[FastISel][AArch64] Don't bail during simple GEP instruction selection.

The generic FastISel code would bail, because it can't emit a sign-extend for
AArch64. This copies the code over and uses AArch64 specific emit functions.

This is not ideal and 'computeAddress' should handles this, so it can fold the
address computation into the memory operation.

I plan to clean up 'computeAddress' anyways, so I will add that in a future
commit.

Related to rdar://problem/18962471.

llvm-svn: 221923

1 files changed, 23 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64FastISel.cpp b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
index 1b1aaf214fb..4d18a4e0b0f 100644
--- a/llvm/lib/Target/AArch64/AArch64FastISel.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
@@ -151,6 +151,7 @@ private:
                          const Value *Cond);
   bool optimizeIntExtLoad(const Instruction *I, MVT RetVT, MVT SrcVT);
   bool optimizeSelect(const SelectInst *SI);
+  std::pair<unsigned, bool> getRegForGEPIndex(const Value *Idx);
 
   // Emit helper routines.
   unsigned emitAddSub(bool UseAdd, MVT RetVT, const Value *LHS,
@@ -4725,6 +4726,28 @@ bool AArch64FastISel::selectSDiv(const Instruction *I) {
   return true;
 }
 
+/// This is mostly a copy of the existing FastISel getRegForGEPIndex code. We
+/// have to duplicate it for AArch64, because otherwise we would fail during the
+/// sign-extend emission.
+std::pair<unsigned, bool> AArch64FastISel::getRegForGEPIndex(const Value *Idx) {
+  unsigned IdxN = getRegForValue(Idx);
+  if (IdxN == 0)
+    // Unhandled operand. Halt "fast" selection and bail.
+    return std::pair<unsigned, bool>(0, false);
+
+  bool IdxNIsKill = hasTrivialKill(Idx);
+
+  // If the index is smaller or larger than intptr_t, truncate or extend it.
+  MVT PtrVT = TLI.getPointerTy();
+  EVT IdxVT = EVT::getEVT(Idx->getType(), /*HandleUnknown=*/false);
+  if (IdxVT.bitsLT(PtrVT)) {
+    IdxN = emitIntExt(IdxVT.getSimpleVT(), IdxN, PtrVT, /*IsZExt=*/false);
+    IdxNIsKill = true;
+  } else if (IdxVT.bitsGT(PtrVT))
+    llvm_unreachable("AArch64 FastISel doesn't support types larger than i64");
+  return std::pair<unsigned, bool>(IdxN, IdxNIsKill);
+}
+
 /// This is mostly a copy of the existing FastISel GEP code, but we have to
 /// duplicate it for AArch64, because otherwise we would bail out even for
 /// simple cases. This is because the standard fastEmit functions don't cover