df8e140349
This patch removes the heuristic in
- Polly :: lib/Support/ScopHelper.cpp
The heuristic forces blocks that directly follow a loop header to not to be considered error blocks.
It was introduced in r249611 with the following commit message:
> This replaces the support for user defined error functions by a
> heuristic that tries to determine if a call to a non-pure function
> should be considered "an error". If so the block is assumed not to be
> executed at runtime. While treating all non-pure function calls as
> errors will allow a lot more regions to be analyzed, it will also
> cause us to dismiss a lot again due to an infeasible runtime context.
> This patch tries to limit that effect. A non-pure function call is
> considered an error if it is executed only in conditionally with
> regards to a cheap but simple heuristic.
In the code below `CCK_Abort2()` would be considered as an error block, but not `CCK_Abort1()` due to this heuristic.
```
for (int i = 0; i < n; i+=1) {
if (ErrorCondition1)
CCK_Abort1(); // No __attribute__((noreturn))
if (ErrorCondition2)
CCK_Abort2(); // No __attribute__((noreturn))
}
```
This does not seem useful. Checking error conditions in the beginning of some work is quite common. It causes a switch default-case to be not considered an error block in SPEC's cactuBSSN. The comment justifying the heuristic mentions a "load", which does not seem to be applicable here. It has been proposed to remove the heuristic.
In addition, the patch fixes the following test cases:
- Polly :: ScopDetect/mod_ref_read_pointer.ll
- Polly :: ScopInfo/max-loop-depth.ll
- Polly :: ScopInfo/mod_ref_access_pointee_arguments.ll
- Polly :: ScopInfo/mod_ref_read_pointee_arguments.ll
- Polly :: ScopInfo/mod_ref_read_pointer.ll
- Polly :: ScopInfo/mod_ref_read_pointers.ll
The test cases failed after removing the heuristic.
Differential Revision: https://reviews.llvm.org/D45274
Contributed-by: Lorenzo Chelini <l.chelini@icloud.com>
llvm-svn: 329548
43 lines
1.2 KiB
LLVM
43 lines
1.2 KiB
LLVM
; RUN: opt %loadPolly -basicaa -polly-detect -analyze \
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; RUN: -polly-allow-modref-calls < %s | FileCheck %s -check-prefix=MODREF
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; RUN: opt %loadPolly -basicaa -polly-detect -analyze \
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; RUN: < %s | FileCheck %s
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;
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; CHECK-NOT: Valid Region for Scop: for.body => for.end
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; MODREF: Valid Region for Scop: for.body => for.end
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;
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; #pragma readonly
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; int func(int *A);
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;
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; void jd(int *A) {
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; for (int i = 0; i < 1024; i++)
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; A[i + 2] = func(A);
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; }
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;
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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declare i32 @func(i32* %A) #1
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define void @jd(i32* %A) {
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.inc
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%i = phi i64 [ 0, %entry ], [ %i.next, %for.inc ]
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%call = call i32 @func(i32* %A)
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%tmp = add nsw i64 %i, 2
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%arrayidx = getelementptr inbounds i32, i32* %A, i64 %tmp
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store i32 %call, i32* %arrayidx, align 4
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br label %for.inc
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for.inc: ; preds = %for.body
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%i.next = add nuw nsw i64 %i, 1
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%exitcond = icmp ne i64 %i.next, 1024
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br i1 %exitcond, label %for.body, label %for.end
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for.end: ; preds = %for.inc
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ret void
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}
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attributes #1 = { nounwind readonly }
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