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[Polly] Avoid __builtin_assume circular context reasoning (#189350)

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The conversion of SCEVs to isl::pw_aff may only be valid under
conditions that have to be confirmed via RTC. This also happens with
__builtin_assume. These user-added assumptions are then added to
ScopInfo::Context. However, the conclusion in ScopInfo::Context is then
also used to simplify ("gist") its own RTC preconditions in
ScopInfo::AssumedContext and ScopInfo::InvalidContext away.

Avoid by adding user assumptions with preconditions to
ScopInfo::DefinedBehaviourContext instead, which is not used to simplify
AssumedContext/InvalidContext.

Fixes #187922

Thanks @thapgua for the report
This commit is contained in:
Michael Kruse 2026-03-30 13:08:23 +02:00 committed by GitHub
parent e901b0295d
commit 7fb4f732f5
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4 changed files with 178 additions and 8 deletions
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4
polly/include/polly/ScopInfo.h
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@ -1767,7 +1767,9 @@ private:
/// Scop::Context on the other side is an overapproximation and does not
/// include all requirements, but is always defined. However, there is still
/// no guarantee that there is no undefined behavior in
/// DefinedBehaviorContext.
/// DefinedBehaviorContext. Moreover, AssumedContext and InvalidContext are
/// gist'd using Scop::Context, but here we can add assumptions that only hold
/// under RTC-checked conditions.
isl::set DefinedBehaviorContext;
/// The schedule of the SCoP

17
polly/lib/Analysis/ScopBuilder.cpp
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@ -1388,6 +1388,7 @@ void ScopBuilder::addUserAssumptions(
NewParams.insert(Param);
}
size_t NumAssumptions = RecordedAssumptions.size();
SmallVector<isl_set *, 2> ConditionSets;
auto *TI = InScop ? CI->getParent()->getTerminator() : nullptr;
BasicBlock *BB = InScop ? CI->getParent() : R.getEntry();
@ -1427,9 +1428,19 @@ void ScopBuilder::addUserAssumptions(
ORE.emit(OptimizationRemarkAnalysis(DEBUG_TYPE, "UserAssumption", CI)
<< "Use user assumption: "
<< stringFromIslObj(AssumptionCtx, "null"));
isl::set newContext =
scop->getContext().intersect(isl::manage(AssumptionCtx));
scop->setContext(newContext);
// scop->setContext is used to gist AssumedContext and InvalidContext. Both
// add RTCs, so using setContext would remove the RTC that would ensure the
// correctness of AssumptionCtx. Using DefinedBehaviorContext which does not
// gist the other contexts.
// TODO: Use recordAssumption() for adding context/assumptions
if (NumAssumptions == RecordedAssumptions.size()) {
isl::set newContext =
scop->getContext().intersect(isl::manage(AssumptionCtx));
scop->setContext(newContext);
} else {
scop->intersectDefinedBehavior(isl::manage(AssumptionCtx), AS_ASSUMPTION);
}
}
}

