[SCEV] Update interface to handle SCEVExpander insert point motion.

Summary:
This is an extension of the fix in r271424.  That fix dealt with builder
insert points being moved by SCEV expansion, but only for the lifetime
of the expand call.  This change modifies the interface so that LSR can
safely call expand multiple times at the same insert point and do the
right thing if one of the expansions decides to move the original insert
point.

This is a fix for PR28719.

Reviewers: sanjoy

Subscribers: llvm-commits, mcrosier, mzolotukhin

Differential Revision: https://reviews.llvm.org/D23342

llvm-svn: 278413

1 files changed, 9 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index c2a8f15..2542193 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -4444,6 +4444,7 @@ Value *LSRInstance::Expand(const LSRFixup &LF,
   // Determine an input position which will be dominated by the operands and
   // which will dominate the result.
   IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
+  Rewriter.setInsertPoint(&*IP);
 
   // Inform the Rewriter if we have a post-increment use, so that it can
   // perform an advantageous expansion.
@@ -4475,7 +4476,7 @@ Value *LSRInstance::Expand(const LSRFixup &LF,
                                  LF.UserInst, LF.OperandValToReplace,
                                  Loops, SE, DT);
 
-    Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr, &*IP)));
+    Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
   }
 
   // Expand the ScaledReg portion.
@@ -4493,14 +4494,14 @@ Value *LSRInstance::Expand(const LSRFixup &LF,
       // Expand ScaleReg as if it was part of the base regs.
       if (F.Scale == 1)
         Ops.push_back(
-            SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr, &*IP)));
+            SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
       else {
         // An interesting way of "folding" with an icmp is to use a negated
         // scale, which we'll implement by inserting it into the other operand
         // of the icmp.
         assert(F.Scale == -1 &&
                "The only scale supported by ICmpZero uses is -1!");
-        ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr, &*IP);
+        ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
       }
     } else {
       // Otherwise just expand the scaled register and an explicit scale,
@@ -4510,11 +4511,11 @@ Value *LSRInstance::Expand(const LSRFixup &LF,
       // Unless the addressing mode will not be folded.
       if (!Ops.empty() && LU.Kind == LSRUse::Address &&
           isAMCompletelyFolded(TTI, LU, F)) {
-        Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, &*IP);
+        Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
         Ops.clear();
         Ops.push_back(SE.getUnknown(FullV));
       }
-      ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr, &*IP));
+      ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
       if (F.Scale != 1)
         ScaledS =
             SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
@@ -4526,7 +4527,7 @@ Value *LSRInstance::Expand(const LSRFixup &LF,
   if (F.BaseGV) {
     // Flush the operand list to suppress SCEVExpander hoisting.
     if (!Ops.empty()) {
-      Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, &*IP);
+      Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
       Ops.clear();
       Ops.push_back(SE.getUnknown(FullV));
     }
@@ -4536,7 +4537,7 @@ Value *LSRInstance::Expand(const LSRFixup &LF,
   // Flush the operand list to suppress SCEVExpander hoisting of both folded and
   // unfolded offsets. LSR assumes they both live next to their uses.
   if (!Ops.empty()) {
-    Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, &*IP);
+    Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
     Ops.clear();
     Ops.push_back(SE.getUnknown(FullV));
   }
@@ -4572,7 +4573,7 @@ Value *LSRInstance::Expand(const LSRFixup &LF,
   const SCEV *FullS = Ops.empty() ?
                       SE.getConstant(IntTy, 0) :
                       SE.getAddExpr(Ops);
-  Value *FullV = Rewriter.expandCodeFor(FullS, Ty, &*IP);
+  Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
 
   // We're done expanding now, so reset the rewriter.
   Rewriter.clearPostInc();