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[InstCombine] KnownBits::isNonNegative should recognize b - a after a <= b (#145105)

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Alive2: https://alive2.llvm.org/ce/z/an9npN
Fixes #142283.
This commit is contained in:
Ross Kirsling 2025-06-24 09:51:49 -07:00 committed by GitHub
parent a84891698a
commit 7d2293d1d9
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2 changed files with 158 additions and 0 deletions
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5
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -362,6 +362,11 @@ static void computeKnownBitsAddSub(bool Add, const Value *Op0, const Value *Op1,
computeKnownBits(Op0, DemandedElts, Known2, Q, Depth + 1);
KnownOut = KnownBits::computeForAddSub(Add, NSW, NUW, Known2, KnownOut);
if (!Add && NSW && !KnownOut.isNonNegative() &&
isImpliedByDomCondition(ICmpInst::ICMP_SLE, Op1, Op0, Q.CxtI, Q.DL)
.value_or(false))
KnownOut.makeNonNegative();
}
static void computeKnownBitsMul(const Value *Op0, const Value *Op1, bool NSW,

153
llvm/test/Transforms/InstCombine/sub-after-sle-is-non-negative.ll Normal file
View File

@ -0,0 +1,153 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt < %s -passes=instcombine -S | FileCheck %s
declare void @subroutine(i16)
define void @test_as_arg(i8 %a, i8 %b) {
; CHECK-LABEL: define void @test_as_arg(
; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_END:.*]], label %[[COND_FALSE:.*]]
; CHECK: [[COND_FALSE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i8 [[B]], [[A]]
; CHECK-NEXT: [[CONV:%.*]] = zext nneg i8 [[SUB]] to i16
; CHECK-NEXT: call void @subroutine(i16 [[CONV]])
; CHECK-NEXT: br label %[[COND_END]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret void
;
%cmp = icmp sgt i8 %a, %b
br i1 %cmp, label %cond.end, label %cond.false
cond.false:
%sub = sub nsw i8 %b, %a
%conv = sext i8 %sub to i16
call void @subroutine(i16 %conv)
br label %cond.end
cond.end:
ret void
}
define i16 @test_as_retval(i8 %a, i8 %b) {
; CHECK-LABEL: define i16 @test_as_retval(
; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_FALSE:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: ret i16 0
; CHECK: [[COND_FALSE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i8 [[B]], [[A]]
; CHECK-NEXT: [[CONV:%.*]] = zext nneg i8 [[SUB]] to i16
; CHECK-NEXT: ret i16 [[CONV]]
;
%cmp = icmp sgt i8 %a, %b
br i1 %cmp, label %cond.true, label %cond.false
cond.true:
ret i16 0
cond.false:
%sub = sub nsw i8 %b, %a
%conv = sext i8 %sub to i16
ret i16 %conv
}
define void @test_as_arg_wrong_icmp(i8 %a, i8 %b) {
; CHECK-LABEL: define void @test_as_arg_wrong_icmp(
; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_END:.*]], label %[[COND_FALSE:.*]]
; CHECK: [[COND_FALSE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i8 [[B]], [[A]]
; CHECK-NEXT: [[CONV:%.*]] = sext i8 [[SUB]] to i16
; CHECK-NEXT: call void @subroutine(i16 [[CONV]])
; CHECK-NEXT: br label %[[COND_END]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret void
;
%cmp = icmp slt i8 %a, %b
br i1 %cmp, label %cond.end, label %cond.false
cond.false:
%sub = sub nsw i8 %b, %a
%conv = sext i8 %sub to i16
call void @subroutine(i16 %conv)
br label %cond.end
cond.end:
ret void
}
define void @test_as_arg_missing_nsw(i8 %a, i8 %b) {
; CHECK-LABEL: define void @test_as_arg_missing_nsw(
; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_END:.*]], label %[[COND_FALSE:.*]]
; CHECK: [[COND_FALSE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub i8 [[B]], [[A]]
; CHECK-NEXT: [[CONV:%.*]] = sext i8 [[SUB]] to i16
; CHECK-NEXT: call void @subroutine(i16 [[CONV]])
; CHECK-NEXT: br label %[[COND_END]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret void
;
%cmp = icmp sgt i8 %a, %b
br i1 %cmp, label %cond.end, label %cond.false
cond.false:
%sub = sub i8 %b, %a
%conv = sext i8 %sub to i16
call void @subroutine(i16 %conv)
br label %cond.end
cond.end:
ret void
}
define i16 @test_as_retval_wrong_icmp(i8 %a, i8 %b) {
; CHECK-LABEL: define i16 @test_as_retval_wrong_icmp(
; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_FALSE:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: ret i16 0
; CHECK: [[COND_FALSE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i8 [[B]], [[A]]
; CHECK-NEXT: [[CONV:%.*]] = sext i8 [[SUB]] to i16
; CHECK-NEXT: ret i16 [[CONV]]
;
%cmp = icmp slt i8 %a, %b
br i1 %cmp, label %cond.true, label %cond.false
cond.true:
ret i16 0
cond.false:
%sub = sub nsw i8 %b, %a
%conv = sext i8 %sub to i16
ret i16 %conv
}
define i16 @test_as_retval_missing_nsw(i8 %a, i8 %b) {
; CHECK-LABEL: define i16 @test_as_retval_missing_nsw(
; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_FALSE:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: ret i16 0
; CHECK: [[COND_FALSE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub i8 [[B]], [[A]]
; CHECK-NEXT: [[CONV:%.*]] = sext i8 [[SUB]] to i16
; CHECK-NEXT: ret i16 [[CONV]]
;
%cmp = icmp sgt i8 %a, %b
br i1 %cmp, label %cond.true, label %cond.false
cond.true:
ret i16 0
cond.false:
%sub = sub i8 %b, %a
%conv = sext i8 %sub to i16
ret i16 %conv
}