[llvm] r364153 - [InstCombine] squash is-power-of-2 that uses ctpop
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Sun Jun 23 07:22:38 PDT 2019
Author: spatel
Date: Sun Jun 23 07:22:37 2019
New Revision: 364153
URL: http://llvm.org/viewvc/llvm-project?rev=364153&view=rev
Log:
[InstCombine] squash is-power-of-2 that uses ctpop
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 power-of-2-or-0 using ctpop(X) < 2,
so combining that with a non-zero check of the input is the
same as testing if exactly 1 bit is set:
(X != 0) && (ctpop(X) u< 2) --> ctpop(X) == 1
Differential Revision: https://reviews.llvm.org/D63660
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=364153&r1=364152&r2=364153&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Sun Jun 23 07:22:37 2019
@@ -1021,6 +1021,26 @@ static Value *foldSignedTruncationCheck(
CxtI.getName() + ".simplified");
}
+/// Reduce a pair of compares that check if a value has exactly 1 bit set.
+static Value *foldIsPowerOf2(ICmpInst *Cmp0, ICmpInst *Cmp1,
+ InstCombiner::BuilderTy &Builder) {
+ // Handle 'and' commutation: make the not-equal compare the first operand.
+ if (Cmp1->getPredicate() == ICmpInst::ICMP_NE)
+ 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())) &&
+ 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));
+ }
+ return nullptr;
+}
+
/// Fold (icmp)&(icmp) if possible.
Value *InstCombiner::foldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS,
Instruction &CxtI) {
@@ -1063,6 +1083,9 @@ Value *InstCombiner::foldAndOfICmps(ICmp
if (Value *V = foldSignedTruncationCheck(LHS, RHS, CxtI, Builder))
return V;
+ if (Value *V = foldIsPowerOf2(LHS, RHS, Builder))
+ return V;
+
// This only handles icmp of constants: (icmp1 A, C1) & (icmp2 B, C2).
Value *LHS0 = LHS->getOperand(0), *RHS0 = RHS->getOperand(0);
ConstantInt *LHSC = dyn_cast<ConstantInt>(LHS->getOperand(1));
Modified: llvm/trunk/test/Transforms/InstCombine/ispow2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/ispow2.ll?rev=364153&r1=364152&r2=364153&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/ispow2.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/ispow2.ll Sun Jun 23 07:22:37 2019
@@ -187,13 +187,13 @@ define i1 @is_pow2or0_negate_op_extra_us
declare i32 @llvm.ctpop.i32(i32)
declare <2 x i8> @llvm.ctpop.v2i8(<2 x i8>)
+; (X != 0) && (ctpop(X) u< 2) --> ctpop(X) == 1
+
define i1 @is_pow2_ctpop(i32 %x) {
; CHECK-LABEL: @is_pow2_ctpop(
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range !0
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[T0]], 2
-; CHECK-NEXT: [[NOTZERO:%.*]] = icmp ne i32 [[X]], 0
-; CHECK-NEXT: [[R:%.*]] = and i1 [[NOTZERO]], [[CMP]]
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i32 [[T0]], 1
+; CHECK-NEXT: ret i1 [[TMP1]]
;
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
%cmp = icmp ult i32 %t0, 2
@@ -212,8 +212,8 @@ define i1 @is_pow2_ctpop_extra_uses(i32
; CHECK-NEXT: call void @use_i1(i1 [[CMP]])
; CHECK-NEXT: [[NOTZERO:%.*]] = icmp ne i32 [[X]], 0
; CHECK-NEXT: call void @use_i1(i1 [[NOTZERO]])
-; CHECK-NEXT: [[R:%.*]] = and i1 [[NOTZERO]], [[CMP]]
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i32 [[T0]], 1
+; CHECK-NEXT: ret i1 [[TMP1]]
;
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
%cmp = icmp ult i32 %t0, 2
@@ -229,10 +229,8 @@ define i1 @is_pow2_ctpop_extra_uses(i32
define <2 x i1> @is_pow2_ctpop_commute_vec(<2 x i8> %x) {
; CHECK-LABEL: @is_pow2_ctpop_commute_vec(
; CHECK-NEXT: [[T0:%.*]] = tail call <2 x i8> @llvm.ctpop.v2i8(<2 x i8> [[X:%.*]])
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult <2 x i8> [[T0]], <i8 2, i8 2>
-; CHECK-NEXT: [[NOTZERO:%.*]] = icmp ne <2 x i8> [[X]], zeroinitializer
-; CHECK-NEXT: [[R:%.*]] = and <2 x i1> [[CMP]], [[NOTZERO]]
-; CHECK-NEXT: ret <2 x i1> [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq <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 ult <2 x i8> %t0, <i8 2, i8 2>
@@ -241,6 +239,8 @@ define <2 x i1> @is_pow2_ctpop_commute_v
ret <2 x i1> %r
}
+; Negative test - wrong constant.
+
define i1 @is_pow2_ctpop_wrong_cmp_op1(i32 %x) {
; CHECK-LABEL: @is_pow2_ctpop_wrong_cmp_op1(
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range !0
@@ -256,6 +256,8 @@ define i1 @is_pow2_ctpop_wrong_cmp_op1(i
ret i1 %r
}
+; Negative test - wrong constant.
+
define i1 @is_pow2_ctpop_wrong_cmp_op2(i32 %x) {
; CHECK-LABEL: @is_pow2_ctpop_wrong_cmp_op2(
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range !0
@@ -271,6 +273,8 @@ define i1 @is_pow2_ctpop_wrong_cmp_op2(i
ret i1 %r
}
+; Negative test - wrong predicate.
+
define i1 @is_pow2_ctpop_wrong_pred1(i32 %x) {
; CHECK-LABEL: @is_pow2_ctpop_wrong_pred1(
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range !0
@@ -286,6 +290,8 @@ define i1 @is_pow2_ctpop_wrong_pred1(i32
ret i1 %r
}
+; Negative test - wrong predicate.
+
define i1 @is_pow2_ctpop_wrong_pred2(i32 %x) {
; CHECK-LABEL: @is_pow2_ctpop_wrong_pred2(
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range !0
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