From 055097f0249a08a78b7acc3c047e265dec11c0c9 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Sun, 27 Jun 2010 06:26:04 +0000
Subject: If coercing something from int or pointer type to int or pointer type
 (potentially after unwrapping it from a struct) do it without going through
 memory.  We now compile:

struct DeclGroup {
  unsigned NumDecls;
};

int foo(DeclGroup D) {
  return D.NumDecls;
}

into:

%struct.DeclGroup = type { i32 }

define i32 @_Z3foo9DeclGroup(i64) nounwind ssp noredzone {
entry:
  %D = alloca %struct.DeclGroup, align 4          ; <%struct.DeclGroup*> [#uses=2]
  %coerce.dive = getelementptr %struct.DeclGroup* %D, i32 0, i32 0 ; <i32*> [#uses=1]
  %coerce.val.ii = trunc i64 %0 to i32            ; <i32> [#uses=1]
  store i32 %coerce.val.ii, i32* %coerce.dive
  %tmp = getelementptr inbounds %struct.DeclGroup* %D, i32 0, i32 0 ; <i32*> [#uses=1]
  %tmp1 = load i32* %tmp                          ; <i32> [#uses=1]
  ret i32 %tmp1
}

instead of:

%struct.DeclGroup = type { i32 }

define i32 @_Z3foo9DeclGroup(i64) nounwind ssp noredzone {
entry:
  %D = alloca %struct.DeclGroup, align 4          ; <%struct.DeclGroup*> [#uses=2]
  %tmp = alloca i64                               ; <i64*> [#uses=2]
  %coerce.dive = getelementptr %struct.DeclGroup* %D, i32 0, i32 0 ; <i32*> [#uses=1]
  store i64 %0, i64* %tmp
  %1 = bitcast i64* %tmp to i32*                  ; <i32*> [#uses=1]
  %2 = load i32* %1, align 1                      ; <i32> [#uses=1]
  store i32 %2, i32* %coerce.dive
  %tmp1 = getelementptr inbounds %struct.DeclGroup* %D, i32 0, i32 0 ; <i32*> [#uses=1]
  %tmp2 = load i32* %tmp1                         ; <i32> [#uses=1]
  ret i32 %tmp2
}

... which is quite a bit less terrifying.

llvm-svn: 106975
---
 clang/lib/CodeGen/CGCall.cpp | 49 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

(limited to 'clang/lib/CodeGen/CGCall.cpp')

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 7835505dcf4..6151fa2ed4c 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -378,6 +378,38 @@ EnterStructPointerForCoercedAccess(llvm::Value *SrcPtr,
   return SrcPtr;
 }
 
+/// CoerceIntOrPtrToIntOrPtr - Convert a value Val to the specific Ty where both
+/// are either integers or pointers.  This does a truncation of the value if it
+/// is too large or a zero extension if it is too small.
+static llvm::Value *CoerceIntOrPtrToIntOrPtr(llvm::Value *Val,
+                                             const llvm::Type *Ty,
+                                             CodeGenFunction &CGF) {
+  if (Val->getType() == Ty)
+    return Val;
+  
+  if (isa<llvm::PointerType>(Val->getType())) {
+    // If this is Pointer->Pointer avoid conversion to and from int.
+    if (isa<llvm::PointerType>(Ty))
+      return CGF.Builder.CreateBitCast(Val, Ty, "coerce.val");
+  
+    // Convert the pointer to an integer so we can play with its width.
+    const llvm::Type *IntPtrTy = llvm::IntegerType::get(Ty->getContext(),
+                                                        CGF.LLVMPointerWidth);
+    Val = CGF.Builder.CreatePtrToInt(Val, IntPtrTy, "coerce.val.pi");
+  }
+  
+  const llvm::Type *DestIntTy = Ty;
+  if (isa<llvm::PointerType>(DestIntTy))
+    DestIntTy = llvm::IntegerType::get(Ty->getContext(), CGF.LLVMPointerWidth);
+  
+  if (Val->getType() != DestIntTy)
+    Val = CGF.Builder.CreateIntCast(Val, DestIntTy, false, "coerce.val.ii");
+  
+  if (isa<llvm::PointerType>(Ty))
+    Val = CGF.Builder.CreateIntToPtr(Val, Ty, "coerce.val.ip");
+  return Val;
+}
+
 
 
 /// CreateCoercedLoad - Create a load from \arg SrcPtr interpreted as
@@ -400,6 +432,14 @@ static llvm::Value *CreateCoercedLoad(llvm::Value *SrcPtr,
   
   uint64_t SrcSize = CGF.CGM.getTargetData().getTypeAllocSize(SrcTy);
 
+  // If the source and destination are integer or pointer types, just do an
+  // extension or truncation to the desired type.
+  if ((isa<llvm::IntegerType>(Ty) || isa<llvm::PointerType>(Ty)) &&
+      (isa<llvm::IntegerType>(SrcTy) || isa<llvm::PointerType>(SrcTy))) {
+    llvm::LoadInst *Load = CGF.Builder.CreateLoad(SrcPtr);
+    return CoerceIntOrPtrToIntOrPtr(Load, Ty, CGF);
+  }
+  
   // If load is legal, just bitcast the src pointer.
   if (SrcSize >= DstSize) {
     // Generally SrcSize is never greater than DstSize, since this means we are
@@ -448,6 +488,15 @@ static void CreateCoercedStore(llvm::Value *Src,
     DstTy = cast<llvm::PointerType>(DstPtr->getType())->getElementType();
   }
   
+  // If the source and destination are integer or pointer types, just do an
+  // extension or truncation to the desired type.
+  if ((isa<llvm::IntegerType>(SrcTy) || isa<llvm::PointerType>(SrcTy)) &&
+      (isa<llvm::IntegerType>(DstTy) || isa<llvm::PointerType>(DstTy))) {
+    Src = CoerceIntOrPtrToIntOrPtr(Src, DstTy, CGF);
+    CGF.Builder.CreateStore(Src, DstPtr, DstIsVolatile);
+    return;
+  }
+  
   uint64_t DstSize = CGF.CGM.getTargetData().getTypeAllocSize(DstTy);
 
   // If store is legal, just bitcast the src pointer.
-- 
cgit v1.2.3