[AArch64][GlobalISel] CallLowering: Don't generate new copies each time we need

to store to a stack ___location for outgoing args.

During call arg lowering we shouldn't be modifying SP so cache the SP copy
vreg for subsequent uses.

Gives a 0.2% geomean code size improvement on CTMark.

Differential Revision: https://reviews.llvm.org/D77838

Author: aemerson

llvm/lib/Target/AArch64/AArch64CallLowering.cpp

@@ -133,7 +133,7 @@ struct OutgoingArgHandler : public CallLowering::ValueHandler {
                      int FPDiff = 0)
       : ValueHandler(MIRBuilder, MRI, AssignFn), MIB(MIB),
         AssignFnVarArg(AssignFnVarArg), IsTailCall(IsTailCall), FPDiff(FPDiff),
-        StackSize(0) {}
+        StackSize(0), SPReg(0) {}
 
   bool isIncomingArgumentHandler() const override { return false; }
 
@@ -151,7 +151,8 @@ struct OutgoingArgHandler : public CallLowering::ValueHandler {
       return FIReg.getReg(0);
     }
 
-    auto SPReg = MIRBuilder.buildCopy(p0, Register(AArch64::SP));
+    if (!SPReg)
+      SPReg = MIRBuilder.buildCopy(p0, Register(AArch64::SP)).getReg(0);
 
     auto OffsetReg = MIRBuilder.buildConstant(s64, Offset);
 
@@ -204,6 +205,9 @@ struct OutgoingArgHandler : public CallLowering::ValueHandler {
   /// callee's. Unused elsewhere.
   int FPDiff;
   uint64_t StackSize;
+
+  // Cache the SP register vreg if we need it more than once in this call site.
+  Register SPReg;
 };
 } // namespace
 

llvm/test/CodeGen/AArch64/GlobalISel/call-translator-cse.ll

@@ -11,7 +11,6 @@
 ; CHECK: [[CST2:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
 ; CHECK: [[GEP2:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[CST2]](s64)
 ; CHECK: G_STORE [[LO]](s64), [[GEP2]](p0) :: (store 8 into stack, align 1)
-; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[GEP3:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[CST]](s64)
 ; CHECK: G_STORE [[HI]](s64), [[GEP3]](p0) :: (store 8 into stack + 8, align 1)
 define void @test_split_struct([2 x i64]* %ptr) {

llvm/test/CodeGen/AArch64/GlobalISel/call-translator-ios.ll

@@ -24,7 +24,6 @@ define signext i8 @test_stack_slots([8 x i64], i8 signext %lhs, i8 signext %rhs)
 ; CHECK: [[C42_OFFS:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
 ; CHECK: [[C42_LOC:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[C42_OFFS]](s64)
 ; CHECK: G_STORE [[C42]](s8), [[C42_LOC]](p0) :: (store 1 into stack)
-; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[C12_OFFS:%[0-9]+]]:_(s64) = G_CONSTANT i64 1
 ; CHECK: [[C12_LOC:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[C12_OFFS]](s64)
 ; CHECK: G_STORE [[C12]](s8), [[C12_LOC]](p0) :: (store 1 into stack + 1)
@@ -65,7 +64,6 @@ define void @take_128bit_struct([2 x i64]* %ptr, [2 x i64] %in) {
 ; CHECK: [[ADDR:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[OFF]](s64)
 ; CHECK: G_STORE [[LD1]](s64), [[ADDR]](p0) :: (store 8 into stack, align 1)
 
-; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[ADDR:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[CST]]
 ; CHECK: G_STORE [[LD2]](s64), [[ADDR]](p0) :: (store 8 into stack + 8, align 1)
 define void @test_split_struct([2 x i64]* %ptr) {

llvm/test/CodeGen/AArch64/GlobalISel/call-translator.ll

@@ -199,11 +199,9 @@ define void @test_stack_slots([8 x i64], i64 %lhs, i64 %rhs, i64* %addr) {
 ; CHECK: [[C42_OFFS:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
 ; CHECK: [[C42_LOC:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[C42_OFFS]](s64)
 ; CHECK: G_STORE [[C42]](s64), [[C42_LOC]](p0) :: (store 8 into stack, align 1)
-; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[C12_OFFS:%[0-9]+]]:_(s64) = G_CONSTANT i64 8
 ; CHECK: [[C12_LOC:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[C12_OFFS]](s64)
 ; CHECK: G_STORE [[C12]](s64), [[C12_LOC]](p0) :: (store 8 into stack + 8, align 1)
-; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[PTR_OFFS:%[0-9]+]]:_(s64) = G_CONSTANT i64 16
 ; CHECK: [[PTR_LOC:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[PTR_OFFS]](s64)
 ; CHECK: G_STORE [[PTR]](p0), [[PTR_LOC]](p0) :: (store 8 into stack + 16, align 1)
@@ -255,7 +253,6 @@ define void @take_128bit_struct([2 x i64]* %ptr, [2 x i64] %in) {
 ; CHECK: [[CST2:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
 ; CHECK: [[GEP2:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[CST2]](s64)
 ; CHECK: G_STORE [[LO]](s64), [[GEP2]](p0) :: (store 8 into stack, align 1)
-; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[GEP3:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[CST]](s64)
 ; CHECK: G_STORE [[HI]](s64), [[GEP3]](p0) :: (store 8 into stack + 8, align 1)
 define void @test_split_struct([2 x i64]* %ptr) {

llvm/test/CodeGen/AArch64/GlobalISel/irtranslator-exceptions.ll

@@ -71,7 +71,6 @@ continue:
 ; CHECK: [[ANSWER_EXT:%[0-9]+]]:_(s64) = G_ANYEXT [[ANSWER]]
 ; CHECK: G_STORE [[ANSWER_EXT]](s64), [[SLOT]]
 
-; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[OFFSET:%[0-9]+]]:_(s64) = G_CONSTANT i64 8
 ; CHECK: [[SLOT:%[0-9]+]]:_(p0) = G_PTR_ADD [[SP]], [[OFFSET]](s64)
 ; CHECK: G_STORE [[ONE]](s32), [[SLOT]]