[llvm] r364246 - [InstCombine] squash is-not-power-of-2 using ctpop
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Mon Jun 24 15:35:26 PDT 2019
Author: spatel
Date: Mon Jun 24 15:35:26 2019
New Revision: 364246
URL: http://llvm.org/viewvc/llvm-project?rev=364246&view=rev
Log:
[InstCombine] squash is-not-power-of-2 using ctpop
This is the Demorgan'd 'not' of the pattern handled in:
D63660 / rL364153
This is another intermediate IR step towards solving PR42314:
https://bugs.llvm.org/show_bug.cgi?id=42314
We can test if a value is not a power-of-2 using ctpop(X) > 1,
so combining that with an is-zero check of the input is the
same as testing if not exactly 1 bit is set:
(X == 0) || (ctpop(X) u> 1) --> ctpop(X) != 1
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
llvm/trunk/test/Transforms/InstCombine/ispow2.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=364246&r1=364245&r2=364246&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Mon Jun 24 15:35:26 2019
@@ -1022,22 +1022,32 @@ static Value *foldSignedTruncationCheck(
}
/// Reduce a pair of compares that check if a value has exactly 1 bit set.
-static Value *foldIsPowerOf2(ICmpInst *Cmp0, ICmpInst *Cmp1,
+static Value *foldIsPowerOf2(ICmpInst *Cmp0, ICmpInst *Cmp1, bool JoinedByAnd,
InstCombiner::BuilderTy &Builder) {
- // Handle 'and' commutation: make the not-equal compare the first operand.
- if (Cmp1->getPredicate() == ICmpInst::ICMP_NE)
+ // Handle 'and' / 'or' commutation: make the equality check the first operand.
+ if (JoinedByAnd && Cmp1->getPredicate() == ICmpInst::ICMP_NE)
+ std::swap(Cmp0, Cmp1);
+ else if (!JoinedByAnd && Cmp1->getPredicate() == ICmpInst::ICMP_EQ)
std::swap(Cmp0, Cmp1);
// (X != 0) && (ctpop(X) u< 2) --> ctpop(X) == 1
CmpInst::Predicate Pred0, Pred1;
Value *X;
- if (match(Cmp0, m_ICmp(Pred0, m_Value(X), m_ZeroInt())) &&
+ if (JoinedByAnd && match(Cmp0, m_ICmp(Pred0, m_Value(X), m_ZeroInt())) &&
match(Cmp1, m_ICmp(Pred1, m_Intrinsic<Intrinsic::ctpop>(m_Specific(X)),
m_SpecificInt(2))) &&
Pred0 == ICmpInst::ICMP_NE && Pred1 == ICmpInst::ICMP_ULT) {
Value *CtPop = Cmp1->getOperand(0);
return Builder.CreateICmpEQ(CtPop, ConstantInt::get(CtPop->getType(), 1));
}
+ // (X == 0) || (ctpop(X) u> 1) --> ctpop(X) != 1
+ if (!JoinedByAnd && match(Cmp0, m_ICmp(Pred0, m_Value(X), m_ZeroInt())) &&
+ match(Cmp1, m_ICmp(Pred1, m_Intrinsic<Intrinsic::ctpop>(m_Specific(X)),
+ m_SpecificInt(1))) &&
+ Pred0 == ICmpInst::ICMP_EQ && Pred1 == ICmpInst::ICMP_UGT) {
+ Value *CtPop = Cmp1->getOperand(0);
+ return Builder.CreateICmpNE(CtPop, ConstantInt::get(CtPop->getType(), 1));
+ }
return nullptr;
}
@@ -1083,7 +1093,7 @@ Value *InstCombiner::foldAndOfICmps(ICmp
if (Value *V = foldSignedTruncationCheck(LHS, RHS, CxtI, Builder))
return V;
- if (Value *V = foldIsPowerOf2(LHS, RHS, Builder))
+ if (Value *V = foldIsPowerOf2(LHS, RHS, true /* JoinedByAnd */, Builder))
return V;
// This only handles icmp of constants: (icmp1 A, C1) & (icmp2 B, C2).
@@ -2169,6 +2179,9 @@ Value *InstCombiner::foldOrOfICmps(ICmpI
if (Value *V = foldAndOrOfEqualityCmpsWithConstants(LHS, RHS, false, Builder))
return V;
+ if (Value *V = foldIsPowerOf2(LHS, RHS, false /* JoinedByAnd */, Builder))
+ return V;
+
// This only handles icmp of constants: (icmp1 A, C1) | (icmp2 B, C2).
if (!LHSC || !RHSC)
return nullptr;
Modified: llvm/trunk/test/Transforms/InstCombine/ispow2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/ispow2.ll?rev=364246&r1=364245&r2=364246&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/ispow2.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/ispow2.ll Mon Jun 24 15:35:26 2019
@@ -312,10 +312,8 @@ define i1 @is_pow2_ctpop_wrong_pred2(i32
define i1 @isnot_pow2_ctpop(i32 %x) {
; CHECK-LABEL: @isnot_pow2_ctpop(
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range !0
-; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i32 [[T0]], 1
-; CHECK-NEXT: [[ISZERO:%.*]] = icmp eq i32 [[X]], 0
-; CHECK-NEXT: [[R:%.*]] = or i1 [[ISZERO]], [[CMP]]
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ne i32 [[T0]], 1
+; CHECK-NEXT: ret i1 [[TMP1]]
;
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
%cmp = icmp ugt i32 %t0, 1
@@ -333,8 +331,8 @@ define i1 @isnot_pow2_ctpop_extra_uses(i
; CHECK-NEXT: call void @use_i1(i1 [[CMP]])
; CHECK-NEXT: [[ISZERO:%.*]] = icmp eq i32 [[X]], 0
; CHECK-NEXT: call void @use_i1(i1 [[ISZERO]])
-; CHECK-NEXT: [[R:%.*]] = or i1 [[ISZERO]], [[CMP]]
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ne i32 [[T0]], 1
+; CHECK-NEXT: ret i1 [[TMP1]]
;
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
%cmp = icmp ugt i32 %t0, 1
@@ -350,10 +348,8 @@ define i1 @isnot_pow2_ctpop_extra_uses(i
define <2 x i1> @isnot_pow2_ctpop_commute_vec(<2 x i8> %x) {
; CHECK-LABEL: @isnot_pow2_ctpop_commute_vec(
; CHECK-NEXT: [[T0:%.*]] = tail call <2 x i8> @llvm.ctpop.v2i8(<2 x i8> [[X:%.*]])
-; CHECK-NEXT: [[CMP:%.*]] = icmp ugt <2 x i8> [[T0]], <i8 1, i8 1>
-; CHECK-NEXT: [[ISZERO:%.*]] = icmp eq <2 x i8> [[X]], zeroinitializer
-; CHECK-NEXT: [[R:%.*]] = or <2 x i1> [[CMP]], [[ISZERO]]
-; CHECK-NEXT: ret <2 x i1> [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ne <2 x i8> [[T0]], <i8 1, i8 1>
+; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%t0 = tail call <2 x i8> @llvm.ctpop.v2i8(<2 x i8> %x)
%cmp = icmp ugt <2 x i8> %t0, <i8 1, i8 1>
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