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[ScopDetect] Evaluate and verify branches at branch condition, not icmp
The validity of a branch condition must be verified at the location of the branch (the branch instruction), not the location of the icmp that is used in the branch instruction. When verifying at the wrong location, we may accept an icmp that is defined within a loop which itself dominates, but does not contain the branch instruction. Such loops cannot be modeled as we only introduce domain dimensions for surrounding loops. To address this problem we change the scop detection to evaluate and verify SCEV expressions at the right location. This issue has been around since at least r179148 "scop detection: properly instantiate SCEVs to the place where they are used", where we explicitly set the scope to the wrong location. Before this commit the scope was not explicitly set, which probably also resulted in the scope around the ICmp to be choosen. This resolves http://llvm.org/PR30989 Reported-by: Eli Friedman <efriedma@codeaurora.org> llvm-svn: 286769
This commit is contained in:
Tobias Grosser
parent
987dad2bc3
commit
a2f8fa33aa
@ -388,7 +388,7 @@ bool ScopDetection::isValidBranch(BasicBlock &BB, BranchInst *BI,
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isa<UndefValue>(ICmp->getOperand(1)))
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return invalid<ReportUndefOperand>(Context, /*Assert=*/true, &BB, ICmp);
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Loop *L = LI->getLoopFor(ICmp->getParent());
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Loop *L = LI->getLoopFor(&BB);
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const SCEV *LHS = SE->getSCEVAtScope(ICmp->getOperand(0), L);
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const SCEV *RHS = SE->getSCEVAtScope(ICmp->getOperand(1), L);
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@ -0,0 +1,47 @@
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; RUN: opt %loadPolly -polly-detect -analyze < %s | \
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; RUN: FileCheck %s -check-prefix=DETECT
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; RUN: opt %loadPolly -polly-scops -analyze < %s | \
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; RUN: FileCheck %s -check-prefix=SCOP
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; DETECT: Valid Region for Scop: loop => barrier
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; DETECT-NEXT: Valid Region for Scop: branch => end
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; SCOP: Statements {
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; SCOP-NEXT: Stmt_then
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; SCOP-NEXT: Domain :=
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; SCOP-NEXT: [p_0] -> { Stmt_then[] : p_0 <= -2 or p_0 >= 0 };
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; SCOP-NEXT: Schedule :=
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; SCOP-NEXT: [p_0] -> { Stmt_then[] -> [] };
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; SCOP-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 0]
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; SCOP-NEXT: [p_0] -> { Stmt_then[] -> MemRef_A[0] };
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; SCOP-NEXT: }
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target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
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target triple = "aarch64--linux-android"
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define void @f(i16 %event, float* %A) {
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entry:
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br label %loop
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loop:
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%indvar = phi i8 [ 0, %entry ], [ %indvar.next, %loop ]
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%indvar.next = add i8 %indvar, -1
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store float 1.0, float* %A
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%cmp = icmp eq i8 %indvar.next, 0
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br i1 false, label %barrier, label %loop
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barrier:
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fence seq_cst
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br label %branch
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branch:
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br i1 %cmp, label %branch, label %then
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then:
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store float 1.0, float* %A
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br label %end
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end:
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unreachable
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}
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@ -0,0 +1,83 @@
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; RUN: opt %loadPolly -polly-scops -analyze < %s | \
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; RUN: FileCheck %s -check-prefix=NONAFFINE
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; RUN: opt %loadPolly -polly-scops -analyze \
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; RUN: -polly-allow-nonaffine-branches=false < %s | \
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; RUN: FileCheck %s -check-prefix=NO-NONEAFFINE
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; NONAFFINE: Statements {
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; NONAFFINE-NEXT: Stmt_loop
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; NONAFFINE-NEXT: Domain :=
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; NONAFFINE-NEXT: [p] -> { Stmt_loop[0] : p = 100 };
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; NONAFFINE-NEXT: Schedule :=
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; NONAFFINE-NEXT: [p] -> { Stmt_loop[i0] -> [0, 0] };
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; NONAFFINE-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 0]
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; NONAFFINE-NEXT: [p] -> { Stmt_loop[i0] -> MemRef_A[0] };
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; NONAFFINE-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
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; NONAFFINE-NEXT: [p] -> { Stmt_loop[i0] -> MemRef_cmp[] };
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; NONAFFINE-NEXT: Stmt_branch__TO__end
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; NONAFFINE-NEXT: Domain :=
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; NONAFFINE-NEXT: [p] -> { Stmt_branch__TO__end[] : p = 100 };
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; NONAFFINE-NEXT: Schedule :=
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; NONAFFINE-NEXT: [p] -> { Stmt_branch__TO__end[] -> [1, 0] };
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; NONAFFINE-NEXT: ReadAccess := [Reduction Type: NONE] [Scalar: 1]
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; NONAFFINE-NEXT: [p] -> { Stmt_branch__TO__end[] -> MemRef_cmp[] };
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; NONAFFINE-NEXT: MayWriteAccess := [Reduction Type: NONE] [Scalar: 0]
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; NONAFFINE-NEXT: [p] -> { Stmt_branch__TO__end[] -> MemRef_A[0] };
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; NONAFFINE-NEXT: }
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; NO-NONEAFFINE: Statements {
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; NO-NONEAFFINE-NEXT: Stmt_then
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; NO-NONEAFFINE-NEXT: Domain :=
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; NO-NONEAFFINE-NEXT: [p_0, p] -> { Stmt_then[] : p >= 2 + p_0 or p <= p_0 };
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; NO-NONEAFFINE-NEXT: Schedule :=
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; NO-NONEAFFINE-NEXT: [p_0, p] -> { Stmt_then[] -> [] };
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; NO-NONEAFFINE-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 0]
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; NO-NONEAFFINE-NEXT: [p_0, p] -> { Stmt_then[] -> MemRef_A[0] };
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; NO-NONEAFFINE-NEXT: }
