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llvm-project/polly/test/Simplify/dead_access_phi.ll

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[ScopBuilder] Make -polly-stmt-granularity=scalar-indep the default. Splitting basic blocks into multiple statements if there are now additional scalar dependencies gives more freedom to the scheduler, but more statements also means higher compile-time complexity. Switch to finer statement granularity, the additional compile time should be limited by the number of operations quota. The regression tests are written for the -polly-stmt-granularity=bb setting, therefore we add that flag to those tests that break with the new default. Some of the tests only fail because the statements are named differently due to a basic block resulting in multiple statements, but which are removed during simplification of statements without side-effects. Previous commits tried to reduce this effect, but it is not completely avoidable. Differential Revision: https://reviews.llvm.org/D42151 llvm-svn: 324169
2018-02-03 14:59:47 +08:00
; RUN: opt %loadPolly -polly-stmt-granularity=bb -polly-simplify -analyze < %s | FileCheck %s -match-full-lines
[Simplify] Remove unused instructions and accesses. Use a mark-and-sweep algorithm to find and remove unused instructions and MemoryAccesses. This is useful in particular to remove scalar writes that are never used anywhere. A scalar write in a loop induces a write-after-write dependency that stops the loop iterations to be rescheduled. Such writes can be a result of previous transformations such as DeLICM and operand tree forwarding. It adds a new class VirtualInstruction that represents an instruction in a particular statement. At the moment an instruction can only belong to the statement that represents a BasicBlock. In the future, instructions can be in one of multiple statements representing a BasicBlock (Nandini's work), in different statements than its BasicBlock would indicate, and even multiple statements at once (by forwarding operand trees). It also integrates nicely with the VirtualUse class. ScopStmt::contains(Instruction*) currently uses the instruction's parent BasicBlock to check whether it contains the instruction. It will need to check the actual statement list when one of the aforementioned features become possible. Differential Revision: https://reviews.llvm.org/D35656 llvm-svn: 308626
2017-07-21 00:21:55 +08:00
;
; Remove a dead PHI write/read pair
; (accesses that are effectively not used)
;
; for (int j = 0; j < n; j += 1) {
; body:
; double phi = 42;
;
; body_succ:
; A[0] = 42.0;
; }
;
define void @func(i32 %n, double* noalias nonnull %A) {
entry:
br label %for
for:
%j = phi i32 [0, %entry], [%j.inc, %inc]
%j.cmp = icmp slt i32 %j, %n
br i1 %j.cmp, label %body, label %exit
body:
br label %body_succ
body_succ:
%phi = phi double [42.0, %body]
store double 42.0, double* %A
br label %inc
inc:
%j.inc = add nuw nsw i32 %j, 1
br label %for
exit:
br label %return
return:
ret void
}
; CHECK: Statistics {
; CHECK: Dead accesses removed: 2
; CHECK: Dead instructions removed: 1
; CHECK: Stmts removed: 1
; CHECK: }
; CHECK: After accesses {
; CHECK-NEXT: Stmt_body_succ
; CHECK-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 0]
; CHECK-NEXT: [n] -> { Stmt_body_succ[i0] -> MemRef_A[0] };
; CHECK-NEXT: }