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[InstCombine] Simplify ctlz/cttz with bitreverse

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Summary: Fixes PR41273

Reviewers: spatel

Reviewed By: spatel

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60096

llvm-svn: 357521
This commit is contained in:
David Bolvansky 2019-04-02 20:13:28 +00:00
parent 13d8e92940
commit 5ba60b22a4
2 changed files with 21 additions and 19 deletions
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10
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
View File

@ -1324,12 +1324,20 @@ static Instruction *foldCttzCtlz(IntrinsicInst &II, InstCombiner &IC) {
assert((II.getIntrinsicID() == Intrinsic::cttz ||
II.getIntrinsicID() == Intrinsic::ctlz) &&
"Expected cttz or ctlz intrinsic");
bool IsTZ = II.getIntrinsicID() == Intrinsic::cttz;
Value *Op0 = II.getArgOperand(0);
Value *X;
// ctlz(bitreverse(x)) -> cttz(x)
// cttz(bitreverse(x)) -> ctlz(x)
if (match(Op0, m_BitReverse(m_Value(X)))) {
Intrinsic::ID ID = IsTZ ? Intrinsic::ctlz : Intrinsic::cttz;
Function *F = Intrinsic::getDeclaration(II.getModule(), ID, II.getType());
return CallInst::Create(F, {X, II.getArgOperand(1)});
}
KnownBits Known = IC.computeKnownBits(Op0, 0, &II);
// Create a mask for bits above (ctlz) or below (cttz) the first known one.
bool IsTZ = II.getIntrinsicID() == Intrinsic::cttz;
unsigned PossibleZeros = IsTZ ? Known.countMaxTrailingZeros()
: Known.countMaxLeadingZeros();
unsigned DefiniteZeros = IsTZ ? Known.countMinTrailingZeros()

30
llvm/test/Transforms/InstCombine/ctlz-cttz-bitreverse.ll
View File

@ -3,9 +3,8 @@
define i32 @ctlz_true_bitreverse(i32 %x) {
; CHECK-LABEL: @ctlz_true_bitreverse(
; CHECK-NEXT: [[A:%.*]] = tail call i32 @llvm.bitreverse.i32(i32 [[X:%.*]])
; CHECK-NEXT: [[B:%.*]] = tail call i32 @llvm.ctlz.i32(i32 [[A]], i1 true), !range !0
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @llvm.cttz.i32(i32 [[X:%.*]], i1 true), !range !0
; CHECK-NEXT: ret i32 [[TMP1]]
;
%a = tail call i32 @llvm.bitreverse.i32(i32 %x)
%b = tail call i32 @llvm.ctlz.i32(i32 %a, i1 true)
@ -14,9 +13,8 @@ define i32 @ctlz_true_bitreverse(i32 %x) {
define <2 x i64> @ctlz_true_bitreverse_vec(<2 x i64> %x) {
; CHECK-LABEL: @ctlz_true_bitreverse_vec(
; CHECK-NEXT: [[A:%.*]] = tail call <2 x i64> @llvm.bitreverse.v2i64(<2 x i64> [[X:%.*]])
; CHECK-NEXT: [[B:%.*]] = tail call <2 x i64> @llvm.ctlz.v2i64(<2 x i64> [[A]], i1 true)
; CHECK-NEXT: ret <2 x i64> [[B]]
; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i64> @llvm.cttz.v2i64(<2 x i64> [[X:%.*]], i1 true)
; CHECK-NEXT: ret <2 x i64> [[TMP1]]
;
%a = tail call <2 x i64> @llvm.bitreverse.v2i64(<2 x i64> %x)
%b = tail call <2 x i64> @llvm.ctlz.v2i64(<2 x i64> %a, i1 true)
@ -25,9 +23,8 @@ define <2 x i64> @ctlz_true_bitreverse_vec(<2 x i64> %x) {
define i32 @ctlz_false_bitreverse(i32 %x) {
; CHECK-LABEL: @ctlz_false_bitreverse(
; CHECK-NEXT: [[A:%.*]] = tail call i32 @llvm.bitreverse.i32(i32 [[X:%.*]])
; CHECK-NEXT: [[B:%.*]] = tail call i32 @llvm.ctlz.i32(i32 [[A]], i1 false), !range !0
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @llvm.cttz.i32(i32 [[X:%.*]], i1 false), !range !0
; CHECK-NEXT: ret i32 [[TMP1]]
;
%a = tail call i32 @llvm.bitreverse.i32(i32 %x)
%b = tail call i32 @llvm.ctlz.i32(i32 %a, i1 false)
@ -36,9 +33,8 @@ define i32 @ctlz_false_bitreverse(i32 %x) {
define i32 @cttz_true_bitreverse(i32 %x) {
; CHECK-LABEL: @cttz_true_bitreverse(
; CHECK-NEXT: [[A:%.*]] = tail call i32 @llvm.bitreverse.i32(i32 [[X:%.*]])
; CHECK-NEXT: [[B:%.*]] = tail call i32 @llvm.cttz.i32(i32 [[A]], i1 true), !range !0
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @llvm.ctlz.i32(i32 [[X:%.*]], i1 true), !range !0
; CHECK-NEXT: ret i32 [[TMP1]]
;
%a = tail call i32 @llvm.bitreverse.i32(i32 %x)
%b = tail call i32 @llvm.cttz.i32(i32 %a, i1 true)
@ -47,9 +43,8 @@ define i32 @cttz_true_bitreverse(i32 %x) {
define <2 x i64> @cttz_true_bitreverse_vec(<2 x i64> %x) {
; CHECK-LABEL: @cttz_true_bitreverse_vec(
; CHECK-NEXT: [[A:%.*]] = tail call <2 x i64> @llvm.bitreverse.v2i64(<2 x i64> [[X:%.*]])
; CHECK-NEXT: [[B:%.*]] = tail call <2 x i64> @llvm.cttz.v2i64(<2 x i64> [[A]], i1 true)
; CHECK-NEXT: ret <2 x i64> [[B]]
; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i64> @llvm.ctlz.v2i64(<2 x i64> [[X:%.*]], i1 true)
; CHECK-NEXT: ret <2 x i64> [[TMP1]]
;
%a = tail call <2 x i64> @llvm.bitreverse.v2i64(<2 x i64> %x)
%b = tail call <2 x i64> @llvm.cttz.v2i64(<2 x i64> %a, i1 true)
@ -58,9 +53,8 @@ define <2 x i64> @cttz_true_bitreverse_vec(<2 x i64> %x) {
define i32 @cttz_false_bitreverse(i32 %x) {
; CHECK-LABEL: @cttz_false_bitreverse(
; CHECK-NEXT: [[A:%.*]] = tail call i32 @llvm.bitreverse.i32(i32 [[X:%.*]])
; CHECK-NEXT: [[B:%.*]] = tail call i32 @llvm.cttz.i32(i32 [[A]], i1 false), !range !0
; CHECK-NEXT: ret i32 [[B]]
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @llvm.ctlz.i32(i32 [[X:%.*]], i1 false), !range !0
; CHECK-NEXT: ret i32 [[TMP1]]
;
%a = tail call i32 @llvm.bitreverse.i32(i32 %x)
%b = tail call i32 @llvm.cttz.i32(i32 %a, i1 false)