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; NO-NONEAFFINE: Statements {
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; NO-NONEAFFINE-NEXT: Stmt_loop
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; NO-NONEAFFINE-NEXT: Domain :=
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; NO-NONEAFFINE-NEXT: [p] -> { Stmt_loop[0] : p = 100 };
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; NO-NONEAFFINE-NEXT: Schedule :=
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; NO-NONEAFFINE-NEXT: [p] -> { Stmt_loop[i0] -> [0] };
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; NO-NONEAFFINE-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 0]
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; NO-NONEAFFINE-NEXT: [p] -> { Stmt_loop[i0] -> MemRef_A[0] };
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; NO-NONEAFFINE-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
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; NO-NONEAFFINE-NEXT: [p] -> { Stmt_loop[i0] -> MemRef_cmp[] };
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; NO-NONEAFFINE-NEXT: }
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; Verify that this test case does not crash -polly-scops. The problem in
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; this test case is that the branch instruction in %branch references
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; a scalar evolution expression for which no useful value can be computed at the
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; location %branch, as the loop %loop does not terminate. At some point, we
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; did not identify the branch condition as non-affine during scop detection.
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; This test verifies that we either model the branch condition as non-affine
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; region or only detect a smaller region if non-affine conditions are not
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; allowed.
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target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
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target triple = "aarch64--linux-android"
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define void @f(i16 %event, i8 %p, float* %A) {
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entry:
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br label %loop
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loop:
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%indvar = phi i8 [ 0, %entry ], [ %indvar.next, %loop ]
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%indvar.next = add i8 %indvar, 1
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store float 1.0, float* %A
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%cmp = icmp eq i8 %indvar.next, %p
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%possibly_infinite = icmp eq i8 100, %p
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br i1 %possibly_infinite, label %branch, label %loop
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branch:
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br i1 %cmp, label %end, label %then
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then:
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store float 1.0, float* %A
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br label %end
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end:
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unreachable
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}
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@ -0,0 +1,57 @@
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; RUN: opt %loadPolly -polly-scops -analyze < %s | \
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; RUN: FileCheck %s -check-prefix=NONAFFINE
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; RUN: opt %loadPolly -polly-scops -analyze \
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; RUN: -polly-allow-nonaffine-branches=false < %s | \
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; RUN: FileCheck %s -check-prefix=NO-NONEAFFINE
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; NONAFFINE: Printing analysis 'Polly - Create polyhedral description of Scops' for region: 'branch => end' in function 'f':
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; NONAFFINE-NEXT: Invalid Scop!
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; NONAFFINE-NEXT: Printing analysis 'Polly - Create polyhedral description of Scops' for region: 'loop => branch' in function 'f':
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; NONAFFINE-NEXT: Invalid Scop!
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; NONAFFINE-NEXT: Printing analysis 'Polly - Create polyhedral description of Scops' for region: 'loop => end' in function 'f':
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; NONAFFINE-NEXT: Invalid Scop!
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; NONAFFINE-NEXT: Printing analysis 'Polly - Create polyhedral description of Scops' for region: 'entry => <Function Return>' in function 'f':
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; NONAFFINE-NEXT: Invalid Scop!
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; NO-NONEAFFINE: Statements {
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; NO-NONEAFFINE-NEXT: Stmt_then
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; NO-NONEAFFINE-NEXT: Domain :=
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; NO-NONEAFFINE-NEXT: [p_0] -> { Stmt_then[] : p_0 <= -2 or p_0 >= 0 };
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; NO-NONEAFFINE-NEXT: Schedule :=
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; NO-NONEAFFINE-NEXT: [p_0] -> { Stmt_then[] -> [] };
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; NO-NONEAFFINE-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 0]
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; NO-NONEAFFINE-NEXT: [p_0] -> { Stmt_then[] -> MemRef_A[0] };
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; NO-NONEAFFINE-NEXT: }
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; Verify that this test case does not crash -polly-scops. The problem in
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; this test case is that the branch instruction in %branch references
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; a scalar evolution expression for which no useful value can be computed at the
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; location %branch, as the loop %loop does not terminate. At some point, we
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; did not identify the branch condition as non-affine during scop detection.
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; This test verifies that we either model the branch condition as non-affine
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; region (and return an empty scop) or only detect a smaller region if
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; non-affine conditions are not allowed.
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target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
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target triple = "aarch64--linux-android"
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define void @f(i16 %event, float* %A) {
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entry:
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br label %loop
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loop:
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%indvar = phi i8 [ 0, %entry ], [ %indvar.next, %loop ]
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%indvar.next = add i8 %indvar, 1
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%cmp = icmp eq i8 %indvar.next, 0
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br i1 false, label %branch, label %loop
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branch:
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br i1 %cmp, label %end, label %then
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then:
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store float 1.0, float* %A
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br label %end
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end:
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unreachable
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}
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