155
polly/test/ScopInfo/issue187922.ll Normal file
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@ -0,0 +1,155 @@
; RUN: opt %loadNPMPolly '-passes=polly-custom<scops>' -polly-print-scops -disable-output < %s 2>&1 | FileCheck %s
;
; https://github.com/llvm/llvm-project/issues/187922
;
; The assumption 'p_2_loaded_from_var_0 <= 91' only holds if not 'p_2_loaded_from_var_0 >= 128'. Translation: if (trunc i64 %1 to i8) does not truncate any 1 bits, then we know that %1 <= 91.
; 'p_2_loaded_from_var_0 >= 128' must be in Invalid Context so we generate a RTC for it.
; 'p_2_loaded_from_var_0 <= 91' can only be in DefinedBehaviorContext, but not in "Context:" because "Context:" is used to gist AssumedContext and InvalidContext which would remove the required RTC: because %1 <= 91, the check if %1 >= 128 must not be optimized away.
; CHECK: Context:
; CHECK-NEXT: [p_0_loaded_from_var_3, p_1, p_2_loaded_from_var_0, p_3_loaded_from_var_7] -> { : -2147483648 <= p_0_loaded_from_var_3 <= 2147483647 and -1 <= p_1 <= 0 and -9223372036854775808 <= p_2_loaded_from_var_0 <= 9223372036854775807 and 0 <= p_3_loaded_from_var_7 <= 1 }
; CHECK: Assumed Context:
; CHECK-NEXT: [p_0_loaded_from_var_3, p_1, p_2_loaded_from_var_0, p_3_loaded_from_var_7] -> { : }
; CHECK: Invalid Context:
; CHECK-NEXT: [p_0_loaded_from_var_3, p_1, p_2_loaded_from_var_0, p_3_loaded_from_var_7] -> { : p_2_loaded_from_var_0 <= -129 or p_2_loaded_from_var_0 >= 128 or (p_0_loaded_from_var_3 < 0 and p_2_loaded_from_var_0 >= 5490102402889819 - p_1) or (p_0_loaded_from_var_3 < 0 and p_2_loaded_from_var_0 <= 69) or (p_0_loaded_from_var_3 > 0 and p_2_loaded_from_var_0 >= 5490102402889819 - p_1) or (p_0_loaded_from_var_3 > 0 and p_2_loaded_from_var_0 <= 69) or (p_0_loaded_from_var_3 = 0 and p_3_loaded_from_var_7 = 1 and p_2_loaded_from_var_0 >= 5490102402889819 - p_1) or (p_0_loaded_from_var_3 = 0 and p_3_loaded_from_var_7 = 1 and p_2_loaded_from_var_0 <= 69) }
; CHECK: Defined Behavior Context:
; CHECK-NEXT: [p_0_loaded_from_var_3, p_1, p_2_loaded_from_var_0, p_3_loaded_from_var_7] -> { : -1 <= p_1 <= 0 and -128 <= p_2_loaded_from_var_0 <= 91 and ((0 < p_0_loaded_from_var_3 <= 2147483647 and p_2_loaded_from_var_0 >= 70 and 0 <= p_3_loaded_from_var_7 <= 1) or (p_0_loaded_from_var_3 >= -2147483648 and p_2_loaded_from_var_0 >= 70 and p_3_loaded_from_var_7 > p_0_loaded_from_var_3 and 0 <= p_3_loaded_from_var_7 <= 1) or (p_0_loaded_from_var_3 = 0 and p_3_loaded_from_var_7 = 0)) }
; CHECK: p0: %4
; CHECK: p1: ((true + %tobool32.not) umin_seq (true + %.not))
; CHECK: p2: %1
; CHECK: p3: %3
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
@var_0 = external dso_local local_unnamed_addr global i64, align 8
@var_3 = external dso_local local_unnamed_addr global i32, align 4
@var_4 = external dso_local local_unnamed_addr global i8, align 1
@var_7 = external dso_local local_unnamed_addr global i8, align 1
@var_15 = external dso_local local_unnamed_addr global i32, align 4
@var_17 = external dso_local local_unnamed_addr global i16, align 2
@arr_4 = external dso_local local_unnamed_addr global [20 x i16], align 16
@arr_11 = external dso_local local_unnamed_addr global [20 x [20 x [20 x i32]]], align 16
; Function Attrs: nofree norecurse nosync nounwind memory(readwrite, argmem: none, inaccessiblemem: write, target_mem: none) uwtable
define dso_local noundef i32 @func() local_unnamed_addr #0 {
entry:
%0 = load i32, ptr @var_15, align 4, !tbaa !4
%1 = load i64, ptr @var_0, align 8, !tbaa !8
%conv17 = trunc i64 %1 to i8
%conv18 = sext i8 %conv17 to i32
%sub19 = add nsw i32 %conv18, -70
%sext.mask = and i32 %sub19, 255
%cmp26 = icmp eq i32 %sext.mask, 20
tail call void @llvm.assume(i1 %cmp26)
%tobool32.not = icmp eq i32 %0, 0
%2 = load i16, ptr @var_17, align 2
%.not = icmp eq i16 %2, 0
%narrow188 = select i1 %tobool32.not, i1 true, i1 %.not
%cmp61 = icmp slt i8 %conv17, 92
tail call void @llvm.assume(i1 %cmp61)
%conv95194 = sext i1 %narrow188 to i32
%3 = load i8, ptr @var_7, align 1, !tbaa !10, !range !12, !noundef !13
%loadedv = zext nneg i8 %3 to i64
%sub104 = sub nsw i64 1, %1
%cond111 = tail call i64 @llvm.smax.i64(i64 %sub104, i64 %loadedv)
%tobool112.not = icmp eq i64 %cond111, 0
%4 = load i32, ptr @var_3, align 4
%5 = load i8, ptr @var_4, align 1
%conv115 = zext i8 %5 to i32
%cond117 = select i1 %tobool112.not, i32 %conv115, i32 %4
%conv121 = add i32 %cond117, 65325
%6 = and i32 %conv121, 65535
%7 = icmp samesign ult i32 %6, 3
%tobool136.not.us.not = icmp eq i8 %3, 0
