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llvm-project/llvm/test/Transforms/CanonicalizeFreezeInLoops/phis.ll

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Add CanonicalizeFreezeInLoops pass Summary: If an induction variable is frozen and used, SCEV yields imprecise result because it doesn't say anything about frozen variables. Due to this reason, performance degradation happened after https://reviews.llvm.org/D76483 is merged, causing SCEV yield imprecise result and preventing LSR to optimize a loop. The suggested solution here is to add a pass which canonicalizes frozen variables inside a loop. To be specific, it pushes freezes out of the loop by freezing the initial value and step values instead & dropping nsw/nuw flags from instructions used by freeze. This solution was also mentioned at https://reviews.llvm.org/D70623 . Reviewers: spatel, efriedma, lebedev.ri, fhahn, jdoerfert Reviewed By: fhahn Subscribers: nikic, mgorny, hiraditya, javed.absar, llvm-commits, sanwou01, nlopes Tags: #llvm Differential Revision: https://reviews.llvm.org/D77523
2020-05-08 04:28:42 +08:00
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -canon-freeze -S | FileCheck %s
; A set of tests that have several phi nodes
declare void @call(i32)
declare i32 @call2()
define void @onephi_used(i32 %n, i32 %i.init, i32 %j.init) {
; CHECK-LABEL: @onephi_used(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[I_INIT_FROZEN:%.*]] = freeze i32 [[I_INIT:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ [[I_INIT_FROZEN]], [[ENTRY:%.*]] ], [ [[I_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[J:%.*]] = phi i32 [ [[J_INIT:%.*]], [[ENTRY]] ], [ [[J_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[I_NEXT]] = add i32 [[I]], 1
; CHECK-NEXT: [[J_NEXT]] = add nuw nsw i32 [[J]], -2
; CHECK-NEXT: call void @call(i32 [[I]])
; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[I_NEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[COND]], label [[LOOP]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop
loop:
%i = phi i32 [ %i.init, %entry ], [ %i.next, %loop ]
%j = phi i32 [ %j.init, %entry ], [ %j.next, %loop ]
%i.next = add nuw nsw i32 %i, 1
%j.next = add nuw nsw i32 %j, -2
%i.fr = freeze i32 %i
call void @call(i32 %i.fr)
%cond = icmp eq i32 %i.next, %n
br i1 %cond, label %loop, label %exit
exit:
ret void
}
; Negative test
define void @twophis_used(i32 %n, i32 %i.init, i32 %j.init) {
; CHECK-LABEL: @twophis_used(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ [[I_INIT:%.*]], [[ENTRY:%.*]] ], [ [[I_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[J:%.*]] = phi i32 [ [[J_INIT:%.*]], [[ENTRY]] ], [ [[J_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[I_NEXT]] = add nuw nsw i32 [[I]], 1
; CHECK-NEXT: [[J_NEXT]] = add nuw nsw i32 [[J]], -2
; CHECK-NEXT: [[IJ:%.*]] = add i32 [[I]], [[J]]
; CHECK-NEXT: [[IJ_FR:%.*]] = freeze i32 [[IJ]]
; CHECK-NEXT: call void @call(i32 [[IJ_FR]])
; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[I_NEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[COND]], label [[LOOP]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop
loop:
%i = phi i32 [ %i.init, %entry ], [ %i.next, %loop ]
%j = phi i32 [ %j.init, %entry ], [ %j.next, %loop ]
%i.next = add nuw nsw i32 %i, 1
%j.next = add nuw nsw i32 %j, -2
%ij = add i32 %i, %j
%ij.fr = freeze i32 %ij
call void @call(i32 %ij.fr)
%cond = icmp eq i32 %i.next, %n
br i1 %cond, label %loop, label %exit
exit:
ret void
}
; Negative test
define void @nonindphi_used(i32 %n, i32 %i.init, i32 %j.init, i32 %k.init) {
; CHECK-LABEL: @nonindphi_used(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ [[I_INIT:%.*]], [[ENTRY:%.*]] ], [ [[I_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[J:%.*]] = phi i32 [ [[J_INIT:%.*]], [[ENTRY]] ], [ [[J_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[K:%.*]] = phi i32 [ [[K_INIT:%.*]], [[ENTRY]] ], [ [[ANY:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[I_NEXT]] = add nuw nsw i32 [[I]], 1
; CHECK-NEXT: [[J_NEXT]] = add nuw nsw i32 [[J]], -2
; CHECK-NEXT: [[IJ:%.*]] = add i32 [[I]], [[J]]
; CHECK-NEXT: [[IJK:%.*]] = add i32 [[IJ]], [[K]]
; CHECK-NEXT: [[IJK_FR:%.*]] = freeze i32 [[IJK]]
; CHECK-NEXT: call void @call(i32 [[IJK_FR]])
; CHECK-NEXT: [[ANY]] = call i32 @call2()
; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[I_NEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[COND]], label [[LOOP]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop
loop:
%i = phi i32 [ %i.init, %entry ], [ %i.next, %loop ]
%j = phi i32 [ %j.init, %entry ], [ %j.next, %loop ]
%k = phi i32 [ %k.init, %entry ], [ %any, %loop ]
%i.next = add nuw nsw i32 %i, 1
%j.next = add nuw nsw i32 %j, -2
%ij = add i32 %i, %j
%ijk = add i32 %ij, %k
%ijk.fr = freeze i32 %ijk
call void @call(i32 %ijk.fr)
%any = call i32 @call2()
%cond = icmp eq i32 %i.next, %n
br i1 %cond, label %loop, label %exit
exit:
ret void
}