[Alignment][NFC] Convert MachineIRBuilder::buildDynStackAlloc to Align

Summary:
The change in IRTranslator is not trivial but is NFC as far as I can tell.

This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

Reviewers: courbet

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D77292

llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h

@@ -379,7 +379,14 @@ public:
   ///
   /// \return a MachineInstrBuilder for the newly created instruction.
   MachineInstrBuilder buildDynStackAlloc(const DstOp &Res, const SrcOp &Size,
-                                         unsigned Align);
+                                         Align Alignment);
+
+  LLVM_ATTRIBUTE_DEPRECATED(inline MachineInstrBuilder buildDynStackAlloc(
+                                const DstOp &Res, const SrcOp &Size,
+                                unsigned Align),
+                            "Use the version that takes MaybeAlign instead") {
+    return buildDynStackAlloc(Res, Size, assumeAligned(Align));
+  }
 
   /// Build and insert \p Res = G_FRAME_INDEX \p Idx
   ///

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -1859,7 +1859,6 @@ bool IRTranslator::translateAlloca(const User &U,
 
   // Now we're in the harder dynamic case.
   Register NumElts = getOrCreateVReg(*AI.getArraySize());
-
   Type *IntPtrIRTy = DL->getIntPtrType(AI.getType());
   LLT IntPtrTy = getLLTForType(*IntPtrIRTy, *DL);
   if (MRI->getType(NumElts) != IntPtrTy) {
@@ -1878,22 +1877,20 @@ bool IRTranslator::translateAlloca(const User &U,
   // Round the size of the allocation up to the stack alignment size
   // by add SA-1 to the size. This doesn't overflow because we're computing
   // an address inside an alloca.
-  unsigned StackAlign =
+  Align StackAlign = MF->getSubtarget().getFrameLowering()->getStackAlign();
-      MF->getSubtarget().getFrameLowering()->getStackAlignment();
+  auto SAMinusOne = MIRBuilder.buildConstant(IntPtrTy, StackAlign.value() - 1);
-  auto SAMinusOne = MIRBuilder.buildConstant(IntPtrTy, StackAlign - 1);
   auto AllocAdd = MIRBuilder.buildAdd(IntPtrTy, AllocSize, SAMinusOne,
                                       MachineInstr::NoUWrap);
   auto AlignCst =
-      MIRBuilder.buildConstant(IntPtrTy, ~(uint64_t)(StackAlign - 1));
+      MIRBuilder.buildConstant(IntPtrTy, ~(uint64_t)(StackAlign.value() - 1));
   auto AlignedAlloc = MIRBuilder.buildAnd(IntPtrTy, AllocAdd, AlignCst);
 
-  unsigned Align =
+  Align Alignment = max(AI.getAlign(), DL->getPrefTypeAlign(Ty));
-      std::max((unsigned)DL->getPrefTypeAlignment(Ty), AI.getAlignment());
+  if (Alignment <= StackAlign)
-  if (Align <= StackAlign)
+    Alignment = Align(1);
-    Align = 0;
+  MIRBuilder.buildDynStackAlloc(getOrCreateVReg(AI), AlignedAlloc, Alignment);
-  MIRBuilder.buildDynStackAlloc(getOrCreateVReg(AI), AlignedAlloc, Align);
 
-  MF->getFrameInfo().CreateVariableSizedObject(Align ? Align : 1, &AI);
+  MF->getFrameInfo().CreateVariableSizedObject(Alignment, &AI);
   assert(MF->getFrameInfo().hasVarSizedObjects());
   return true;
 }

llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp

@@ -162,12 +162,12 @@ MachineInstrBuilder MachineIRBuilder::buildDbgLabel(const MDNode *Label) {
 
 MachineInstrBuilder MachineIRBuilder::buildDynStackAlloc(const DstOp &Res,
                                                          const SrcOp &Size,
-                                                         unsigned Align) {
+                                                         Align Alignment) {
   assert(Res.getLLTTy(*getMRI()).isPointer() && "expected ptr dst type");
   auto MIB = buildInstr(TargetOpcode::G_DYN_STACKALLOC);
   Res.addDefToMIB(*getMRI(), MIB);
   Size.addSrcToMIB(MIB);
-  MIB.addImm(Align);
+  MIB.addImm(Alignment.value());
   return MIB;
 }
 

llvm/test/CodeGen/AArch64/GlobalISel/dynamic-alloca.ll

@@ -13,7 +13,7 @@ define i8* @test_simple_alloca(i32 %numelts) {
   ; CHECK:   [[ADD:%[0-9]+]]:_(s64) = nuw G_ADD [[MUL]], [[C1]]
   ; CHECK:   [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 -16
   ; CHECK:   [[AND:%[0-9]+]]:_(s64) = G_AND [[ADD]], [[C2]]
-  ; CHECK:   [[DYN_STACKALLOC:%[0-9]+]]:_(p0) = G_DYN_STACKALLOC [[AND]](s64), 0
+  ; CHECK:   [[DYN_STACKALLOC:%[0-9]+]]:_(p0) = G_DYN_STACKALLOC [[AND]](s64), 1
   ; CHECK:   $x0 = COPY [[DYN_STACKALLOC]](p0)
   ; CHECK:   RET_ReallyLR implicit $x0
   %addr = alloca i8, i32 %numelts
@@ -51,7 +51,7 @@ define i128* @test_natural_alloca(i32 %numelts) {
   ; CHECK:   [[ADD:%[0-9]+]]:_(s64) = nuw G_ADD [[MUL]], [[C1]]
   ; CHECK:   [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 -16
   ; CHECK:   [[AND:%[0-9]+]]:_(s64) = G_AND [[ADD]], [[C2]]
-  ; CHECK:   [[DYN_STACKALLOC:%[0-9]+]]:_(p0) = G_DYN_STACKALLOC [[AND]](s64), 0
+  ; CHECK:   [[DYN_STACKALLOC:%[0-9]+]]:_(p0) = G_DYN_STACKALLOC [[AND]](s64), 1
   ; CHECK:   $x0 = COPY [[DYN_STACKALLOC]](p0)
   ; CHECK:   RET_ReallyLR implicit $x0
   %addr = alloca i128, i32 %numelts