Fix previous commit: [FastISel][AArch64] Simplify XALU multiplies.

When folding the intrinsic flag into the branch or select we also have to
consider the fact if the intrinsic got simplified, because it changes the
flag we have to check for.

llvm-svn: 218034

1 files changed, 42 insertions, 8 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64FastISel.cpp b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
index e64f1bdacd8..88038ff0844 100644
--- a/llvm/lib/Target/AArch64/AArch64FastISel.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FastISel.cpp
@@ -2833,15 +2833,49 @@ bool AArch64FastISel::foldXALUIntrinsic(AArch64CC::CondCode &CC,
   if (RetVT != MVT::i32 && RetVT != MVT::i64)
     return false;
 
+  const Value *LHS = II->getArgOperand(0);
+  const Value *RHS = II->getArgOperand(1);
+
+  // Canonicalize immediate to the RHS.
+  if (isa<ConstantInt>(LHS) && !isa<ConstantInt>(RHS) &&
+      isCommutativeIntrinsic(II))
+    std::swap(LHS, RHS);
+
+  // Simplify multiplies.
+  unsigned IID = II->getIntrinsicID();
+  switch (IID) {
+  default:
+    break;
+  case Intrinsic::smul_with_overflow:
+    if (const auto *C = dyn_cast<ConstantInt>(RHS))
+      if (C->getValue() == 2)
+        IID = Intrinsic::sadd_with_overflow;
+    break;
+  case Intrinsic::umul_with_overflow:
+    if (const auto *C = dyn_cast<ConstantInt>(RHS))
+      if (C->getValue() == 2)
+        IID = Intrinsic::uadd_with_overflow;
+    break;
+  }
+
   AArch64CC::CondCode TmpCC;
-  switch (II->getIntrinsicID()) {
-    default: return false;
-    case Intrinsic::sadd_with_overflow:
-    case Intrinsic::ssub_with_overflow: TmpCC = AArch64CC::VS; break;
-    case Intrinsic::uadd_with_overflow: TmpCC = AArch64CC::HS; break;
-    case Intrinsic::usub_with_overflow: TmpCC = AArch64CC::LO; break;
-    case Intrinsic::smul_with_overflow:
-    case Intrinsic::umul_with_overflow: TmpCC = AArch64CC::NE; break;
+  switch (IID) {
+  default:
+    return false;
+  case Intrinsic::sadd_with_overflow:
+  case Intrinsic::ssub_with_overflow:
+    TmpCC = AArch64CC::VS;
+    break;
+  case Intrinsic::uadd_with_overflow:
+    TmpCC = AArch64CC::HS;
+    break;
+  case Intrinsic::usub_with_overflow:
+    TmpCC = AArch64CC::LO;
+    break;
+  case Intrinsic::smul_with_overflow:
+  case Intrinsic::umul_with_overflow:
+    TmpCC = AArch64CC::NE;
+    break;
   }
 
   // Check if both instructions are in the same basic block.