From c74808b9142aa7f62d387417aab266170950ffdd Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo@fhahn.com>
Date: Thu, 25 Jul 2019 20:48:13 +0000
Subject: [PredicateInfo] Replace pointer comparisons with deterministic
 compares.

Currently there are a few pointer comparisons in ValueDFS_Compare, which
can cause non-deterministic ordering when materializing values. There
are 2 cases this patch fixes:

1. Order defs before uses used to compare pointers, which guarantees
   defs before uses, but causes non-deterministic ordering between 2
   uses or 2 defs, depending on the allocation order. By converting the
   pointers to booleans, we can circumvent that problem.

2. comparePHIRelated was comparing the basic block pointers of edges,
   which also results in a non-deterministic order and is also not
   really meaningful for ordering. By ordering by their destination DFS
   numbers we guarantee a deterministic order.

For the example below, we can end up with 2 different uselist orderings,
when running `opt -mem2reg -ipsccp` hundreds of times. Because the
non-determinism is caused by allocation ordering, we cannot reproduce it
with ipsccp alone.

    declare i32 @hoge() local_unnamed_addr #0

    define dso_local i32 @ham(i8* %arg, i8* %arg1) #0 {
    bb:
      %tmp = alloca i32
      %tmp2 = alloca i32, align 4
      br label %bb19

    bb4:                                              ; preds = %bb20
      br label %bb6

    bb6:                                              ; preds = %bb4
      %tmp7 = call i32 @hoge()
      store i32 %tmp7, i32* %tmp
      %tmp8 = load i32, i32* %tmp
      %tmp9 = icmp eq i32 %tmp8, 912730082
      %tmp10 = load i32, i32* %tmp
      br i1 %tmp9, label %bb11, label %bb16

    bb11:                                             ; preds = %bb6
      unreachable

    bb13:                                             ; preds = %bb20
      br label %bb14

    bb14:                                             ; preds = %bb13
      %tmp15 = load i32, i32* %tmp
      br label %bb16

    bb16:                                             ; preds = %bb14, %bb6
      %tmp17 = phi i32 [ %tmp10, %bb6 ], [ 0, %bb14 ]
      br label %bb19

    bb18:                                             ; preds = %bb20
      unreachable

    bb19:                                             ; preds = %bb16, %bb
      br label %bb20

    bb20:                                             ; preds = %bb19
      indirectbr i8* null, [label %bb4, label %bb13, label %bb18]
    }

Reviewers: davide, efriedma

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D64866

llvm-svn: 367049
---
 llvm/test/Transforms/SCCP/ipsccp-predinfo-order.ll | 76 ++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 llvm/test/Transforms/SCCP/ipsccp-predinfo-order.ll

(limited to 'llvm/test')

diff --git a/llvm/test/Transforms/SCCP/ipsccp-predinfo-order.ll b/llvm/test/Transforms/SCCP/ipsccp-predinfo-order.ll
new file mode 100644
index 00000000000..2474a19b097
--- /dev/null
+++ b/llvm/test/Transforms/SCCP/ipsccp-predinfo-order.ll
@@ -0,0 +1,76 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -ipsccp -S %s | FileCheck %s
+
+declare i32 @hoge()
+
+define dso_local i32 @ham(i8* %arg, i8* %arg1) {
+; CHECK-LABEL: @ham(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[TMP:%.*]] = alloca i32
+; CHECK-NEXT:    [[TMP2:%.*]] = alloca i32, align 4
+; CHECK-NEXT:    br label [[BB19:%.*]]
+; CHECK:       bb4:
+; CHECK-NEXT:    br label [[BB6:%.*]]
+; CHECK:       bb6:
+; CHECK-NEXT:    [[TMP7:%.*]] = call i32 @hoge()
+; CHECK-NEXT:    store i32 [[TMP7]], i32* [[TMP]]
+; CHECK-NEXT:    [[TMP8:%.*]] = load i32, i32* [[TMP]]
+; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i32 [[TMP8]], 912730082
+; CHECK-NEXT:    [[TMP10:%.*]] = load i32, i32* [[TMP]]
+; CHECK-NEXT:    br i1 [[TMP9]], label [[BB11:%.*]], label [[BB16:%.*]]
+; CHECK:       bb11:
+; CHECK-NEXT:    unreachable
+; CHECK:       bb13:
+; CHECK-NEXT:    br label [[BB14:%.*]]
+; CHECK:       bb14:
+; CHECK-NEXT:    [[TMP15:%.*]] = load i32, i32* [[TMP]]
+; CHECK-NEXT:    br label [[BB16]]
+; CHECK:       bb16:
+; CHECK-NEXT:    [[TMP17:%.*]] = phi i32 [ [[TMP10]], [[BB6]] ], [ 0, [[BB14]] ]
+; CHECK-NEXT:    br label [[BB19]]
+; CHECK:       bb18:
+; CHECK-NEXT:    unreachable
+; CHECK:       bb19:
+; CHECK-NEXT:    br label [[BB20:%.*]]
+; CHECK:       bb20:
+; CHECK-NEXT:    indirectbr i8* null, [label [[BB4:%.*]], label [[BB13:%.*]], label %bb18]
+;
+bb:
+  %tmp = alloca i32
+  %tmp2 = alloca i32, align 4
+  br label %bb19
+
+bb4:                                              ; preds = %bb20
+  br label %bb6
+
+bb6:                                              ; preds = %bb4
+  %tmp7 = call i32 @hoge()
+  store i32 %tmp7, i32* %tmp
+  %tmp8 = load i32, i32* %tmp
+  %tmp9 = icmp eq i32 %tmp8, 912730082
+  %tmp10 = load i32, i32* %tmp
+  br i1 %tmp9, label %bb11, label %bb16
+
+bb11:                                             ; preds = %bb6
+  unreachable
+
+bb13:                                             ; preds = %bb20
+  br label %bb14
+
+bb14:                                             ; preds = %bb13
+  %tmp15 = load i32, i32* %tmp
+  br label %bb16
+
+bb16:                                             ; preds = %bb14, %bb6
+  %tmp17 = phi i32 [ %tmp10, %bb6 ], [ 0, %bb14 ]
+  br label %bb19
+
+bb18:                                             ; preds = %bb20
+  unreachable
+
+bb19:                                             ; preds = %bb16, %bb
+  br label %bb20
+
+bb20:                                             ; preds = %bb19
+  indirectbr i8* null, [label %bb4, label %bb13, label %bb18]
+}
-- 
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