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[InstSimplify] Handle selects of GEPs with 0 offset

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In particular (since it wouldn't fit nicely in the summary):
(select (icmp eq V 0) P (getelementptr P V)) -> (getelementptr P V)

Differential Revision: https://reviews.llvm.org/D31435

llvm-svn: 301880
This commit is contained in:
George Burgess IV 2017-05-01 23:12:08 +00:00
parent a5a31d2cfd
commit 25e6d2b2ce
2 changed files with 32 additions and 0 deletions
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13
lib/Analysis/InstructionSimplify.cpp
View File

@ -62,6 +62,8 @@ static Value *SimplifyOrInst(Value *, Value *, const SimplifyQuery &, unsigned);
static Value *SimplifyXorInst(Value *, Value *, const SimplifyQuery &, unsigned);
static Value *SimplifyCastInst(unsigned, Value *, Type *,
const SimplifyQuery &, unsigned);
static Value *SimplifyGEPInst(Type *, ArrayRef<Value *>, const SimplifyQuery &,
unsigned);
/// For a boolean type or a vector of boolean type, return false or a vector
/// with every element false.
@ -3491,6 +3493,17 @@ static const Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
}
}
// Same for GEPs.
if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
if (MaxRecurse) {
SmallVector<Value *, 8> NewOps(GEP->getNumOperands());
transform(GEP->operands(), NewOps.begin(),
[&](Value *V) { return V == Op ? RepOp : V; });
return SimplifyGEPInst(GEP->getSourceElementType(), NewOps, Q,
MaxRecurse - 1);
}
}
// TODO: We could hand off more cases to instsimplify here.
// If all operands are constant after substituting Op for RepOp then we can

19
test/Transforms/InstSimplify/select.ll
View File

@ -431,3 +431,22 @@ define i8 @do_not_assume_sel_cond(i1 %cond, i8 %x, i8 %y) {
ret i8 %sel
}
define i32* @select_icmp_eq_0_gep_operand(i32* %base, i64 %n) {
; CHECK-LABEL: @select_icmp_eq_0_gep_operand(
; CHECK-NEXT: [[GEP:%.*]] = getelementptr
; CHECK-NEXT: ret i32* [[GEP]]
%cond = icmp eq i64 %n, 0
%gep = getelementptr i32, i32* %base, i64 %n
%r = select i1 %cond, i32* %base, i32* %gep
ret i32* %r
}
define i32* @select_icmp_ne_0_gep_operand(i32* %base, i64 %n) {
; CHECK-LABEL: @select_icmp_ne_0_gep_operand(
; CHECK-NEXT: [[GEP:%.*]] = getelementptr
; CHECK-NEXT: ret i32* [[GEP]]
%cond = icmp ne i64 %n, 0
%gep = getelementptr i32, i32* %base, i64 %n
%r = select i1 %cond, i32* %gep, i32* %base
ret i32* %r
}