BFI: Saturate when combining edges to a successor

When a loop gets bundled up, its outgoing edges are quite large, and can
just barely overflow 64-bits.  If one successor has multiple incoming
edges -- and that successor is getting all the incoming mass --
combining just its edges can overflow.  Handle that by saturating rather
than asserting.

This fixes PR21622.

llvm-svn: 223500

1 files changed, 40 insertions, 0 deletions

diff --git a/llvm/test/Analysis/BlockFrequencyInfo/extremely-likely-loop-successor.ll b/llvm/test/Analysis/BlockFrequencyInfo/extremely-likely-loop-successor.ll
new file mode 100644
index 00000000000..f1ddd13ef0d
--- /dev/null
+++ b/llvm/test/Analysis/BlockFrequencyInfo/extremely-likely-loop-successor.ll
@@ -0,0 +1,40 @@
+; RUN: opt < %s -analyze -block-freq | FileCheck %s
+
+; PR21622: Check for a crasher when the sum of exits to the same successor of a
+; loop overflows.
+
+; CHECK-LABEL: Printing analysis {{.*}} for function 'extremely_likely_loop_successor':
+; CHECK-NEXT: block-frequency-info: extremely_likely_loop_successor
+define void @extremely_likely_loop_successor() {
+; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
+entry:
+  br label %loop
+
+; CHECK-NEXT: loop: float = 1.0,
+loop:
+  %exit.1.cond = call i1 @foo()
+  br i1 %exit.1.cond, label %exit, label %loop.2, !prof !0
+
+; CHECK-NEXT: loop.2: float = 0.0000000
+loop.2:
+  %exit.2.cond = call i1 @foo()
+  br i1 %exit.2.cond, label %exit, label %loop.3, !prof !0
+
+; CHECK-NEXT: loop.3: float = 0.0000000
+loop.3:
+  %exit.3.cond = call i1 @foo()
+  br i1 %exit.3.cond, label %exit, label %loop.4, !prof !0
+
+; CHECK-NEXT: loop.4: float = 0.0,
+loop.4:
+  %exit.4.cond = call i1 @foo()
+  br i1 %exit.4.cond, label %exit, label %loop, !prof !0
+
+; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
+exit:
+  ret void
+}
+
+declare i1 @foo()
+
+!0 = metadata !{metadata !"branch_weights", i32 4294967295, i32 1}