[llvm] 553f8e7 - [InstCombine] simplify `icmp pred x, ~x` (#73990)
via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 6 07:43:30 PST 2025
Author: hanbeom
Date: 2025-02-06T23:43:26+08:00
New Revision: 553f8e71dd87ad7675e9edaeffdb9619b63a7cf9
URL: https://github.com/llvm/llvm-project/commit/553f8e71dd87ad7675e9edaeffdb9619b63a7cf9
DIFF: https://github.com/llvm/llvm-project/commit/553f8e71dd87ad7675e9edaeffdb9619b63a7cf9.diff
LOG: [InstCombine] simplify `icmp pred x, ~x` (#73990)
simplify compare between specific variable `X` and `NOT(X)`
Proof: https://alive2.llvm.org/ce/z/KTCpjP
Fixed https://github.com/llvm/llvm-project/issues/57532.
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/test/Transforms/InstCombine/icmp-of-xor-x.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 83534059bfb69a0..0feb6160b68fbb8 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -5065,6 +5065,27 @@ static Instruction *foldICmpXorXX(ICmpInst &I, const SimplifyQuery &Q,
if (PredOut != Pred && isKnownNonZero(A, Q))
return new ICmpInst(PredOut, Op0, Op1);
+ // These transform work when A is negative.
+ // X s< X^A, X s<= X^A, X u> X^A, X u>= X^A --> X s< 0
+ // X s> X^A, X s>= X^A, X u< X^A, X u<= X^A --> X s>= 0
+ if (match(A, m_Negative())) {
+ CmpInst::Predicate NewPred;
+ switch (ICmpInst::getStrictPredicate(Pred)) {
+ default:
+ return nullptr;
+ case ICmpInst::ICMP_SLT:
+ case ICmpInst::ICMP_UGT:
+ NewPred = ICmpInst::ICMP_SLT;
+ break;
+ case ICmpInst::ICMP_SGT:
+ case ICmpInst::ICMP_ULT:
+ NewPred = ICmpInst::ICMP_SGE;
+ break;
+ }
+ Constant *Const = Constant::getNullValue(Op0->getType());
+ return new ICmpInst(NewPred, Op0, Const);
+ }
+
return nullptr;
}
diff --git a/llvm/test/Transforms/InstCombine/icmp-of-xor-x.ll b/llvm/test/Transforms/InstCombine/icmp-of-xor-x.ll
index 0635bb31c44fcfb..8daef09719f75b9 100644
--- a/llvm/test/Transforms/InstCombine/icmp-of-xor-x.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-of-xor-x.ll
@@ -5,6 +5,349 @@ declare void @llvm.assume(i1)
declare void @barrier()
declare void @use.i8(i8)
+; Test case of X comp X^Neg_C, which have Transform to SLT.
+; X s< X^Neg_C --> X s< 0
+define i1 @src_slt(i8 %x) {
+; CHECK-LABEL: @src_slt(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %not = xor i8 %x, -1
+ %cmp = icmp slt i8 %x, %not
+ ret i1 %cmp
+}
+
+define <2 x i1> @src_slt_vec(<2 x i8> %x) {
+; CHECK-LABEL: @src_slt_vec(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt <2 x i8> [[X:%.*]], zeroinitializer
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -1, i8 -1>
+ %cmp = icmp slt <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+; X s<= X^Neg_C --> X s< 0
+define i1 @src_sle(i8 %x) {
+; CHECK-LABEL: @src_sle(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %not = xor i8 %x, -1
+ %cmp = icmp sle i8 %x, %not
+ ret i1 %cmp
+}
+
+define <2 x i1> @src_sle_vec(<2 x i8> %x) {
+; CHECK-LABEL: @src_sle_vec(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt <2 x i8> [[X:%.*]], zeroinitializer
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -1, i8 -1>
+ %cmp = icmp sle <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+; X u> X^Neg_C --> X s< 0
+define i1 @src_ugt(i8 %x) {
+; CHECK-LABEL: @src_ugt(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %not = xor i8 %x, -1
+ %cmp = icmp ugt i8 %x, %not
+ ret i1 %cmp
+}
+
+define <2 x i1> @src_ugt_vec(<2 x i8> %x) {
+; CHECK-LABEL: @src_ugt_vec(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt <2 x i8> [[X:%.*]], zeroinitializer
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -1, i8 -1>
+ %cmp = icmp ugt <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+; X u>= X^Neg_C --> X s< 0
+define i1 @src_uge(i8 %x) {
+; CHECK-LABEL: @src_uge(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %not = xor i8 %x, -1
+ %cmp = icmp uge i8 %x, %not
+ ret i1 %cmp
+}
+
+define <2 x i1> @src_uge_vec(<2 x i8> %x) {
+; CHECK-LABEL: @src_uge_vec(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt <2 x i8> [[X:%.*]], zeroinitializer
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -1, i8 -1>
+ %cmp = icmp uge <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+define <2 x i1> @src_uge_vec_min(<2 x i8> %x) {
+; CHECK-LABEL: @src_uge_vec_min(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt <2 x i8> [[X:%.*]], zeroinitializer
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -128, i8 -128>
+ %cmp = icmp uge <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+define <2 x i1> @src_uge_vec_128(<2 x i128> %x) {
+; CHECK-LABEL: @src_uge_vec_128(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt <2 x i128> [[X:%.*]], zeroinitializer
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i128> %x, <i128 -170141183460469231731687303715884105728, i128 -170141183460469231731687303715884105728>
+ %cmp = icmp uge <2 x i128> %x, %not
+ ret <2 x i1> %cmp
+}
+
+; Test case of X comp X^Neg_C, which have Transform to SGT.
