PGO branch weight: update edge weights in IfConverter.

This commit only handles IfConvertTriangle. To update edge weights
of a successor, one interface is added to MachineBasicBlock:
/// Set successor weight of a given iterator.
setSuccWeight(succ_iterator I, uint32_t weight)

An existing testing case test/CodeGen/Thumb2/v8_IT_5.ll is updated,
since we now correctly update the edge weights, the cold block
is placed at the end of the function and we jump to the cold block.

llvm-svn: 200428

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 5bd47c2f1d2..d2df4e5cb8b 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -1123,6 +1123,13 @@ uint32_t MachineBasicBlock::getSuccWeight(const_succ_iterator Succ) const {
   return *getWeightIterator(Succ);
 }
 
+/// Set successor weight of a given iterator.
+void MachineBasicBlock::setSuccWeight(succ_iterator I, uint32_t weight) {
+  if (Weights.empty())
+    return;
+  *getWeightIterator(I) = weight;
+}
+
 /// getWeightIterator - Return wight iterator corresonding to the I successor
 /// iterator
 MachineBasicBlock::weight_iterator MachineBasicBlock::