[Inliner] Preserve alignment of byval arguments (llvm#137455)

Previously the inliner always produced a memcpy with alignment 1 for src
and destination, leading to potentially suboptimal Codegen.

Since the Src ptr alignment is only available through the CallBase it
has to be passed to HandleByValArgumentInit. Dst Alignment is already
known so it doesn't have to be passed along.

If there is no specified Src Alignment my changes cause the ptr to have
no align data attached instead of align 1 as before (see
inline-tail.ll), I believe this is fine but since I'm a first time
contributor, please confirm.

My changes are already covered by 4 existing regression tests, so I did
not add any additional ones.

The example from llvm#45778 now results in:
```C
opt -S -passes=inline,instcombine,sroa,instcombine test.ll

define dso_local i32 @test(ptr %t) {
entry:
  %.sroa.0.0.copyload = load ptr, ptr %t, align 8       # this used to be align 1 in the original issue
  %arrayidx.i = getelementptr inbounds nuw i8, ptr %.sroa.0.0.copyload, i64 24
  %0 = load i32, ptr %arrayidx.i, align 4
  ret i32 %0
}
```

Fixes llvm#45778.

Author: sallto

llvm/lib/Transforms/Utils/InlineFunction.cpp

@@ -1703,19 +1703,19 @@ static void AddAlignmentAssumptions(CallBase &CB, InlineFunctionInfo &IFI) {
 }
 
 static void HandleByValArgumentInit(Type *ByValType, Value *Dst, Value *Src,
-                                    Module *M, BasicBlock *InsertBlock,
+                                    MaybeAlign SrcAlign, Module *M,
+                                    BasicBlock *InsertBlock,
                                     InlineFunctionInfo &IFI,
                                     Function *CalledFunc) {
   IRBuilder<> Builder(InsertBlock, InsertBlock->begin());
 
   Value *Size =
       Builder.getInt64(M->getDataLayout().getTypeStoreSize(ByValType));
 
-  // Always generate a memcpy of alignment 1 here because we don't know
-  // the alignment of the src pointer.  Other optimizations can infer
-  // better alignment.
-  CallInst *CI = Builder.CreateMemCpy(Dst, /*DstAlign*/ Align(1), Src,
-                                      /*SrcAlign*/ Align(1), Size);
+  Align DstAlign = Dst->getPointerAlignment(M->getDataLayout());
+
+  // Generate a memcpy with the correct alignments.
+  CallInst *CI = Builder.CreateMemCpy(Dst, DstAlign, Src, SrcAlign, Size);
 
   // The verifier requires that all calls of debug-info-bearing functions
   // from debug-info-bearing functions have a debug location (for inlining
@@ -2629,9 +2629,12 @@ llvm::InlineResult llvm::InlineFunction(CallBase &CB, InlineFunctionInfo &IFI,
     struct ByValInit {
       Value *Dst;
       Value *Src;
+      MaybeAlign SrcAlign;
       Type *Ty;
     };
-    // Keep a list of pair (dst, src) to emit byval initializations.
+    // Keep a list of tuples (dst, src, src_align) to emit byval
+    // initializations. Src Alignment is only available though the callbase,
+    // therefore has to be saved.
     SmallVector<ByValInit, 4> ByValInits;
 
     // When inlining a function that contains noalias scope metadata,
@@ -2661,8 +2664,9 @@ llvm::InlineResult llvm::InlineFunction(CallBase &CB, InlineFunctionInfo &IFI,
                                         &CB, CalledFunc, IFI,
                                         CalledFunc->getParamAlign(ArgNo));
         if (ActualArg != *AI)
-          ByValInits.push_back(
-              {ActualArg, (Value *)*AI, CB.getParamByValType(ArgNo)});
+          ByValInits.push_back({ActualArg, (Value *)*AI,
+                                CB.getParamAlign(ArgNo),
+                                CB.getParamByValType(ArgNo)});
       }
 
       VMap[&*I] = ActualArg;
@@ -2712,8 +2716,9 @@ llvm::InlineResult llvm::InlineFunction(CallBase &CB, InlineFunctionInfo &IFI,
 
     // Inject byval arguments initialization.
     for (ByValInit &Init : ByValInits)
-      HandleByValArgumentInit(Init.Ty, Init.Dst, Init.Src, Caller->getParent(),
-                              &*FirstNewBlock, IFI, CalledFunc);
+      HandleByValArgumentInit(Init.Ty, Init.Dst, Init.Src, Init.SrcAlign,
+                              Caller->getParent(), &*FirstNewBlock, IFI,
+                              CalledFunc);
 
     std::optional<OperandBundleUse> ParentDeopt =
         CB.getOperandBundle(LLVMContext::OB_deopt);

llvm/test/Transforms/Inline/byval-align.ll

@@ -29,7 +29,7 @@ define void @byval_caller(ptr nocapture align 64 %a, ptr %b) #0 {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[A1:%.*]] = alloca float, align 128
 ; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 4, ptr [[A1]])
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[A1]], ptr align 1 [[A]], i64 4, i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 128 [[A1]], ptr align 128 [[A]], i64 4, i1 false)
 ; CHECK-NEXT:    [[LOAD_I:%.*]] = load float, ptr [[A1]], align 4
 ; CHECK-NEXT:    [[B_IDX_I:%.*]] = getelementptr inbounds float, ptr [[B]], i64 8
 ; CHECK-NEXT:    [[ADD_I:%.*]] = fadd float [[LOAD_I]], 2.000000e+00

