maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[InstCombine] add folds for icmp (smin X, Y), X 

Min/max canonicalization (r287585) exposes the fact that we're missing combines for min/max patterns. 
This patch won't solve the example that was attached to that thread, so something else still needs fixing.

The line between InstCombine and InstSimplify gets blurry here because sometimes the icmp instruction that
we want to fold to already exists, but sometimes it's the swapped form of what we want.

Corresponding changes for smax/umin/umax to follow.

Differential Revision: https://reviews.llvm.org/D27531

llvm-svn: 289855
This commit is contained in:
Sanjay Patel 2016-12-15 19:13:37 +00:00
parent e793966d80
commit d640641a61
3 changed files with 59 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
llvm/include/llvm/IR/PatternMatch.h
View File

@ -1349,6 +1349,16 @@ m_c_Xor(const LHS &L, const RHS &R) {
return m_CombineOr(m_Xor(L, R), m_Xor(R, L));
}
// TODO: Add the related SMax, UMax, UMin commuted matchers.
/// Matches an SMin with LHS and RHS in either order.
template<typename LHS, typename RHS>
inline match_combine_or<MaxMin_match<ICmpInst, LHS, RHS, smin_pred_ty>,
MaxMin_match<ICmpInst, RHS, LHS, smin_pred_ty>>
m_c_SMin(const LHS &L, const RHS &R) {
return m_CombineOr(m_SMin(L, R), m_SMin(R, L));
}
} // end namespace PatternMatch
} // end namespace llvm

37
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -3030,6 +3030,40 @@ Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) {
return nullptr;
}
/// Fold icmp Pred smin(X, Y), X.
static Instruction *foldICmpWithSMin(ICmpInst &Cmp) {
ICmpInst::Predicate Pred = Cmp.getPredicate();
Value *Op0 = Cmp.getOperand(0);
Value *X = Cmp.getOperand(1);
// TODO: This should be expanded to handle smax/umax/umin.
// Canonicalize minimum operand to LHS of the icmp.
if (match(X, m_c_SMin(m_Specific(Op0), m_Value()))) {
std::swap(Op0, X);
Pred = Cmp.getSwappedPredicate();
}
Value *Y;
if (!match(Op0, m_c_SMin(m_Specific(X), m_Value(Y))))
return nullptr;
// smin(X, Y) == X --> X <= Y
// smin(X, Y) >= X --> X <= Y
if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE)
return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
// smin(X, Y) != X --> X > Y
// smin(X, Y) < X --> X > Y
if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT)
return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
// These cases should be handled in InstSimplify:
// smin(X, Y) <= X --> true
// smin(X, Y) > X --> false
return nullptr;
}
Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
if (!I.isEquality())
return nullptr;
@ -4277,6 +4311,9 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
if (Instruction *Res = foldICmpBinOp(I))
return Res;
if (Instruction *Res = foldICmpWithSMin(I))
return Res;
{
Value *A, *B;
// Transform (A & ~B) == 0 --> (A & B) != 0

