2ca8a3f213
This fixes a violation of the wrap flag rules introduced in c4048d8f. This was also noted in the (very old) PR23527. The issue being fixed is that we assume the inbound flag on any GEP assumes that all users of *any* gep (or add) which happens to map to that SCEV would also be UB if the (other) gep overflowed. That's simply not true. In terms of the test diffs, I don't see anything seriously problematic. The lost flags are expected (given the semantic restriction on when its legal to tag the SCEV), and there are several cases where the previously inferred flags are unsound per the new semantics. The only common trend I noticed when looking at the deltas is that by not considering branch on poison as immediate UB in ValueTracking, we do miss a few cases we could reclaim. We may be able to claw some of these back with the follow ideas mentioned in PR51817. It's worth noting that most of the changes are analysis result only changes. The two transform changes are pretty minimal. In one case, we miss the opportunity to infer a nuw (correctly). In the other, we fail to fold an exit and produce a loop invariant form instead. This one is probably over-reduced as the program appears to be undefined in practice, and neither before or after exploits that. Differential Revision: https://reviews.llvm.org/D109789
75 lines
4.0 KiB
LLVM
75 lines
4.0 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
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; RUN: opt < %s "-passes=print<scalar-evolution>" -disable-output 2>&1 | FileCheck %s
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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define dso_local void @_Z4loopi(i32 %width) local_unnamed_addr #0 {
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; CHECK-LABEL: '_Z4loopi'
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; CHECK-NEXT: Classifying expressions for: @_Z4loopi
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; CHECK-NEXT: %storage = alloca [2 x i32], align 4
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; CHECK-NEXT: --> %storage U: [0,-3) S: [-9223372036854775808,9223372036854775805)
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; CHECK-NEXT: %0 = bitcast [2 x i32]* %storage to i8*
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; CHECK-NEXT: --> %storage U: [0,-3) S: [-9223372036854775808,9223372036854775805)
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; CHECK-NEXT: %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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; CHECK-NEXT: --> {0,+,1}<nuw><nsw><%for.cond> U: [0,-2147483648) S: [0,-2147483648) Exits: %width LoopDispositions: { %for.cond: Computable }
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; CHECK-NEXT: %rem = sdiv i32 %i.0, 2
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; CHECK-NEXT: --> ({0,+,1}<nuw><nsw><%for.cond> /u 2) U: [0,1073741824) S: [0,1073741824) Exits: (%width /u 2) LoopDispositions: { %for.cond: Computable }
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; CHECK-NEXT: %idxprom = sext i32 %rem to i64
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; CHECK-NEXT: --> ({0,+,1}<nuw><nsw><%for.cond> /u 2) U: [0,2147483648) S: [0,2147483648) Exits: ((zext i32 %width to i64) /u 2) LoopDispositions: { %for.cond: Computable }
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; CHECK-NEXT: %arrayidx = getelementptr inbounds [2 x i32], [2 x i32]* %storage, i64 0, i64 %idxprom
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; CHECK-NEXT: --> ((4 * ({0,+,1}<nuw><nsw><%for.cond> /u 2))<nuw><nsw> + %storage) U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: ((4 * ((zext i32 %width to i64) /u 2))<nuw><nsw> + %storage) LoopDispositions: { %for.cond: Computable }
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; CHECK-NEXT: %1 = load i32, i32* %arrayidx, align 4
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; CHECK-NEXT: --> %1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
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; CHECK-NEXT: %call = call i32 @_Z3adji(i32 %1)
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; CHECK-NEXT: --> %call U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
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; CHECK-NEXT: %2 = load i32, i32* %arrayidx, align 4
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; CHECK-NEXT: --> %2 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
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; CHECK-NEXT: %add = add nsw i32 %2, %call
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; CHECK-NEXT: --> (%2 + %call) U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %for.cond: Variant }
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; CHECK-NEXT: %inc = add nsw i32 %i.0, 1
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; CHECK-NEXT: --> {1,+,1}<nuw><%for.cond> U: [1,0) S: [1,0) Exits: (1 + %width) LoopDispositions: { %for.cond: Computable }
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; CHECK-NEXT: Determining loop execution counts for: @_Z4loopi
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; CHECK-NEXT: Loop %for.cond: backedge-taken count is %width
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; CHECK-NEXT: Loop %for.cond: max backedge-taken count is -1
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; CHECK-NEXT: Loop %for.cond: Predicated backedge-taken count is %width
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; CHECK-NEXT: Predicates:
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; CHECK: Loop %for.cond: Trip multiple is 1
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;
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entry:
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%storage = alloca [2 x i32], align 4
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%0 = bitcast [2 x i32]* %storage to i8*
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call void @llvm.lifetime.start.p0i8(i64 8, i8* %0) #4
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call void @llvm.memset.p0i8.i64(i8* align 4 %0, i8 0, i64 8, i1 false)
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br label %for.cond
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for.cond:
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%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%cmp = icmp ne i32 %i.0, %width
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br i1 %cmp, label %for.body, label %for.cond.cleanup
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for.cond.cleanup:
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call void @llvm.lifetime.end.p0i8(i64 8, i8* %0) #4
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ret void
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for.body:
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%rem = sdiv i32 %i.0, 2
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%idxprom = sext i32 %rem to i64
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%arrayidx = getelementptr inbounds [2 x i32], [2 x i32]* %storage, i64 0, i64 %idxprom
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%1 = load i32, i32* %arrayidx, align 4
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%call = call i32 @_Z3adji(i32 %1)
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%2 = load i32, i32* %arrayidx, align 4
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%add = add nsw i32 %2, %call
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store i32 %add, i32* %arrayidx, align 4
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%inc = add nsw i32 %i.0, 1
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br label %for.cond
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}
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declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #1
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declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i1 immarg) #2
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declare dso_local i32 @_Z3adji(i32) local_unnamed_addr #3
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declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #1
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