+; X s> X^Neg_C --> X s> -1
+define i1 @src_sgt(i8 %x) {
+; CHECK-LABEL: @src_sgt(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -1
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %not = xor i8 %x, -1
+ %cmp = icmp sgt i8 %x, %not
+ ret i1 %cmp
+}
+
+define <2 x i1> @src_sgt_vec(<2 x i8> %x) {
+; CHECK-LABEL: @src_sgt_vec(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -1, i8 -1>
+ %cmp = icmp sgt <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+; X s>= X^Neg_C --> X s> -1
+define i1 @src_sge(i8 %x) {
+; CHECK-LABEL: @src_sge(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -1
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %not = xor i8 %x, -1
+ %cmp = icmp sge i8 %x, %not
+ ret i1 %cmp
+}
+
+define <2 x i1> @src_sge_vec(<2 x i8> %x) {
+; CHECK-LABEL: @src_sge_vec(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -1, i8 -1>
+ %cmp = icmp sge <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+; X u< X^Neg_C --> X s> -1
+define i1 @src_ult(i8 %x) {
+; CHECK-LABEL: @src_ult(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -1
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %not = xor i8 %x, -1
+ %cmp = icmp ult i8 %x, %not
+ ret i1 %cmp
+}
+
+define <2 x i1> @src_ult_vec(<2 x i8> %x) {
+; CHECK-LABEL: @src_ult_vec(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -1, i8 -1>
+ %cmp = icmp ult <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+; X u<= X^Neg_C --> X s> -1
+define i1 @src_ule(i8 %x) {
+; CHECK-LABEL: @src_ule(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -1
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %not = xor i8 %x, -1
+ %cmp = icmp ule i8 %x, %not
+ ret i1 %cmp
+}
+
+define <2 x i1> @src_ule_vec(<2 x i8> %x) {
+; CHECK-LABEL: @src_ule_vec(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -1, i8 -1>
+ %cmp = icmp ule <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+define <2 x i1> @src_ule_vec_min(<2 x i8> %x) {
+; CHECK-LABEL: @src_ule_vec_min(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i8> %x, <i8 -128, i8 -128>
+ %cmp = icmp ule <2 x i8> %x, %not
+ ret <2 x i1> %cmp
+}
+
+define <2 x i1> @src_ule_vec_128(<2 x i128> %x) {
+; CHECK-LABEL: @src_ule_vec_128(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i128> [[X:%.*]], <i128 -1, i128 -1>
+; CHECK-NEXT: ret <2 x i1> [[CMP]]
+;
+ %not = xor <2 x i128> %x, <i128 -170141183460469231731687303715884105728, i128 -170141183460469231731687303715884105728>
+ %cmp = icmp ule <2 x i128> %x, %not
+ ret <2 x i1> %cmp
+}
+
+; X comp X^Neg_C tests. negative
+; X comp Y
+define i1 @src_sle_xny(i8 %x, i8 %y) {
+; CHECK-LABEL: @src_sle_xny(
+; CHECK-NEXT: [[Y_NOT:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[CMP:%.*]] = icmp sle i8 [[X:%.*]], [[Y_NOT]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %y.not = xor i8 %y, -1
+ %cmp = icmp sle i8 %x, %y.not
+ ret i1 %cmp
+}
+define i1 @src_sle_nyx(i8 %x, i8 %y) {
+; CHECK-LABEL: @src_sle_nyx(
+; CHECK-NEXT: [[Y_NOT:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[CMP:%.*]] = icmp sge i8 [[X:%.*]], [[Y_NOT]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %y.not = xor i8 %y, -1
+ %cmp = icmp sle i8 %y.not, %x
+ ret i1 %cmp
+}
+define i1 @src_sge_xny(i8 %x, i8 %y) {
+; CHECK-LABEL: @src_sge_xny(
+; CHECK-NEXT: [[Y_NOT:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[CMP:%.*]] = icmp sge i8 [[X:%.*]], [[Y_NOT]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %y.not = xor i8 %y, -1
