From 93702a3b0754052d926c75082abf7ca156b80c45 Mon Sep 17 00:00:00 2001
From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Fri, 21 Jun 2013 19:30:05 +0000
Subject: BlockFrequency: Saturate at 1 instead of 0 when multiplying a
 frequency with a branch probability.

Zero is used by BlockFrequencyInfo as a special "don't know" value. It also
causes a sink for frequencies as you can't ever get off a zero frequency with
more multiplies.

This recovers a 10% regression on MultiSource/Benchmarks/7zip. A zero frequency
was propagated into an inner loop causing excessive spilling.

PR16402.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184584 91177308-0d34-0410-b5e6-96231b3b80d8
---
 test/Analysis/BlockFrequencyInfo/singularity.ll | 65 +++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 test/Analysis/BlockFrequencyInfo/singularity.ll

(limited to 'test/Analysis')

diff --git a/test/Analysis/BlockFrequencyInfo/singularity.ll b/test/Analysis/BlockFrequencyInfo/singularity.ll
new file mode 100644
index 0000000000..9077cc0656
--- /dev/null
+++ b/test/Analysis/BlockFrequencyInfo/singularity.ll
@@ -0,0 +1,65 @@
+; RUN: opt < %s -analyze -block-freq | FileCheck %s
+; PR16402
+
+define void @test1(i32 %n) nounwind {
+entry:
+  %call = tail call i32* @cond() nounwind
+  %tobool = icmp eq i32* %call, null
+  br i1 %tobool, label %land.lhs.true, label %if.end
+
+land.lhs.true:                                    ; preds = %entry
+  %call1 = tail call i32* @cond() nounwind
+  %tobool2 = icmp eq i32* %call1, null
+  br i1 %tobool2, label %land.lhs.true3, label %if.end
+
+land.lhs.true3:                                   ; preds = %land.lhs.true
+  %call4 = tail call i32* @cond() nounwind
+  %tobool5 = icmp eq i32* %call4, null
+  br i1 %tobool5, label %land.lhs.true6, label %if.end
+
+land.lhs.true6:                                   ; preds = %land.lhs.true3
+  %call7 = tail call i32* @cond() nounwind
+  %tobool8 = icmp eq i32* %call7, null
+  br i1 %tobool8, label %land.lhs.true9, label %if.end
+
+land.lhs.true9:                                   ; preds = %land.lhs.true6
+  %call10 = tail call i32* @cond() nounwind
+  %tobool11 = icmp eq i32* %call10, null
+  br i1 %tobool11, label %land.lhs.true12, label %if.end
+
+land.lhs.true12:                                  ; preds = %land.lhs.true9
+  %call13 = tail call i32* @cond() nounwind
+  %tobool14 = icmp eq i32* %call13, null
+  br i1 %tobool14, label %land.lhs.true15, label %if.end
+
+land.lhs.true15:                                  ; preds = %land.lhs.true12
+  %call16 = tail call i32* @cond() nounwind
+  %tobool17 = icmp eq i32* %call16, null
+  br i1 %tobool17, label %for.cond.preheader, label %if.end
+
+for.cond.preheader:                               ; preds = %land.lhs.true15
+  %cmp21 = icmp eq i32 %n, 0
+  br i1 %cmp21, label %for.end, label %for.body
+
+for.body:                                         ; preds = %for.cond.preheader, %for.body
+  %i.022 = phi i32 [ %inc, %for.body ], [ 0, %for.cond.preheader ]
+  %call18 = tail call i32 @call() nounwind
+  %inc = add nsw i32 %i.022, 1
+  %cmp = icmp eq i32 %inc, %n
+  br i1 %cmp, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body, %for.cond.preheader
+  %call19 = tail call i32* @cond() nounwind
+  br label %if.end
+
+if.end:                                           ; preds = %land.lhs.true15, %land.lhs.true12, %land.lhs.true9, %land.lhs.true6, %land.lhs.true3, %land.lhs.true, %entry, %for.end
+  ret void
+
+; CHECK: entry = 1024
+; CHECK-NOT: for.body = 0
+; CHECK-NOT: for.end = 0
+}
+
+declare i32* @cond() nounwind
+
+declare i32 @call() nounwind
-- 
cgit v1.2.3