48
llvm/test/Transforms/InstCombine/smin-icmp.ll
View File

@ -11,9 +11,7 @@
define i1 @eq_smin1(i32 %x, i32 %y) {
; CHECK-LABEL: @eq_smin1(
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %x, %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[SEL]], %x
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 %x, %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%cmp1 = icmp slt i32 %x, %y
@ -26,9 +24,7 @@ define i1 @eq_smin1(i32 %x, i32 %y) {
define i1 @eq_smin2(i32 %x, i32 %y) {
; CHECK-LABEL: @eq_smin2(
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %y, %x
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 %x
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[SEL]], %x
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 %x, %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%cmp1 = icmp slt i32 %y, %x
@ -42,9 +38,7 @@ define i1 @eq_smin2(i32 %x, i32 %y) {
define i1 @eq_smin3(i32 %a, i32 %y) {
; CHECK-LABEL: @eq_smin3(
; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[X]], %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[X]], [[SEL]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%x = add i32 %a, 3 ; thwart complexity-based canonicalization
@ -59,9 +53,7 @@ define i1 @eq_smin3(i32 %a, i32 %y) {
define i1 @eq_smin4(i32 %a, i32 %y) {
; CHECK-LABEL: @eq_smin4(
; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3
; CHECK-NEXT: [[CMP1:%.*]] = icmp sgt i32 [[X]], %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 [[X]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[X]], [[SEL]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%x = add i32 %a, 3 ; thwart complexity-based canonicalization
@ -75,9 +67,7 @@ define i1 @eq_smin4(i32 %a, i32 %y) {
define i1 @sge_smin1(i32 %x, i32 %y) {
; CHECK-LABEL: @sge_smin1(
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %x, %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y
; CHECK-NEXT: [[CMP2:%.*]] = icmp sge i32 [[SEL]], %x
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 %x, %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%cmp1 = icmp slt i32 %x, %y
@ -90,9 +80,7 @@ define i1 @sge_smin1(i32 %x, i32 %y) {
define i1 @sge_smin2(i32 %x, i32 %y) {
; CHECK-LABEL: @sge_smin2(
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %y, %x
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 %x
; CHECK-NEXT: [[CMP2:%.*]] = icmp sge i32 [[SEL]], %x
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 %x, %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%cmp1 = icmp slt i32 %y, %x
@ -106,9 +94,7 @@ define i1 @sge_smin2(i32 %x, i32 %y) {
define i1 @sge_smin3(i32 %a, i32 %y) {
; CHECK-LABEL: @sge_smin3(
; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[X]], %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], [[SEL]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%x = add i32 %a, 3 ; thwart complexity-based canonicalization
@ -123,9 +109,7 @@ define i1 @sge_smin3(i32 %a, i32 %y) {
define i1 @sge_smin4(i32 %a, i32 %y) {
; CHECK-LABEL: @sge_smin4(
; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3
; CHECK-NEXT: [[CMP1:%.*]] = icmp sgt i32 [[X]], %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %y, i32 [[X]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], [[SEL]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp sle i32 [[X]], %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%x = add i32 %a, 3 ; thwart complexity-based canonicalization
@ -139,9 +123,7 @@ define i1 @sge_smin4(i32 %a, i32 %y) {
define i1 @ne_smin1(i32 %x, i32 %y) {
; CHECK-LABEL: @ne_smin1(
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %x, %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y
; CHECK-NEXT: [[CMP2:%.*]] = icmp ne i32 [[SEL]], %x
; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 %x, %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%cmp1 = icmp slt i32 %x, %y
@ -168,9 +150,7 @@ define i1 @ne_smin2(i32 %x, i32 %y) {
define i1 @ne_smin3(i32 %a, i32 %y) {
; CHECK-LABEL: @ne_smin3(
; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[X]], %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y
; CHECK-NEXT: [[CMP2:%.*]] = icmp ne i32 [[X]], [[SEL]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%x = add i32 %a, 3 ; thwart complexity-based canonicalization
@ -199,9 +179,7 @@ define i1 @ne_smin4(i32 %a, i32 %y) {
define i1 @slt_smin1(i32 %x, i32 %y) {
; CHECK-LABEL: @slt_smin1(
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 %x, %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 %x, i32 %y
; CHECK-NEXT: [[CMP2:%.*]] = icmp slt i32 [[SEL]], %x
; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 %x, %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%cmp1 = icmp slt i32 %x, %y
@ -228,9 +206,7 @@ define i1 @slt_smin2(i32 %x, i32 %y) {
define i1 @slt_smin3(i32 %a, i32 %y) {
; CHECK-LABEL: @slt_smin3(
; CHECK-NEXT: [[X:%.*]] = add i32 %a, 3
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[X]], %y
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 [[X]], i32 %y
; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], [[SEL]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], %y
; CHECK-NEXT: ret i1 [[CMP2]]
;
%x = add i32 %a, 3 ; thwart complexity-based canonicalization