llvm-project/polly/test/DependenceInfo/reduction_simple_iv_debug_w...

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; RUN: opt %loadPolly -polly-dependences -analyze -debug-only=polly-dependence 2>&1 < %s | FileCheck %s
;
; REQUIRES: asserts
;
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; CHECK: Read: { [Stmt_for_cond[i0] -> MemRef_sum[0{{\]\]}} -> MemRef_sum[0] : 0 <= i0 <= 100 }
; CHECK-NEXT: Write: { [Stmt_for_cond[i0] -> MemRef_sum[0{{\]\]}} -> MemRef_sum[0] : 0 <= i0 <= 100 }
; CHECK-NEXT: MayWrite: { }
;
; CHECK: Wrapped Dependences:
; CHECK-NEXT: RAW dependences:
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; CHECK-NEXT: { [Stmt_for_cond[i0] -> MemRef_sum[0{{\]\]}} -> [Stmt_for_cond[1 + i0] -> MemRef_sum[0{{\]\]}} : 0 <= i0 <= 99 }
; CHECK-NEXT: WAR dependences:
[Polly] [DependenceInfo] change WAR, WAW generation to correct semantics = Change of WAR, WAW generation: = - `buildFlow(Sink, MustSource, MaySource, Sink)` treates any flow of the form `sink <- may source <- must source` as a *may* dependence. - we used to call: ```lang=cpp, name=old-flow-call.cpp Flow = buildFlow(MustWrite, MustWrite, Read, Schedule); WAW = isl_union_flow_get_must_dependence(Flow); WAR = isl_union_flow_get_may_dependence(Flow); ``` - This caused some WAW dependences to be treated as WAR dependences. - Incorrect semantics. - Now, we call WAR and WAW correctly. == Correct WAW: == ```lang=cpp, name=new-waw-call.cpp Flow = buildFlow(Write, MustWrite, MayWrite, Schedule); WAW = isl_union_flow_get_may_dependence(Flow); isl_union_flow_free(Flow); ``` == Correct WAR: == ```lang=cpp, name=new-war-call.cpp Flow = buildFlow(Write, Read, MustaWrite, Schedule); WAR = isl_union_flow_get_must_dependence(Flow); isl_union_flow_free(Flow); ``` - We want the "shortest" WAR possible (exact dependences). - We mark all the *must-writes* as may-source, reads as must-souce. - Then, we ask for *must* dependence. - This removes all the reads that flow through a *must-write* before reaching a sink. - Note that we only block ealier writes with *must-writes*. This is intuitively correct, as we do not want may-writes to block must-writes. - Leaves us with direct (R -> W). - This affects reduction generation since RED is built using WAW and WAR. = New StrictWAW for Reductions: = - We used to call: ```lang=cpp,name=old-waw-war-call.cpp Flow = buildFlow(MustWrite, MustWrite, Read, Schedule); WAW = isl_union_flow_get_must_dependence(Flow); WAR = isl_union_flow_get_may_dependence(Flow); ``` - This *is* the right model of WAW we need for reductions, just not in general. - Reductions need to track only *strict* WAW, without any interfering reductions. = Explanation: Why the new WAR dependences in tests are correct: = - We no longer set WAR = WAR - WAW - Hence, we will have WAR dependences that were originally removed. - These may look incorrect, but in fact make sense. == Code: == ```lang=llvm, name=new-war-dependence.ll ; void manyreductions(long *A) { ; for (long i = 0; i < 1024; i++) ; for (long j = 0; j < 1024; j++) ; S0: *A += 42; ; ; for (long i = 0; i < 1024; i++) ; for (long j = 0; j < 1024; j++) ; S1: *A += 42; ; ``` === WAR dependence: === { S0[1023, 1023] -> S1[0, 0] } - Between `S0[1023, 1023]` and `S1[0, 0]`, we will have the dependences: ```lang=cpp, name=dependence-incorrect, counterexample S0[1023, 1023]: *-- tmp = *A (load0)--* WAR 2 add = tmp + 42 | *-> *A = add (store0) | WAR 1 S1[0, 0]: | tmp = *A (load1) | add = tmp + 42 | A = add (store1)<-* ``` - One may assume that WAR2 *hides* WAR1 (since store0 happens before store1). However, within a statement, Polly has no idea about the ordering of loads and stores. - Hence, according to Polly, the code may have looked like this: ```lang=cpp, name=dependence-correct S0[1023, 1023]: A = add (store0) tmp = A (load0) ---* add = A + 42 | WAR 1 S1[0, 0]: | tmp = A (load1) | add = A + 42 | A = add (store1) <-* ``` - So, Polly generates (correct) WAR dependences. It does not make sense to remove these dependences, since they are correct with respect to Polly's model. Reviewers: grosser, Meinersbur tags: #polly Differential revision: https://reviews.llvm.org/D31386 llvm-svn: 299429
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; CHECK-NEXT: { [Stmt_for_cond[i0] -> MemRef_sum[0{{\]\]}} -> [Stmt_for_cond[1 + i0] -> MemRef_sum[0{{\]\]}} : 0 <= i0 <= 99 }
; CHECK-NEXT: WAW dependences:
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; CHECK-NEXT: { [Stmt_for_cond[i0] -> MemRef_sum[0{{\]\]}} -> [Stmt_for_cond[1 + i0] -> MemRef_sum[0{{\]\]}} : 0 <= i0 <= 99 }
; CHECK-NEXT: Reduction dependences:
; CHECK-NEXT: n/a
;
; CHECK: Final Wrapped Dependences:
; CHECK-NEXT: RAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAR dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: Reduction dependences:
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; CHECK-NEXT: { [Stmt_for_cond[i0] -> MemRef_sum[0{{\]\]}} -> [Stmt_for_cond[1 + i0] -> MemRef_sum[0{{\]\]}} : 0 <= i0 <= 99 }
;
; CHECK: Zipped Dependences:
; CHECK-NEXT: RAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAR dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: Reduction dependences:
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; CHECK-NEXT: { [Stmt_for_cond[i0] -> Stmt_for_cond[1 + i0{{\]\]}} -> [MemRef_sum[0] -> MemRef_sum[0{{\]\]}} : 0 <= i0 <= 99 }
;
; CHECK: Unwrapped Dependences:
; CHECK-NEXT: RAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAR dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: Reduction dependences:
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; CHECK-NEXT: { Stmt_for_cond[i0] -> Stmt_for_cond[1 + i0] : 0 <= i0 <= 99 }
;
; CHECK: RAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAR dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: Reduction dependences:
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; CHECK-NEXT: { Stmt_for_cond[i0] -> Stmt_for_cond[1 + i0] : 0 <= i0 <= 99 }
;
; CHECK: RAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAR dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: WAW dependences:
; CHECK-NEXT: { }
; CHECK-NEXT: Reduction dependences:
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; CHECK-NEXT: { Stmt_for_cond[i0] -> Stmt_for_cond[1 + i0] : 0 <= i0 <= 99 }
;
; void f(int* sum) {
; for (int i = 0; i <= 100; i++)
; sum += i * 3;
; }
target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-n32-S64"
define void @f(i32* %sum) {
entry:
br label %entry.split1
entry.split1: ; preds = %entry
br label %entry.split
entry.split: ; preds = %entry.split1
br label %for.cond
for.cond: ; preds = %for.cond, %entry.split
%i1.0 = phi i32 [ 0, %entry.split ], [ %inc, %for.cond ]
%sum.reload = load i32, i32* %sum
%mul = mul nsw i32 %i1.0, 3
%add = add nsw i32 %sum.reload, %mul
%inc = add nsw i32 %i1.0, 1
store i32 %add, i32* %sum
%cmp = icmp slt i32 %i1.0, 100
br i1 %cmp, label %for.cond, label %for.end
for.end: ; preds = %for.cond
ret void
}