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[InstCombine] allow icmp (shr/shl) folds for vectors

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These 2 helper functions were already using APInt internally, so just
change the API and caller to allow folds for splats. The scalar
regression tests look quite thorough, so I just added a couple of
tests to prove that vectors are handled too.

These folds should be grouped with the other cmp+shift folds though.
That can be an NFC follow-up.

llvm-svn: 281663
This commit is contained in:
Sanjay Patel 2016-09-15 21:35:30 +00:00
parent ffcefe6fd8
commit c6312b466a
4 changed files with 44 additions and 29 deletions
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49
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -1177,8 +1177,8 @@ Instruction *InstCombiner::foldICmpAddOpConst(Instruction &ICI,
/// (icmp eq/ne A, Log2(const2/const1)) ->
/// (icmp eq/ne A, Log2(const2) - Log2(const1)).
Instruction *InstCombiner::foldICmpCstShrConst(ICmpInst &I, Value *Op, Value *A,
ConstantInt *CI1,
ConstantInt *CI2) {
const APInt &AP1,
const APInt &AP2) {
assert(I.isEquality() && "Cannot fold icmp gt/lt");
auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
@ -1187,9 +1187,6 @@ Instruction *InstCombiner::foldICmpCstShrConst(ICmpInst &I, Value *Op, Value *A,
return new ICmpInst(Pred, LHS, RHS);
};
const APInt &AP1 = CI1->getValue();
const APInt &AP2 = CI2->getValue();
// Don't bother doing any work for cases which InstSimplify handles.
if (AP2 == 0)
return nullptr;
@ -1238,8 +1235,8 @@ Instruction *InstCombiner::foldICmpCstShrConst(ICmpInst &I, Value *Op, Value *A,
/// Handle "(icmp eq/ne (shl const2, A), const1)" ->
/// (icmp eq/ne A, TrailingZeros(const1) - TrailingZeros(const2)).
Instruction *InstCombiner::foldICmpCstShlConst(ICmpInst &I, Value *Op, Value *A,
ConstantInt *CI1,
ConstantInt *CI2) {
const APInt &AP1,
const APInt &AP2) {
assert(I.isEquality() && "Cannot fold icmp gt/lt");
auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
@ -1248,9 +1245,6 @@ Instruction *InstCombiner::foldICmpCstShlConst(ICmpInst &I, Value *Op, Value *A,
return new ICmpInst(Pred, LHS, RHS);
};
const APInt &AP1 = CI1->getValue();
const APInt &AP2 = CI2->getValue();
// Don't bother doing any work for cases which InstSimplify handles.
if (AP2 == 0)
return nullptr;
@ -1258,8 +1252,9 @@ Instruction *InstCombiner::foldICmpCstShlConst(ICmpInst &I, Value *Op, Value *A,
unsigned AP2TrailingZeros = AP2.countTrailingZeros();
if (!AP1 && AP2TrailingZeros != 0)
return getICmp(I.ICMP_UGE, A,
ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
return getICmp(
I.ICMP_UGE, A,
ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
if (AP1 == AP2)
return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
@ -1408,26 +1403,26 @@ Instruction *InstCombiner::foldICmpWithConstant(ICmpInst &Cmp) {
}
}
if (Cmp.isEquality()) {
const APInt *C2;
if (match(X, m_AShr(m_APInt(C2), m_Value(A))) ||
match(X, m_LShr(m_APInt(C2), m_Value(A)))) {
// (icmp eq/ne (ashr/lshr const2, A), const1)
if (Instruction *Inst = foldICmpCstShrConst(Cmp, X, A, *C, *C2))
return Inst;
}
if (match(X, m_Shl(m_APInt(C2), m_Value(A)))) {
// (icmp eq/ne (shl const2, A), const1)
if (Instruction *Inst = foldICmpCstShlConst(Cmp, X, A, *C, *C2))
return Inst;
}
}
// FIXME: Use m_APInt to allow folds for splat constants.
ConstantInt *CI = dyn_cast<ConstantInt>(Cmp.getOperand(1));
if (!CI)
return nullptr;
if (Cmp.isEquality()) {
ConstantInt *CI2;
if (match(X, m_AShr(m_ConstantInt(CI2), m_Value(A))) ||
match(X, m_LShr(m_ConstantInt(CI2), m_Value(A)))) {
// (icmp eq/ne (ashr/lshr const2, A), const1)
if (Instruction *Inst = foldICmpCstShrConst(Cmp, X, A, CI, CI2))
return Inst;
}
if (match(X, m_Shl(m_ConstantInt(CI2), m_Value(A)))) {
// (icmp eq/ne (shl const2, A), const1)
if (Instruction *Inst = foldICmpCstShlConst(Cmp, X, A, CI, CI2))
return Inst;
}
}
// Canonicalize icmp instructions based on dominating conditions.
BasicBlock *Parent = Cmp.getParent();
BasicBlock *Dom = Parent->getSinglePredecessor();

4
lib/Transforms/InstCombine/InstCombineInternal.h
View File

@ -549,9 +549,9 @@ private:
Instruction *foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
Constant *RHSC);
Instruction *foldICmpCstShrConst(ICmpInst &I, Value *Op, Value *A,
ConstantInt *CI1, ConstantInt *CI2);
const APInt &C1, const APInt &C2);
Instruction *foldICmpCstShlConst(ICmpInst &I, Value *Op, Value *A,
ConstantInt *CI1, ConstantInt *CI2);
const APInt &C1, const APInt &C2);
Instruction *foldICmpAddOpConst(Instruction &ICI, Value *X, ConstantInt *CI,
ICmpInst::Predicate Pred);
Instruction *foldICmpWithCastAndCast(ICmpInst &ICI);

10
test/Transforms/InstCombine/icmp-shr.ll
View File

@ -13,6 +13,16 @@ define i1 @lshr_eq_msb_low_last_zero(i8 %a) {
ret i1 %cmp
}
define <2 x i1> @lshr_eq_msb_low_last_zero_vec(<2 x i8> %a) {
; CHECK-LABEL: @lshr_eq_msb_low_last_zero_vec(
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt <2 x i8> %a, <i8 6, i8 6>
; CHECK-NEXT: ret <2 x i1> [[CMP]]
;
%shr = lshr <2 x i8> <i8 127, i8 127>, %a
%cmp = icmp eq <2 x i8> %shr, zeroinitializer
ret <2 x i1> %cmp
}
define i1 @ashr_eq_msb_low_second_zero(i8 %a) {
; CHECK-LABEL: @ashr_eq_msb_low_second_zero(
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 %a, 6

10
test/Transforms/InstCombine/icmp.ll
View File

@ -2194,6 +2194,16 @@ define i1 @shl_ap1_zero_ap2_non_zero_2(i32 %a) {
ret i1 %cmp
}
define <2 x i1> @shl_ap1_zero_ap2_non_zero_2_vec(<2 x i32> %a) {
; CHECK-LABEL: @shl_ap1_zero_ap2_non_zero_2_vec(
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt <2 x i32> %a, <i32 29, i32 29>
; CHECK-NEXT: ret <2 x i1> [[CMP]]
;
%shl = shl <2 x i32> <i32 4, i32 4>, %a
%cmp = icmp eq <2 x i32> %shl, zeroinitializer
ret <2 x i1> %cmp
}
define i1 @shl_ap1_zero_ap2_non_zero_4(i32 %a) {
; CHECK-LABEL: @shl_ap1_zero_ap2_non_zero_4(
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i32 %a, 30