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[InstCombine] allow icmp (sub nsw) folds for vectors 

Also, clean up the code and comments for the existing folds in foldICmpSubConstant().

llvm-svn: 281631
This commit is contained in:
Sanjay Patel 2016-09-15 18:05:17 +00:00
parent 514068397e
commit 886a542e23
2 changed files with 41 additions and 50 deletions
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79
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -1420,30 +1420,6 @@ Instruction *InstCombiner::foldICmpWithConstant(ICmpInst &Cmp) {
if (!CI)
return nullptr;
// The following transforms are only worth it if the only user of the subtract
// is the icmp.
if (X->hasOneUse()) {
// (icmp sgt (sub nsw A B), -1) -> (icmp sge A, B)
if (Pred == ICmpInst::ICMP_SGT && CI->isAllOnesValue() &&
match(X, m_NSWSub(m_Value(A), m_Value(B))))
return new ICmpInst(ICmpInst::ICMP_SGE, A, B);
// (icmp sgt (sub nsw A B), 0) -> (icmp sgt A, B)
if (Pred == ICmpInst::ICMP_SGT && CI->isZero() &&
match(X, m_NSWSub(m_Value(A), m_Value(B))))
return new ICmpInst(ICmpInst::ICMP_SGT, A, B);
// (icmp slt (sub nsw A B), 0) -> (icmp slt A, B)
if (Pred == ICmpInst::ICMP_SLT && CI->isZero() &&
match(X, m_NSWSub(m_Value(A), m_Value(B))))
return new ICmpInst(ICmpInst::ICMP_SLT, A, B);
// (icmp slt (sub nsw A B), 1) -> (icmp sle A, B)
if (Pred == ICmpInst::ICMP_SLT && CI->isOne() &&
match(X, m_NSWSub(m_Value(A), m_Value(B))))
return new ICmpInst(ICmpInst::ICMP_SLE, A, B);
}
if (Cmp.isEquality()) {
ConstantInt *CI2;
if (match(X, m_AShr(m_ConstantInt(CI2), m_Value(A))) ||
@ -2306,27 +2282,46 @@ Instruction *InstCombiner::foldICmpDivConstant(ICmpInst &Cmp,
Instruction *InstCombiner::foldICmpSubConstant(ICmpInst &Cmp,
BinaryOperator *Sub,
const APInt *C) {
const APInt *C2;
if (!match(Sub->getOperand(0), m_APInt(C2)) || !Sub->hasOneUse())
Value *X = Sub->getOperand(0), *Y = Sub->getOperand(1);
ICmpInst::Predicate Pred = Cmp.getPredicate();
// The following transforms are only worth it if the only user of the subtract
// is the icmp.
if (!Sub->hasOneUse())
return nullptr;
// C-X <u C2 -> (X|(C2-1)) == C
// iff C & (C2-1) == C2-1
// C2 is a power of 2
if (Cmp.getPredicate() == ICmpInst::ICMP_ULT && C->isPowerOf2() &&
(*C2 & (*C - 1)) == (*C - 1))
return new ICmpInst(ICmpInst::ICMP_EQ,
Builder->CreateOr(Sub->getOperand(1), *C - 1),
Sub->getOperand(0));
if (Sub->hasNoSignedWrap()) {
// (icmp sgt (sub nsw X, Y), -1) -> (icmp sge X, Y)
if (Pred == ICmpInst::ICMP_SGT && C->isAllOnesValue())
return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
// C-X >u C2 -> (X|C2) != C
// iff C & C2 == C2
// C2+1 is a power of 2
if (Cmp.getPredicate() == ICmpInst::ICMP_UGT && (*C + 1).isPowerOf2() &&
(*C2 & *C) == *C)
return new ICmpInst(ICmpInst::ICMP_NE,
Builder->CreateOr(Sub->getOperand(1), *C),
Sub->getOperand(0));
// (icmp sgt (sub nsw X, Y), 0) -> (icmp sgt X, Y)
if (Pred == ICmpInst::ICMP_SGT && *C == 0)
return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
// (icmp slt (sub nsw X, Y), 0) -> (icmp slt X, Y)
if (Pred == ICmpInst::ICMP_SLT && *C == 0)
return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
// (icmp slt (sub nsw X, Y), 1) -> (icmp sle X, Y)
if (Pred == ICmpInst::ICMP_SLT && *C == 1)
return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
}
const APInt *C2;
if (!match(X, m_APInt(C2)))
return nullptr;
// C2 - Y <u C -> (Y | (C - 1)) == C2
// iff (C2 & (C - 1)) == C - 1 and C is a power of 2
if (Pred == ICmpInst::ICMP_ULT && C->isPowerOf2() &&
(*C2 & (*C - 1)) == (*C - 1))
return new ICmpInst(ICmpInst::ICMP_EQ, Builder->CreateOr(Y, *C - 1), X);
// C2 - Y >u C -> (Y | C) != C2
// iff C2 & C == C and C + 1 is a power of 2
if (Pred == ICmpInst::ICMP_UGT && (*C + 1).isPowerOf2() && (*C2 & *C) == *C)
return new ICmpInst(ICmpInst::ICMP_NE, Builder->CreateOr(Y, *C), X);
return nullptr;
}