br i1 %7, label %for.body.lr.ph.split.us, label %for.body
for.body.lr.ph.split.us: ; preds = %entry
%tobool128.not = icmp eq i32 %4, 0
br i1 %tobool128.not, label %for.body.lr.ph.split.us.split.us, label %for.body.us.preheader
for.body.us.preheader: ; preds = %for.body.lr.ph.split.us
%8 = sext i1 %narrow188 to i64
%sext = zext nneg i32 %sub19 to i64
br label %for.body.us
for.body.lr.ph.split.us.split.us: ; preds = %for.body.lr.ph.split.us
br i1 %tobool136.not.us.not, label %for.body.us.us, label %for.body.us.us.us.preheader
for.body.us.us.us.preheader: ; preds = %for.body.lr.ph.split.us.split.us
%9 = sext i1 %narrow188 to i64
%sext215 = zext nneg i32 %sub19 to i64
br label %for.body.us.us.us
for.body.us.us.us: ; preds = %for.body.us.us.us, %for.body.us.us.us.preheader
%indvars.iv213 = phi i64 [ %9, %for.body.us.us.us.preheader ], [ %indvars.iv.next214, %for.body.us.us.us ]
%arrayidx148.us.us.us = getelementptr inbounds [1600 x i8], ptr @arr_11, i64 %indvars.iv213
%arrayidx150.us.us.us = getelementptr inbounds [80 x i8], ptr %arrayidx148.us.us.us, i64 %indvars.iv213
store i32 0, ptr %arrayidx150.us.us.us, align 16, !tbaa !4
%indvars.iv.next214 = add nsw i64 %indvars.iv213, 3
%10 = icmp slt i64 %indvars.iv.next214, %sext215
br i1 %10, label %for.body.us.us.us, label %for.cond.cleanup
for.body.us.us: ; preds = %for.body.us.us, %for.body.lr.ph.split.us.split.us
%indvars.iv217 = phi i32 [ %indvars.iv.next218, %for.body.us.us ], [ %conv95194, %for.body.lr.ph.split.us.split.us ]
%indvars.iv.next218 = add nsw i32 %indvars.iv217, 3
%cmp99.us.us = icmp sgt i32 %sub19, %indvars.iv.next218
br i1 %cmp99.us.us, label %for.body.us.us, label %for.cond.cleanup
for.body.us: ; preds = %for.cond122.for.cond.cleanup126_crit_edge.split.us204, %for.body.us.preheader
%indvars.iv210 = phi i64 [ %8, %for.body.us.preheader ], [ %indvars.iv.next211, %for.cond122.for.cond.cleanup126_crit_edge.split.us204 ]
%arrayidx.us = getelementptr inbounds [2 x i8], ptr @arr_4, i64 %indvars.iv210
%11 = load i16, ptr %arrayidx.us, align 2, !tbaa !14
%tobool136.not.us200.not = icmp eq i16 %11, 0
br i1 %tobool136.not.us200.not, label %for.cond122.for.cond.cleanup126_crit_edge.split.us204, label %for.body127.lr.ph.split.split.us.us
for.cond122.for.cond.cleanup126_crit_edge.split.us204: ; preds = %for.body127.lr.ph.split.split.us.us, %for.body.us
%indvars.iv.next211 = add nsw i64 %indvars.iv210, 3
%12 = icmp slt i64 %indvars.iv.next211, %sext
br i1 %12, label %for.body.us, label %for.cond.cleanup
for.body127.lr.ph.split.split.us.us: ; preds = %for.body.us
%arrayidx148.us = getelementptr inbounds [1600 x i8], ptr @arr_11, i64 %indvars.iv210
%arrayidx150.us = getelementptr inbounds [80 x i8], ptr %arrayidx148.us, i64 %indvars.iv210
store i32 0, ptr %arrayidx150.us, align 16, !tbaa !4
br label %for.cond122.for.cond.cleanup126_crit_edge.split.us204
for.cond.cleanup: ; preds = %for.body, %for.cond122.for.cond.cleanup126_crit_edge.split.us204, %for.body.us.us, %for.body.us.us.us
ret i32 0
for.body: ; preds = %for.body, %entry
%indvars.iv = phi i32 [ %indvars.iv.next, %for.body ], [ %conv95194, %entry ]
%indvars.iv.next = add nsw i32 %indvars.iv, 3
%cmp99 = icmp sgt i32 %sub19, %indvars.iv.next
br i1 %cmp99, label %for.body, label %for.cond.cleanup
}
; Function Attrs: nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: write)
declare void @llvm.assume(i1 noundef) #1
; Function Attrs: nocallback nocreateundeforpoison nofree nosync nounwind speculatable willreturn memory(none)
declare i64 @llvm.smax.i64(i64, i64) #2
attributes #0 = { nofree norecurse nosync nounwind memory(readwrite, argmem: none, inaccessiblemem: write, target_mem: none) uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
attributes #1 = { nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: write) }
attributes #2 = { nocallback nocreateundeforpoison nofree nosync nounwind speculatable willreturn memory(none) }
!llvm.module.flags = !{!0, !1, !2}
!llvm.ident = !{!3}
!llvm.errno.tbaa = !{!4}
!0 = !{i32 8, !"PIC Level", i32 2}
!1 = !{i32 7, !"PIE Level", i32 2}
!2 = !{i32 7, !"uwtable", i32 2}
!3 = !{!"clang version 23.0.0git (/home/meinersbur/src/llvm/polly/_src/clang 458f1aae8d2da5bf786ba53ea200e94a918ff55a)"}
!4 = !{!5, !5, i64 0}
!5 = !{!"int", !6, i64 0}
!6 = !{!"omnipotent char", !7, i64 0}
!7 = !{!"Simple C/C++ TBAA"}
!8 = !{!9, !9, i64 0}
!9 = !{!"long long", !6, i64 0}
!10 = !{!11, !11, i64 0}
!11 = !{!"_Bool", !6, i64 0}
!12 = !{i8 0, i8 2}
!13 = !{}
!14 = !{!15, !15, i64 0}
!15 = !{!"short", !6, i64 0}