llvm/test/Transforms/Inline/byval-with-non-alloca-addrspace.ll

@@ -27,7 +27,7 @@ define i64 @foo(ptr %arg) {
 ; CHECK-SAME: ptr [[ARG:%.*]]) {
 ; CHECK-NEXT:    [[ARG1:%.*]] = alloca [[STRUCT:%.*]], align 8
 ; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 16, ptr [[ARG1]])
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[ARG1]], ptr align 1 [[ARG]], i64 16, i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 8 [[ARG1]], ptr align 8 [[ARG]], i64 16, i1 false)
 ; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr [[STRUCT]], ptr [[ARG1]], i64 0, i32 1
 ; CHECK-NEXT:    [[TMP2:%.*]] = load i64, ptr [[TMP1]], align 4
 ; CHECK-NEXT:    call void @llvm.lifetime.end.p0(i64 16, ptr [[ARG1]])

llvm/test/Transforms/Inline/byval.ll

@@ -36,7 +36,7 @@ define i32 @test1() nounwind  {
 ; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr [[STRUCT_SS]], ptr [[S]], i32 0, i32 1
 ; CHECK-NEXT:    store i64 2, ptr [[TMP4]], align 4
 ; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 12, ptr [[S1]])
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[S1]], ptr align 1 [[S]], i64 12, i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 8 [[S1]], ptr [[S]], i64 12, i1 false)
 ; CHECK-NEXT:    [[TMP1_I:%.*]] = load i32, ptr [[S1]], align 4
 ; CHECK-NEXT:    [[TMP2_I:%.*]] = add i32 [[TMP1_I]], 1
 ; CHECK-NEXT:    store i32 [[TMP2_I]], ptr [[S1]], align 4
@@ -105,7 +105,7 @@ define void @test3() nounwind  {
 ; CHECK-NEXT:    [[S1:%.*]] = alloca [[STRUCT_SS:%.*]], align 64
 ; CHECK-NEXT:    [[S:%.*]] = alloca [[STRUCT_SS]], align 1
 ; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 12, ptr [[S1]])
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[S1]], ptr align 1 [[S]], i64 12, i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 64 [[S1]], ptr align 64 [[S]], i64 12, i1 false)
 ; CHECK-NEXT:    call void @g3(ptr align 64 [[S1]]) #[[ATTR0]]
 ; CHECK-NEXT:    call void @llvm.lifetime.end.p0(i64 12, ptr [[S1]])
 ; CHECK-NEXT:    ret void
@@ -158,7 +158,7 @@ define i32 @test5() {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[B:%.*]] = alloca [[STRUCT_S0:%.*]], align 8
 ; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 4, ptr [[B]])
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[B]], ptr align 1 @b, i64 4, i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 8 [[B]], ptr align 4 @b, i64 4, i1 false)
 ; CHECK-NEXT:    store i32 0, ptr @b, align 4
 ; CHECK-NEXT:    [[TMP0:%.*]] = load i32, ptr [[B]], align 4
 ; CHECK-NEXT:    store i32 [[TMP0]], ptr @a, align 4

llvm/test/Transforms/Inline/inline-deferred-instsimplify.ll

@@ -53,7 +53,7 @@ define i32 @main() {
 ; CHECK-LABEL: define i32 @main() {
 ; CHECK-NEXT:    [[G_VAR:%.*]] = alloca [[STRUCT_A:%.*]], align 8
 ; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 20, ptr [[G_VAR]])
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[G_VAR]], ptr align 1 @g_var, i64 20, i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 8 [[G_VAR]], ptr align 8 @g_var, i64 20, i1 false)
 ; CHECK-NEXT:    [[VAL_I:%.*]] = load i32, ptr [[G_VAR]], align 8
 ; CHECK-NEXT:    [[DOTNOT_I:%.*]] = icmp eq i32 [[VAL_I]], 0
 ; CHECK-NEXT:    br i1 [[DOTNOT_I]], label [[CHECK_POINTERS_ARE_EQUAL_I:%.*]], label [[STORE_PTR_IN_GVAR_I:%.*]]

llvm/test/Transforms/Inline/inline-tail.ll

@@ -65,7 +65,7 @@ define void @test_byval_a(ptr byval(i32) %p) {
 ; CHECK-SAME: (ptr byval(i32) [[P:%.*]]) {
 ; CHECK-NEXT:    [[P1:%.*]] = alloca i32, align 4
 ; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 4, ptr [[P1]])
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[P1]], ptr align 1 [[P]], i64 4, i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 4 [[P1]], ptr [[P]], i64 4, i1 false)
 ; CHECK-NEXT:    musttail call void @test_byval_c(ptr byval(i32) [[P1]])
 ; CHECK-NEXT:    ret void
 ;
@@ -88,7 +88,7 @@ define void @test_dynalloca_a(ptr byval(i32) %p, i32 %n) {
 ; CHECK-NEXT:    [[P1:%.*]] = alloca i32, align 4
 ; CHECK-NEXT:    [[SAVEDSTACK:%.*]] = call ptr @llvm.stacksave.p0()
 ; CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 4, ptr [[P1]])
-; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[P1]], ptr align 1 [[P]], i64 4, i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 4 [[P1]], ptr [[P]], i64 4, i1 false)
 ; CHECK-NEXT:    [[BUF_I:%.*]] = alloca i8, i32 [[N]], align 1
 ; CHECK-NEXT:    call void @escape(ptr [[BUF_I]])
 ; CHECK-NEXT:    musttail call void @test_dynalloca_c(ptr byval(i32) [[P1]], i32 [[N]])