[llvm] 68b24c3 - [CVP] Simplify comparisons without constant operand
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Thu Nov 3 07:35:35 PDT 2022
Author: Nikita Popov
Date: 2022-11-03T15:35:27+01:00
New Revision: 68b24c3b448946f86586be6e66af64cdce6edadc
URL: https://github.com/llvm/llvm-project/commit/68b24c3b448946f86586be6e66af64cdce6edadc
DIFF: https://github.com/llvm/llvm-project/commit/68b24c3b448946f86586be6e66af64cdce6edadc.diff
LOG: [CVP] Simplify comparisons without constant operand
CVP currently only tries to simplify comparisons if there is a
constant operand. However, even if both are non-constant, we may
be able to determine the result of the comparison based on range
information.
IPSCCP is already capable of doing this, but because it runs very
early, it may miss some cases.
Differential Revision: https://reviews.llvm.org/D137253
Added:
Modified:
llvm/lib/Analysis/LazyValueInfo.cpp
llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
llvm/test/Transforms/CorrelatedValuePropagation/mul.ll
llvm/test/Transforms/CorrelatedValuePropagation/shl.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index 2fae260e0d8fe..6f61091a41b98 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -1859,9 +1859,27 @@ LazyValueInfo::Tristate LazyValueInfo::getPredicateAt(unsigned P, Value *LHS,
return getPredicateAt(CmpInst::getSwappedPredicate(Pred), RHS, C, CxtI,
UseBlockValue);
- // Got two non-Constant values. While we could handle them somewhat,
- // by getting their constant ranges, and applying ConstantRange::icmp(),
- // so far it did not appear to be profitable.
+ // Got two non-Constant values. Try to determine the comparison results based
+ // on the block values of the two operands, e.g. because they have
+ // non-overlapping ranges.
+ if (UseBlockValue) {
+ Module *M = CxtI->getModule();
+ ValueLatticeElement L =
+ getImpl(PImpl, AC, M).getValueInBlock(LHS, CxtI->getParent(), CxtI);
+ if (L.isOverdefined())
+ return LazyValueInfo::Unknown;
+
+ ValueLatticeElement R =
+ getImpl(PImpl, AC, M).getValueInBlock(RHS, CxtI->getParent(), CxtI);
+ Type *Ty = CmpInst::makeCmpResultType(LHS->getType());
+ if (Constant *Res = L.getCompare((CmpInst::Predicate)P, Ty, R,
+ M->getDataLayout())) {
+ if (Res->isNullValue())
+ return LazyValueInfo::False;
+ if (Res->isOneValue())
+ return LazyValueInfo::True;
+ }
+ }
return LazyValueInfo::Unknown;
}
diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index ad47fd7c6e9d1..ea887d982b1b7 100644
--- a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -340,18 +340,16 @@ static bool processICmp(ICmpInst *Cmp, LazyValueInfo *LVI) {
/// exploiting range information.
static bool constantFoldCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
Value *Op0 = Cmp->getOperand(0);
- auto *C = dyn_cast<Constant>(Cmp->getOperand(1));
- if (!C)
- return false;
-
+ Value *Op1 = Cmp->getOperand(1);
LazyValueInfo::Tristate Result =
- LVI->getPredicateAt(Cmp->getPredicate(), Op0, C, Cmp,
+ LVI->getPredicateAt(Cmp->getPredicate(), Op0, Op1, Cmp,
/*UseBlockValue=*/true);
if (Result == LazyValueInfo::Unknown)
return false;
++NumCmps;
- Constant *TorF = ConstantInt::get(Type::getInt1Ty(Cmp->getContext()), Result);
+ Constant *TorF =
+ ConstantInt::get(CmpInst::makeCmpResultType(Op0->getType()), Result);
Cmp->replaceAllUsesWith(TorF);
Cmp->eraseFromParent();
return true;
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
index 4a3d9c752f04e..506aac79358f6 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
@@ -1180,10 +1180,8 @@ define void @non_const_range(i32 %a, i32 %b) {
; CHECK-NEXT: br i1 [[AND]], label [[IF:%.*]], label [[ELSE:%.*]]
; CHECK: if:
; CHECK-NEXT: [[A_100:%.*]] = add nuw nsw i32 [[A]], 100
-; CHECK-NEXT: [[CMP3:%.*]] = icmp ne i32 [[A_100]], [[B]]
-; CHECK-NEXT: call void @check1(i1 [[CMP3]])
-; CHECK-NEXT: [[CMP4:%.*]] = icmp eq i32 [[A_100]], [[B]]
-; CHECK-NEXT: call void @check1(i1 [[CMP4]])
+; CHECK-NEXT: call void @check1(i1 true)
+; CHECK-NEXT: call void @check1(i1 false)
; CHECK-NEXT: [[A_10:%.*]] = add nuw nsw i32 [[A]], 10
; CHECK-NEXT: [[CMP5:%.*]] = icmp ne i32 [[A_10]], [[B]]
; CHECK-NEXT: call void @check1(i1 [[CMP5]])
@@ -1220,8 +1218,7 @@ define i1 @non_const_range_minmax(i8 %a, i8 %b) {
; CHECK-LABEL: @non_const_range_minmax(
; CHECK-NEXT: [[A2:%.*]] = call i8 @llvm.umin.i8(i8 [[A:%.*]], i8 10)
; CHECK-NEXT: [[B2:%.*]] = call i8 @llvm.umax.i8(i8 [[B:%.*]], i8 11)
-; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i8 [[A2]], [[B2]]
-; CHECK-NEXT: ret i1 [[CMP1]]
+; CHECK-NEXT: ret i1 true
;
%a2 = call i8 @llvm.umin.i8(i8 %a, i8 10)
%b2 = call i8 @llvm.umax.i8(i8 %b, i8 11)
@@ -1229,6 +1226,7 @@ define i1 @non_const_range_minmax(i8 %a, i8 %b) {
ret i1 %cmp1
}
+; FIXME: Also support vectors.
define <2 x i1> @non_const_range_minmax_vec(<2 x i8> %a, <2 x i8> %b) {
; CHECK-LABEL: @non_const_range_minmax_vec(
; CHECK-NEXT: [[A2:%.*]] = call <2 x i8> @llvm.umin.v2i8(<2 x i8> [[A:%.*]], <2 x i8> <i8 10, i8 10>)
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/mul.ll b/llvm/test/Transforms/CorrelatedValuePropagation/mul.ll
index 3ac26f4507099..c69d259984bd0 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/mul.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/mul.ll
@@ -209,8 +209,7 @@ define i1 @nsw_range1(i8 %b) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[C:%.*]] = add nuw nsw i8 [[B:%.*]], -3
; CHECK-NEXT: [[MUL:%.*]] = mul nsw i8 [[C]], 4
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[C]], [[MUL]]
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 false
;
entry:
%c = add nuw nsw i8 %b, -3
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/shl.ll b/llvm/test/Transforms/CorrelatedValuePropagation/shl.ll
index 98113cbdae36a..88311219dee58 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/shl.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/shl.ll
@@ -412,8 +412,7 @@ define i1 @nsw_range1(i8 %b) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[C:%.*]] = add nuw nsw i8 [[B:%.*]], -3
; CHECK-NEXT: [[SHL:%.*]] = shl nsw i8 [[C]], 2
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[C]], [[SHL]]
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 false
;
entry:
%c = add nuw nsw i8 %b, -3
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