+ %cmp = icmp sge i8 %x, %y.not
+ ret i1 %cmp
+}
+define i1 @src_sge_nyx(i8 %x, i8 %y) {
+; CHECK-LABEL: @src_sge_nyx(
+; CHECK-NEXT: [[Y_NOT:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[CMP:%.*]] = icmp sle i8 [[X:%.*]], [[Y_NOT]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %y.not = xor i8 %y, -1
+ %cmp = icmp sge i8 %y.not, %x
+ ret i1 %cmp
+}
+define i1 @src_ule_xny(i8 %x, i8 %y) {
+; CHECK-LABEL: @src_ule_xny(
+; CHECK-NEXT: [[Y_NOT:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[CMP:%.*]] = icmp ule i8 [[X:%.*]], [[Y_NOT]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %y.not = xor i8 %y, -1
+ %cmp = icmp ule i8 %x, %y.not
+ ret i1 %cmp
+}
+define i1 @src_ule_nyx(i8 %x, i8 %y) {
+; CHECK-LABEL: @src_ule_nyx(
+; CHECK-NEXT: [[Y_NOT:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[CMP:%.*]] = icmp uge i8 [[X:%.*]], [[Y_NOT]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %y.not = xor i8 %y, -1
+ %cmp = icmp ule i8 %y.not, %x
+ ret i1 %cmp
+}
+define i1 @src_uge_xny(i8 %x, i8 %y) {
+; CHECK-LABEL: @src_uge_xny(
+; CHECK-NEXT: [[Y_NOT:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[CMP:%.*]] = icmp uge i8 [[X:%.*]], [[Y_NOT]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %y.not = xor i8 %y, -1
+ %cmp = icmp uge i8 %x, %y.not
+ ret i1 %cmp
+}
+define i1 @src_uge_nyx(i8 %x, i8 %y) {
+; CHECK-LABEL: @src_uge_nyx(
+; CHECK-NEXT: [[Y_NOT:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[CMP:%.*]] = icmp ule i8 [[X:%.*]], [[Y_NOT]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %y.not = xor i8 %y, -1
+ %cmp = icmp uge i8 %y.not, %x
+ ret i1 %cmp
+}
+
+; X comp X^Neg_C tests. negative
+; (X+1) comp X^Neg_C
+define i1 @src_sle_incx_nx(i8 %x) {
+; CHECK-LABEL: @src_sle_incx_nx(
+; CHECK-NEXT: [[TMP1:%.*]] = sub i8 -2, [[X:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp sge i8 [[TMP1]], [[X]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %nx = xor i8 %x, -1
+ %inc.x = add i8 %x, 1
+ %cmp = icmp sle i8 %inc.x, %nx
+ ret i1 %cmp
+}
+; (X-1) comp X^Neg_C
+define i1 @src_sle_decx_nx(i8 %x) {
+; CHECK-LABEL: @src_sle_decx_nx(
+; CHECK-NEXT: [[TMP1:%.*]] = sub i8 0, [[X:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp sle i8 [[X]], [[TMP1]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %nx = xor i8 %x, -1
+ %dec.x = add i8 %x, -1
+ %cmp = icmp sle i8 %dec.x, %nx
+ ret i1 %cmp
+}
+; X comp (X+1)^Neg_C
+define i1 @src_sle_x_nincx(i8 %x) {
+; CHECK-LABEL: @src_sle_x_nincx(
+; CHECK-NEXT: [[NOT_INC_X:%.*]] = sub i8 -2, [[X:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp sle i8 [[X]], [[NOT_INC_X]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %inc.x = add i8 %x, 1
+ %not.inc.x = xor i8 %inc.x, -1
+ %cmp = icmp sle i8 %x, %not.inc.x
+ ret i1 %cmp
+}
+; X comp (X-1)^Neg_C
+define i1 @src_sle_x_ndecx(i8 %x) {
+; CHECK-LABEL: @src_sle_x_ndecx(
+; CHECK-NEXT: [[NOT_DEC_X:%.*]] = sub i8 0, [[X:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp sle i8 [[X]], [[NOT_DEC_X]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %dec.x = add i8 %x, -1
+ %not.dec.x = xor i8 %dec.x, -1
+ %cmp = icmp sle i8 %x, %not.dec.x
+ ret i1 %cmp
+}
+
; test for (~x ^ y) < ~z
define i1 @test_xor1(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_xor1(
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