wrongtest-intellif commented on code in PR #13724:
URL: https://github.com/apache/tvm/pull/13724#discussion_r1065295308
##########
src/tir/transforms/lower_intrin.cc:
##########
@@ -112,20 +113,33 @@ class IntrinInjecter : public
tvm::arith::IRMutatorWithAnalyzer {
// Common path, positive divisor
if (analyzer_->CanProveGreaterEqual(op->a, 0) ||
analyzer_->CanProveGreaterEqual(e, 0)) {
return truncdiv(op->a, op->b);
+ }
+
+ // If the numerator's lower bound is known, express the floordiv
+ // in terms of truncdiv using only positive operands.
+ arith::ConstIntBound const_int_bound = analyzer_->const_int_bound(op->a);
+ if (const_int_bound->min_value != arith::ConstIntBound::kNegInf &&
+ const_int_bound->min_value < 0 &&
+ const_int_bound->min_value > -(1LL << (op->a->dtype.bits() - 1))) {
Review Comment:
The meaning of bound `-(1LL << (op->a->dtype.bits() - 1)))` is sign free or
not? Could we use `min_value` interface of op.h here?
##########
src/tir/transforms/lower_intrin.cc:
##########
@@ -112,20 +113,33 @@ class IntrinInjecter : public
tvm::arith::IRMutatorWithAnalyzer {
// Common path, positive divisor
if (analyzer_->CanProveGreaterEqual(op->a, 0) ||
analyzer_->CanProveGreaterEqual(e, 0)) {
return truncdiv(op->a, op->b);
+ }
+
+ // If the numerator's lower bound is known, express the floordiv
+ // in terms of truncdiv using only positive operands.
+ arith::ConstIntBound const_int_bound = analyzer_->const_int_bound(op->a);
+ if (const_int_bound->min_value != arith::ConstIntBound::kNegInf &&
+ const_int_bound->min_value < 0 &&
+ const_int_bound->min_value > -(1LL << (op->a->dtype.bits() - 1))) {
+ IntImm min(op->a->dtype, const_int_bound->min_value);
+ PrimExpr ceildiv = truncdiv((op->b - 1) - min, op->b);
+ PrimExpr offset_numerator = analyzer_->Simplify(op->a + op->b *
ceildiv);
+ return truncdiv(offset_numerator, op->b) - ceildiv;
Review Comment:
IIUC, the rationale is:
```
a // b =>
(a + -min - -min) // b =>
(a + (x*b-y) - (x*b-y)) // b => ( where x is ceildiv(-min, b), x >= 0, y >=
0 )
(a + x*b) // b - x =>
(a + x*b) / b - x ( since a + x*b >= a + -min >= 0 )
```
Right?
##########
src/tir/transforms/lower_intrin.cc:
##########
@@ -165,21 +179,34 @@ class IntrinInjecter : public
tvm::arith::IRMutatorWithAnalyzer {
// Common pass, positive divisor
if (analyzer_->CanProveGreaterEqual(op->a, 0)) {
return truncmod(op->a, op->b);
+ }
+
+ // If the numerator's lower bound is known, express the floormod
+ // in terms of truncmod using only positive operands.
+ arith::ConstIntBound const_int_bound = analyzer_->const_int_bound(op->a);
+ if (const_int_bound->min_value != arith::ConstIntBound::kNegInf &&
+ const_int_bound->min_value < 0 &&
+ const_int_bound->min_value > -(1LL << (op->a->dtype.bits() - 1))) {
+ IntImm min(op->a->dtype, const_int_bound->min_value);
+ PrimExpr ceildiv = truncdiv(-min + (op->b - 1), op->b);
+ PrimExpr offset_numerator = analyzer_->Simplify(op->a + op->b *
ceildiv);
+ return truncmod(offset_numerator, op->b);
Review Comment:
```
floormod(a, b) =>
floormod(a + -min - -min, b) =>
floormod(a + (x*b-y) - (x*b-y)), b) => ( where x is ceildiv(-min, b), x >=
0, y >= 0 )
floormod(a + x*b, b) =>
(a + x*b) % b ( since a + x*b >= a + -min >= 0 )
```
Right?
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