From 7bd839f42ba5100cd48dead581fdcad9523d0dee Mon Sep 17 00:00:00 2001
From: Evgeny Astigeevich <evgeny.astigeevich@arm.com>
Date: Tue, 3 Oct 2017 12:00:40 +0000
Subject: [PATCH] [InlineCost, NFC] Extract code dealing with inbounds GEPs
 from visitGetElementPtr into a function

The code responsible for analysis of inbounds GEPs is extracted into a separate
function: CallAnalyzer::canFoldInboundsGEP. With the patch SROA
enabling/disabling code is localized at one place instead of spreading across
the code of CallAnalyzer::visitGetElementPtr.

Differential Revision: https://reviews.llvm.org/D38233


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@314787 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/InlineCost.cpp | 53 ++++++++++++++++++++-------------------------
 1 file changed, 24 insertions(+), 29 deletions(-)

diff --git a/lib/Analysis/InlineCost.cpp b/lib/Analysis/InlineCost.cpp
index 2ee75c83d70..db89fc2181a 100644
--- a/lib/Analysis/InlineCost.cpp
+++ b/lib/Analysis/InlineCost.cpp
@@ -172,6 +172,7 @@ class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
   void accumulateSROACost(DenseMap<Value *, int>::iterator CostIt,
                           int InstructionCost);
   bool isGEPFree(GetElementPtrInst &GEP);
+  bool canFoldInboundsGEP(GetElementPtrInst &I);
   bool accumulateGEPOffset(GEPOperator &GEP, APInt &Offset);
   bool simplifyCallSite(Function *F, CallSite CS);
   template <typename Callable>
@@ -431,40 +432,34 @@ bool CallAnalyzer::visitPHI(PHINode &I) {
   return true;
 }
 
+/// \brief Check we can fold GEPs of constant-offset call site argument pointers.
+/// This requires target data and inbounds GEPs.
+///
+/// \return true if the specified GEP can be folded.
+bool CallAnalyzer::canFoldInboundsGEP(GetElementPtrInst &I) {
+  // Check if we have a base + offset for the pointer.
+  std::pair<Value *, APInt> BaseAndOffset =
+      ConstantOffsetPtrs.lookup(I.getPointerOperand());
+  if (!BaseAndOffset.first)
+    return false;
+
+  // Check if the offset of this GEP is constant, and if so accumulate it
+  // into Offset.
+  if (!accumulateGEPOffset(cast<GEPOperator>(I), BaseAndOffset.second))
+    return false;
+
+  // Add the result as a new mapping to Base + Offset.
+  ConstantOffsetPtrs[&I] = BaseAndOffset;
+
+  return true;
+}
+
 bool CallAnalyzer::visitGetElementPtr(GetElementPtrInst &I) {
   Value *SROAArg;
   DenseMap<Value *, int>::iterator CostIt;
   bool SROACandidate =
       lookupSROAArgAndCost(I.getPointerOperand(), SROAArg, CostIt);
 
-  // Try to fold GEPs of constant-offset call site argument pointers. This
-  // requires target data and inbounds GEPs.
-  if (I.isInBounds()) {
-    // Check if we have a base + offset for the pointer.
-    Value *Ptr = I.getPointerOperand();
-    std::pair<Value *, APInt> BaseAndOffset = ConstantOffsetPtrs.lookup(Ptr);
-    if (BaseAndOffset.first) {
-      // Check if the offset of this GEP is constant, and if so accumulate it
-      // into Offset.
-      if (!accumulateGEPOffset(cast<GEPOperator>(I), BaseAndOffset.second)) {
-        // Non-constant GEPs aren't folded, and disable SROA.
-        if (SROACandidate)
-          disableSROA(CostIt);
-        return isGEPFree(I);
-      }
-
-      // Add the result as a new mapping to Base + Offset.
-      ConstantOffsetPtrs[&I] = BaseAndOffset;
-
-      // Also handle SROA candidates here, we already know that the GEP is
-      // all-constant indexed.
-      if (SROACandidate)
-        SROAArgValues[&I] = SROAArg;
-
-      return true;
-    }
-  }
-
   // Lambda to check whether a GEP's indices are all constant.
   auto IsGEPOffsetConstant = [&](GetElementPtrInst &GEP) {
     for (User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end(); I != E; ++I)
@@ -473,7 +468,7 @@ bool CallAnalyzer::visitGetElementPtr(GetElementPtrInst &I) {
     return true;
   };
 
-  if (IsGEPOffsetConstant(I)) {
+  if ((I.isInBounds() && canFoldInboundsGEP(I)) || IsGEPOffsetConstant(I)) {
     if (SROACandidate)
       SROAArgValues[&I] = SROAArg;
 
-- 
2.11.0