[CodeGen] fix broken successor probability in MBB dump

When printing successor probabilities for a MBB, a human readable value is sometimes shown as 200.0%.
The human readable output is based on getProbabilityIterator, which returns 0xFFFFFFFF for getNumerator() and 0x80000000 for getDenominator() for unknown BranchProbability.
By using getSuccProbability as we do for the non-human readable part, we can avoid this problem.

Differential Revision: https://reviews.llvm.org/D52605



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@343297 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachineBasicBlock.cpp

@@ -362,7 +362,7 @@ void MachineBasicBlock::print(raw_ostream &OS, ModuleSlotTracker &MST,
       // Print human readable probabilities as comments.
       OS << "; ";
       for (auto I = succ_begin(), E = succ_end(); I != E; ++I) {
-        const BranchProbability &BP = *getProbabilityIterator(I);
+        const BranchProbability &BP = getSuccProbability(I);
         if (I != succ_begin())
           OS << ", ";
         OS << printMBBReference(**I) << '('

test/Other/X86/mbb-dump.ll

@@ -0,0 +1,25 @@
+; RUN: llc < %s 2>&1 -print-after=machine-scheduler -mtriple=x86_64-unknown-unknown | FileCheck %s
+
+; expected MBB dump output
+; # *** IR Dump After Machine Instruction Scheduler ***:
+; # Machine code for function foo: NoPHIs, TracksLiveness
+; 
+; 0B	bb.0 (%ir-block.0):
+; 	  successors: %bb.1(0x80000000); %bb.1(100.00%)
+; 
+; 16B	bb.1.next:
+; 	; predecessors: %bb.0
+
+; previously, it was broken as
+; 	  successors: %bb.1(0x80000000); %bb.1(200.00%)
+
+define void @foo(){
+; CHECK: IR Dump After Machine Instruction Scheduler
+; CHECK: bb.0
+; CHECK: 100.0
+; CHECK: bb.1
+  br label %next
+
+next:
+  ret void
+}