10
polly/test/ScopInfo/user_provided_assumptions.ll
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@ -3,17 +3,19 @@
;
; CHECK: remark: <unknown>:0:0: SCoP begins here.
; CHECK-NEXT: remark: <unknown>:0:0: Use user assumption: [M, N] -> { : N <= 2147483647 - M }
; CHECK-NEXT: remark: <unknown>:0:0: Use user assumption: [M, N] -> { : -2147483648 - M <= N <= 2147483647 - M }
; CHECK-NEXT: remark: <unknown>:0:0: Use user assumption: [M, N, Debug] -> { : Debug = 0 and 0 < M <= 100 and -2147483648 - M <= N <= 2147483647 - M }
; CHECK-NEXT: remark: <unknown>:0:0: Use user assumption: [M, N, Debug] -> { : Debug = 0 and 0 < M <= 100 and 0 < N <= 2147483647 - M }
; CHECK-NEXT: remark: <unknown>:0:0: Use user assumption: [N, M] -> { : M >= -2147483648 - N }
; CHECK-NEXT: remark: <unknown>:0:0: Use user assumption: [N, M, Debug] -> { : Debug = 0 and M > 0 and -2147483648 - N <= M <= 100 }
; CHECK-NEXT: remark: <unknown>:0:0: Use user assumption: [N, M, Debug] -> { : Debug = 0 and N > 0 and 0 < M <= 100 }
; CHECK-NEXT: remark: <unknown>:0:0: SCoP ends here.
; SCOP: Context:
; SCOP-NEXT: [N, M, Debug] -> { : Debug = 0 and N > 0 and 0 < M <= 2147483647 - N and M <= 100 }
; SCOP-NEXT: [N, M, Debug] -> { : Debug = 0 and 0 < N <= 2147483647 and 0 < M <= 100 }
; SCOP: Assumed Context:
; SCOP-NEXT: [N, M, Debug] -> { : }
; SCOP: Invalid Context:
; SCOP-NEXT: [N, M, Debug] -> { : false }
; SCOP: Defined Behavior Context:
; SCOP-NEXT: [N, M, Debug] -> { : Debug = 0 and N > 0 and 0 < M <= 2147483647 - N and M <= 100 }
;
; #include <stdio.h>
;