {
; PLAIN: %t = bitcast i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1) to i32*
; PLAIN: ret i32* %t
; PLAIN: }
; OPT: define i32* @fZ() nounwind {
; OPT: ret i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1)
; OPT: }
; TO: define i32* @fZ() nounwind {
; TO: ret i32* getelementptr inbounds ([3 x %0]* @ext, i64 0, i64 1, i32 1)
; TO: }
; SCEV: Classifying expressions for: @fZ
; SCEV: %t = bitcast i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x %4]* @ext, i64 0, i64 1, i32 0), i64 1) to i32*
; SCEV: --> ((3 * sizeof(i32)) + @ext)
define i32* @fZ() nounwind {
%t = bitcast i32* getelementptr inbounds (i32* getelementptr inbounds ([3 x { i32, i32 }]* @ext, i64 0, i64 1, i32 0), i64 1) to i32*
ret i32* %t
}