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[ConstantRanges] Use APInt for constant case for urem/srem. 

Currently UREM & SREM on constant ranges produces overly pessimistic
results for single element constant ranges.

Delegate to APInt's implementation if both operands are single element
constant ranges. We already do something similar for other binary
operators, like binary AND.

Fixes PR49731.

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D105115
This commit is contained in:
Florian Hahn 2021-06-30 09:45:50 +01:00
parent ad8494c021
commit 611a02cce5
No known key found for this signature in database
GPG Key ID: 61D7554B5CECDC0D
2 changed files with 26 additions and 20 deletions
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18
llvm/lib/IR/ConstantRange.cpp
View File

@ -1221,6 +1221,15 @@ ConstantRange ConstantRange::urem(const ConstantRange &RHS) const {
if (isEmptySet() || RHS.isEmptySet() || RHS.getUnsignedMax().isNullValue())
return getEmpty();
if (const APInt *RHSInt = RHS.getSingleElement()) {
// UREM by null is UB.
if (RHSInt->isNullValue())
return getEmpty();
// Use APInt's implementation of UREM for single element ranges.
if (const APInt *LHSInt = getSingleElement())
return {LHSInt->urem(*RHSInt)};
}
// L % R for L < R is L.
if (getUnsignedMax().ult(RHS.getUnsignedMin()))
return *this;
@ -1234,6 +1243,15 @@ ConstantRange ConstantRange::srem(const ConstantRange &RHS) const {
if (isEmptySet() || RHS.isEmptySet())
return getEmpty();
if (const APInt *RHSInt = RHS.getSingleElement()) {
// SREM by null is UB.
if (RHSInt->isNullValue())
return getEmpty();
// Use APInt's implementation of SREM for single element ranges.
if (const APInt *LHSInt = getSingleElement())
return {LHSInt->srem(*RHSInt)};
}
ConstantRange AbsRHS = RHS.abs();
APInt MinAbsRHS = AbsRHS.getUnsignedMin();
APInt MaxAbsRHS = AbsRHS.getUnsignedMax();

28
llvm/test/Transforms/SCCP/binaryops-range-special-cases.ll
View File

@ -98,16 +98,10 @@ bb3:
define void @urem_cmp_constants() {
; CHECK-LABEL: @urem_cmp_constants(
; CHECK-NEXT: [[UREM_1:%.*]] = urem i16 12704, 12704
; CHECK-NEXT: [[C_1:%.*]] = icmp eq i16 [[UREM_1]], 0
; CHECK-NEXT: call void @use(i1 [[C_1]])
; CHECK-NEXT: [[C_2:%.*]] = icmp eq i16 [[UREM_1]], 1
; CHECK-NEXT: call void @use(i1 [[C_2]])
; CHECK-NEXT: [[UREM_2:%.*]] = urem i16 12704, 3
; CHECK-NEXT: [[C_3:%.*]] = icmp eq i16 [[UREM_2]], 2
; CHECK-NEXT: call void @use(i1 [[C_3]])
; CHECK-NEXT: [[C_4:%.*]] = icmp eq i16 [[UREM_2]], 1
; CHECK-NEXT: call void @use(i1 [[C_4]])
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[UREM_3:%.*]] = urem i16 12704, 0
; CHECK-NEXT: [[C_5:%.*]] = icmp eq i16 [[UREM_3]], 1
; CHECK-NEXT: call void @use(i1 [[C_5]])
@ -132,16 +126,10 @@ define void @urem_cmp_constants() {
define void @srem_cmp_constants() {
; CHECK-LABEL: @srem_cmp_constants(
; CHECK-NEXT: [[SREM_1:%.*]] = srem i16 12704, 12704
; CHECK-NEXT: [[C_1:%.*]] = icmp eq i16 [[SREM_1]], 0
; CHECK-NEXT: call void @use(i1 [[C_1]])
; CHECK-NEXT: [[C_2:%.*]] = icmp eq i16 [[SREM_1]], 1
; CHECK-NEXT: call void @use(i1 [[C_2]])
; CHECK-NEXT: [[SREM_2:%.*]] = srem i16 12704, 3
; CHECK-NEXT: [[C_3:%.*]] = icmp eq i16 [[SREM_2]], 2
; CHECK-NEXT: call void @use(i1 [[C_3]])
; CHECK-NEXT: [[C_4:%.*]] = icmp eq i16 [[SREM_2]], 1
; CHECK-NEXT: call void @use(i1 [[C_4]])
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[SREM_3:%.*]] = srem i16 12704, 0
; CHECK-NEXT: [[C_5:%.*]] = icmp eq i16 [[SREM_3]], 1
; CHECK-NEXT: call void @use(i1 [[C_5]])