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[InstCombine] Fold x s> x & (-1 >> y) to x s> (-1 >> y)

Browse Source 
https://bugs.llvm.org/show_bug.cgi?id=38123
https://rise4fun.com/Alive/I3O

This pattern is not commutative!
We must make sure not to fold the commuted version!

llvm-svn: 337105
This commit is contained in:
Roman Lebedev 2018-07-14 20:08:16 +00:00
parent 9534e054cb
commit c5cf4d7783
2 changed files with 20 additions and 20 deletions
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6
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -2912,6 +2912,12 @@ static Value *foldICmpWithLowBitMaskedVal(ICmpInst &I,
assert(X == I.getOperand(0) && "instsimplify took care of commut. variant");
DstPred = ICmpInst::Predicate::ICMP_ULE;
break;
case ICmpInst::Predicate::ICMP_SGT:
// x s> x & (-1 >> y) -> x s> (-1 >> y)
if (X != I.getOperand(0)) // X must be on LHS of comparison!
return nullptr; // Ignore the other case.
DstPred = ICmpInst::Predicate::ICMP_SGT;
break;
// TODO: more folds are possible, https://bugs.llvm.org/show_bug.cgi?id=38123
default:
return nullptr;

34
test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll
View File

@ -22,9 +22,8 @@ declare <3 x i8> @gen3x8()
define i1 @p0() {
; CHECK-LABEL: @p0(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X]], 3
; CHECK-NEXT: [[RET:%.*]] = icmp sgt i8 [[X]], [[TMP0]]
; CHECK-NEXT: ret i1 [[RET]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i8 [[X]], 3
; CHECK-NEXT: ret i1 [[TMP1]]
;
%x = call i8 @gen8()
%tmp0 = and i8 %x, 3
@ -36,9 +35,8 @@ define i1 @pv(i8 %y) {
; CHECK-LABEL: @pv(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[TMP0]], [[X]]
; CHECK-NEXT: [[RET:%.*]] = icmp sgt i8 [[X]], [[TMP1]]
; CHECK-NEXT: ret i1 [[RET]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i8 [[X]], [[TMP0]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
@ -54,9 +52,8 @@ define i1 @pv(i8 %y) {
define <2 x i1> @p1_vec_splat() {
; CHECK-LABEL: @p1_vec_splat(
; CHECK-NEXT: [[X:%.*]] = call <2 x i8> @gen2x8()
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X]], <i8 3, i8 3>
; CHECK-NEXT: [[RET:%.*]] = icmp sgt <2 x i8> [[X]], [[TMP0]]
; CHECK-NEXT: ret <2 x i1> [[RET]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <2 x i8> [[X]], <i8 3, i8 3>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%x = call <2 x i8> @gen2x8()
%tmp0 = and <2 x i8> %x, <i8 3, i8 3>
@ -67,9 +64,8 @@ define <2 x i1> @p1_vec_splat() {
define <2 x i1> @p2_vec_nonsplat() {
; CHECK-LABEL: @p2_vec_nonsplat(
; CHECK-NEXT: [[X:%.*]] = call <2 x i8> @gen2x8()
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X]], <i8 3, i8 15>
; CHECK-NEXT: [[RET:%.*]] = icmp sgt <2 x i8> [[X]], [[TMP0]]
; CHECK-NEXT: ret <2 x i1> [[RET]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <2 x i8> [[X]], <i8 3, i8 15>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%x = call <2 x i8> @gen2x8()
%tmp0 = and <2 x i8> %x, <i8 3, i8 15> ; doesn't have to be splat.
@ -80,9 +76,8 @@ define <2 x i1> @p2_vec_nonsplat() {
define <3 x i1> @p3_vec_splat_undef() {
; CHECK-LABEL: @p3_vec_splat_undef(
; CHECK-NEXT: [[X:%.*]] = call <3 x i8> @gen3x8()
; CHECK-NEXT: [[TMP0:%.*]] = and <3 x i8> [[X]], <i8 3, i8 undef, i8 3>
; CHECK-NEXT: [[RET:%.*]] = icmp sgt <3 x i8> [[X]], [[TMP0]]
; CHECK-NEXT: ret <3 x i1> [[RET]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <3 x i8> [[X]], <i8 3, i8 undef, i8 3>
; CHECK-NEXT: ret <3 x i1> [[TMP1]]
;
%x = call <3 x i8> @gen3x8()
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
@ -101,8 +96,8 @@ define i1 @oneuse0() {
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X]], 3
; CHECK-NEXT: call void @use8(i8 [[TMP0]])
; CHECK-NEXT: [[RET:%.*]] = icmp sgt i8 [[X]], [[TMP0]]
; CHECK-NEXT: ret i1 [[RET]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i8 [[X]], 3
; CHECK-NEXT: ret i1 [[TMP1]]
;
%x = call i8 @gen8()
%tmp0 = and i8 %x, 3
@ -139,9 +134,8 @@ define i1 @cv0_GOOD(i8 %y) {
; CHECK-LABEL: @cv0_GOOD(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[TMP0]], [[X]]
; CHECK-NEXT: [[RET:%.*]] = icmp sgt i8 [[X]], [[TMP1]]
; CHECK-NEXT: ret i1 [[RET]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i8 [[X]], [[TMP0]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y