It turns out most of the thumb2 instructions are not allowed to touch SP. The semantics of such instructions are unpredictable. We have just been lucky that tests have been passing.

This patch takes pain to ensure all the PEI lowering code does the right thing when lowering frame indices, insert code to manipulate stack pointers, etc. It's also custom lowering dynamic stack alloc into pseudo instructions so we can insert the right instructions at scheduling time.

This fixes PR4659 and PR4682.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78361 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 57 insertions, 19 deletions

diff --git a/lib/Target/ARM/ARMISelDAGToDAG.cpp b/lib/Target/ARM/ARMISelDAGToDAG.cpp
index d996b24..04f4dd3 100644
--- a/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -122,6 +122,8 @@ private:
   SDNode *SelectARMIndexedLoad(SDValue Op);
   SDNode *SelectT2IndexedLoad(SDValue Op);
 
+  /// SelectDYN_ALLOC - Select dynamic alloc for Thumb.
+  SDNode *SelectDYN_ALLOC(SDValue Op);
 
   /// SelectInlineAsmMemoryOperand - Implement addressing mode selection for
   /// inline asm expressions.
@@ -868,6 +870,59 @@ SDNode *ARMDAGToDAGISel::SelectT2IndexedLoad(SDValue Op) {
   return NULL;
 }
 
+SDNode *ARMDAGToDAGISel::SelectDYN_ALLOC(SDValue Op) {
+  SDNode *N = Op.getNode();
+  DebugLoc dl = N->getDebugLoc();
+  MVT VT = Op.getValueType();
+  SDValue Chain = Op.getOperand(0);
+  SDValue Size = Op.getOperand(1);
+  SDValue Align = Op.getOperand(2);
+  SDValue SP = CurDAG->getRegister(ARM::SP, MVT::i32);
+  int32_t AlignVal = cast<ConstantSDNode>(Align)->getSExtValue();
+  if (AlignVal < 0)
+    // We need to align the stack. Use Thumb1 tAND which is the only thumb
+    // instruction that can read and write SP. This matches to a pseudo
+    // instruction that has a chain to ensure the result is written back to
+    // the stack pointer.
+    SP = SDValue(CurDAG->getTargetNode(ARM::tANDsp, dl, VT, SP, Align), 0);
+
+  bool isC = isa<ConstantSDNode>(Size);
+  uint32_t C = isC ? cast<ConstantSDNode>(Size)->getZExtValue() : ~0UL;
+  // Handle the most common case for both Thumb1 and Thumb2:
+  // tSUBspi - immediate is between 0 ... 508 inclusive.
+  if (C <= 508 && ((C & 3) == 0))
+    // FIXME: tSUBspi encode scale 4 implicitly.
+    return CurDAG->SelectNodeTo(N, ARM::tSUBspi_, VT, MVT::Other, SP,
+                                CurDAG->getTargetConstant(C/4, MVT::i32),
+                                Chain);
+
+  if (Subtarget->isThumb1Only()) {
+    // Use tADDrSPr since Thumb1 does not have a sub r, sp, r. ARMISelLowering
+    // should have negated the size operand already. FIXME: We can't insert
+    // new target independent node at this stage so we are forced to negate
+    // it earlier. Is there a better solution? 
+    return CurDAG->SelectNodeTo(N, ARM::tADDspr_, VT, MVT::Other, SP, Size,
+                                Chain);
+  } else if (Subtarget->isThumb2()) {
+    if (isC && Predicate_t2_so_imm(Size.getNode())) {
+      // t2SUBrSPi
+      SDValue Ops[] = { SP, CurDAG->getTargetConstant(C, MVT::i32), Chain };
+      return CurDAG->SelectNodeTo(N, ARM::t2SUBrSPi_, VT, MVT::Other, Ops, 3);
+    } else if (isC && Predicate_imm0_4095(Size.getNode())) {
+      // t2SUBrSPi12
+      SDValue Ops[] = { SP, CurDAG->getTargetConstant(C, MVT::i32), Chain };
+      return CurDAG->SelectNodeTo(N, ARM::t2SUBrSPi12_, VT, MVT::Other, Ops, 3);
+    } else {
+      // t2SUBrSPs
+      SDValue Ops[] = { SP, Size,
+                        getI32Imm(ARM_AM::getSORegOpc(ARM_AM::lsl,0)), Chain };
+      return CurDAG->SelectNodeTo(N, ARM::t2SUBrSPs_, VT, MVT::Other, Ops, 4);
+    }
+  }
+
+  // FIXME: Add ADD / SUB sp instructions for ARM.
+  return 0;
+}
 
 SDNode *ARMDAGToDAGISel::Select(SDValue Op) {
   SDNode *N = Op.getNode();
@@ -941,25 +996,8 @@ SDNode *ARMDAGToDAGISel::Select(SDValue Op) {
       return CurDAG->SelectNodeTo(N, Opc, MVT::i32, Ops, 5);
     }
   }
-  case ISD::ADD: {
-    if (!Subtarget->isThumb1Only())
-      break;
-    // Select add sp, c to tADDhirr.
-    SDValue N0 = Op.getOperand(0);
-    SDValue N1 = Op.getOperand(1);
-    RegisterSDNode *LHSR = dyn_cast<RegisterSDNode>(Op.getOperand(0));
-    RegisterSDNode *RHSR = dyn_cast<RegisterSDNode>(Op.getOperand(1));
-    if (LHSR && LHSR->getReg() == ARM::SP) {
-      std::swap(N0, N1);
-      std::swap(LHSR, RHSR);
-    }
-    if (RHSR && RHSR->getReg() == ARM::SP) {
-      SDValue Val = SDValue(CurDAG->getTargetNode(ARM::tMOVtgpr2gpr, dl,
-                                                  Op.getValueType(), N0, N0),0);
-      return CurDAG->SelectNodeTo(N, ARM::tADDhirr, Op.getValueType(), Val, N1);
-    }
-    break;
-  }
+  case ARMISD::DYN_ALLOC:
+    return SelectDYN_ALLOC(Op);
   case ISD::MUL:
     if (Subtarget->isThumb1Only())
       break;