[CodeGen] avoid broken successor probability in MBB dump

[inouehrs]

Summary

When printing successor probabilities for a MBB, a human readble value is somethimes shown as 200%.
The human readble 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.

Example of broken probability

bb.1.if.then:
; predecessors: %bb.0
  successors: %bb.3(0x80000000); %bb.3(200.00%)

[thegameg]

LGTM. It would be nice to have a test too.

llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp

for (auto I = succ_begin(), E = succ_end(); I != E; ++I) {
         OS << '('
            << format("0x%08" PRIx32, getSuccProbability(I).getNumerator())
            << ')';
     }
     if (!Probs.empty() && IsStandalone) {
       // 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) << '('
            << format("%.2f%%",
                      rint(((double)BP.getNumerator() / BP.getDenominator()) *
                           100.0 * 100.0) /
                          100.0)
            << ')';

llvm/trunk/test/Other/X86/mbb-dump.ll

+; 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
+}