12
llvm/test/Transforms/InstCombine/icmp.ll
View File

@ -2315,8 +2315,7 @@ define i1 @f1(i64 %a, i64 %b) {
define <2 x i1> @f1_vec(<2 x i64> %a, <2 x i64> %b) {
; CHECK-LABEL: @f1_vec(
; CHECK-NEXT: [[T:%.*]] = sub nsw <2 x i64> %a, %b
; CHECK-NEXT: [[V:%.*]] = icmp sgt <2 x i64> [[T]], <i64 -1, i64 -1>
; CHECK-NEXT: [[V:%.*]] = icmp sge <2 x i64> %a, %b
; CHECK-NEXT: ret <2 x i1> [[V]]
;
%t = sub nsw <2 x i64> %a, %b
@ -2336,8 +2335,7 @@ define i1 @f2(i64 %a, i64 %b) {
define <2 x i1> @f2_vec(<2 x i64> %a, <2 x i64> %b) {
; CHECK-LABEL: @f2_vec(
; CHECK-NEXT: [[T:%.*]] = sub nsw <2 x i64> %a, %b
; CHECK-NEXT: [[V:%.*]] = icmp sgt <2 x i64> [[T]], zeroinitializer
; CHECK-NEXT: [[V:%.*]] = icmp sgt <2 x i64> %a, %b
; CHECK-NEXT: ret <2 x i1> [[V]]
;
%t = sub nsw <2 x i64> %a, %b
@ -2357,8 +2355,7 @@ define i1 @f3(i64 %a, i64 %b) {
define <2 x i1> @f3_vec(<2 x i64> %a, <2 x i64> %b) {
; CHECK-LABEL: @f3_vec(
; CHECK-NEXT: [[T:%.*]] = sub nsw <2 x i64> %a, %b
; CHECK-NEXT: [[V:%.*]] = icmp slt <2 x i64> [[T]], zeroinitializer
; CHECK-NEXT: [[V:%.*]] = icmp slt <2 x i64> %a, %b
; CHECK-NEXT: ret <2 x i1> [[V]]
;
%t = sub nsw <2 x i64> %a, %b
@ -2378,8 +2375,7 @@ define i1 @f4(i64 %a, i64 %b) {
define <2 x i1> @f4_vec(<2 x i64> %a, <2 x i64> %b) {
; CHECK-LABEL: @f4_vec(
; CHECK-NEXT: [[T:%.*]] = sub nsw <2 x i64> %a, %b
; CHECK-NEXT: [[V:%.*]] = icmp slt <2 x i64> [[T]], <i64 1, i64 1>
; CHECK-NEXT: [[V:%.*]] = icmp sle <2 x i64> %a, %b
; CHECK-NEXT: ret <2 x i1> [[V]]
;
%t = sub nsw <2 x i64> %a, %b