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[SCEV] createNodeForSelectOrPHIInstWithICmpInstCond(): generalize eq handling

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The current logic was: https://alive2.llvm.org/ce/z/j8muXk
but in reality the offset to the Y in the 'true' hand
does not need to exist: https://alive2.llvm.org/ce/z/MNQ7DZ
https://alive2.llvm.org/ce/z/S2pMQD

To catch that, instead of computing the Y's in both
hands and checking their equality, compute Y and C,
and check that C is 0 or 1.
This commit is contained in:
Roman Lebedev 2022-02-11 15:48:36 +03:00
parent a473c457f6
commit 4d0c0e6cc2
No known key found for this signature in database
GPG Key ID: 083C3EBB4A1689E0
4 changed files with 13 additions and 21 deletions
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19
llvm/lib/Analysis/ScalarEvolution.cpp
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@ -5952,21 +5952,20 @@ const SCEV *ScalarEvolution::createNodeForSelectOrPHIInstWithICmpInstCond(
}
break;
case ICmpInst::ICMP_NE:
// n != 0 ? n+x : 1+x -> n == 0 ? 1+x : n+x
// x != 0 ? x+y : C+y -> x == 0 ? C+y : x+y
std::swap(TrueVal, FalseVal);
LLVM_FALLTHROUGH;
case ICmpInst::ICMP_EQ:
// n == 0 ? 1+x : n+x -> umax(n, 1)+x
// x == 0 ? C+y : x+y -> umax(x, C)+y iff C u<= 1
if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
const SCEV *One = getOne(I->getType());
const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
const SCEV *LA = getSCEV(TrueVal);
const SCEV *RA = getSCEV(FalseVal);
const SCEV *LDiff = getMinusSCEV(LA, One);
const SCEV *RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(One, LS), LDiff);
const SCEV *X = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
const SCEV *TrueValExpr = getSCEV(TrueVal); // C+y
const SCEV *FalseValExpr = getSCEV(FalseVal); // x+y
const SCEV *Y = getMinusSCEV(FalseValExpr, X); // y = (x+y)-x
const SCEV *C = getMinusSCEV(TrueValExpr, Y); // C = (C+y)-y
if (isa<SCEVConstant>(C) && cast<SCEVConstant>(C)->getAPInt().ule(1))
return getAddExpr(getUMaxExpr(X, C), Y);
}
break;
default:

4
llvm/test/Analysis/ScalarEvolution/logical-operations.ll
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@ -478,7 +478,7 @@ define i32 @umin_seq_x_y_tautological(i32 %x, i32 %y) {
; CHECK-NEXT: %umin = call i32 @llvm.umin.i32(i32 %y, i32 %x)
; CHECK-NEXT: --> (%x umin %y) U: full-set S: full-set
; CHECK-NEXT: %r = select i1 %umin.is.zero, i32 0, i32 %umin
; CHECK-NEXT: --> %r U: full-set S: full-set
; CHECK-NEXT: --> (%x umin %y) U: full-set S: full-set
; CHECK-NEXT: Determining loop execution counts for: @umin_seq_x_y_tautological
;
%umin = call i32 @llvm.umin(i32 %y, i32 %x)
@ -492,7 +492,7 @@ define i32 @umin_seq_x_y_tautological_wrongtype(i32 %x, i32 %y) {
; CHECK-NEXT: %umax = call i32 @llvm.umax.i32(i32 %y, i32 %x)
; CHECK-NEXT: --> (%x umax %y) U: full-set S: full-set
; CHECK-NEXT: %r = select i1 %umax.is.zero, i32 0, i32 %umax
; CHECK-NEXT: --> %r U: full-set S: full-set
; CHECK-NEXT: --> (%x umax %y) U: full-set S: full-set
; CHECK-NEXT: Determining loop execution counts for: @umin_seq_x_y_tautological_wrongtype
;
%umax = call i32 @llvm.umax(i32 %y, i32 %x)

2
llvm/test/Analysis/ScalarEvolution/min-max-exprs.ll
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@ -127,7 +127,7 @@ define i8 @umax_basic_eq_off0(i8 %x, i8 %y) {
; CHECK-NEXT: %rhs = add i8 %x, %y
; CHECK-NEXT: --> (%x + %y) U: full-set S: full-set
; CHECK-NEXT: %r = select i1 %x.is.zero, i8 %lhs, i8 %rhs
; CHECK-NEXT: --> %r U: full-set S: full-set
; CHECK-NEXT: --> (%x + %y) U: full-set S: full-set
; CHECK-NEXT: Determining loop execution counts for: @umax_basic_eq_off0
;
%x.is.zero = icmp eq i8 %x, 0

9
polly/test/ForwardOpTree/changed-kind.ll
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@ -43,12 +43,5 @@ lor.end93:
; CHECK: Statistics {
; CHECK: Reloads: 1
; CHECK: }
; CHECK: After statements {
; CHECK: Stmt_lor_end93
; CHECK-NEXT: ReadAccess := [Reduction Type: NONE] [Scalar: 1]
; CHECK-NEXT: { Stmt_lor_end93[] -> MemRef3[] };
; CHECK-NEXT: new: { Stmt_lor_end93[] -> MemRef_c[0] };
; CHECK: Reloads: 0
; CHECK: }