[NFC][RemoveDIs] Prefer iterator-insertion over instructions

Continuing the patch series to get rid of debug intrinsics [0], instruction
insertion needs to be done with iterators rather than instruction pointers,
so that we can communicate information in the iterator class. This patch
adds an iterator-taking insertBefore method and converts various call sites
to take iterators. These are all sites where such debug-info needs to be
preserved so that a stage2 clang can be built identically; it's likely that
many more will need to be changed in the future.

At this stage, this is just changing the spelling of a few operations,
which will eventually become signifiant once the debug-info bearing
iterator is used.

[0] https://discourse.llvm.org/t/rfc-instruction-api-changes-needed-to-eliminate-debug-intrinsics-from-ir/68939

Differential Revision: https://reviews.llvm.org/D152537

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
index aee2243..d861216 100644
--- a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
@@ -1291,8 +1291,8 @@ Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) {
     // specified loop.
     BasicBlock *Header = L->getHeader();
     pred_iterator HPB = pred_begin(Header), HPE = pred_end(Header);
-    CanonicalIV = PHINode::Create(Ty, std::distance(HPB, HPE), "indvar",
-                                  &Header->front());
+    CanonicalIV = PHINode::Create(Ty, std::distance(HPB, HPE), "indvar");
+    CanonicalIV->insertBefore(Header->begin());
     rememberInstruction(CanonicalIV);
 
     SmallSet<BasicBlock *, 4> PredSeen;