enhance constant folding to be able to constant fold bitcast of

ConstantVector's to integer type.

llvm-svn: 149110

lib/Analysis/ConstantFolding.cpp

@@ -52,6 +52,44 @@ static Constant *FoldBitCast(Constant *C, Type *DestTy,
   if (C->isAllOnesValue() && !DestTy->isX86_MMXTy())
     return Constant::getAllOnesValue(DestTy);
 
+  // Handle a vector->integer cast.
+  if (IntegerType *IT = dyn_cast<IntegerType>(DestTy)) {
+    // FIXME: Remove ConstantVector support.
+    if ((!isa<ConstantDataVector>(C) && !isa<ConstantVector>(C)) ||
+        // TODO: Handle big endian someday.
+        !TD.isLittleEndian())
+      return ConstantExpr::getBitCast(C, DestTy);
+
+    unsigned NumSrcElts = C->getType()->getVectorNumElements();
+    
+    // If the vector is a vector of floating point, convert it to vector of int
+    // to simplify things.
+    if (C->getType()->getVectorElementType()->isFloatingPointTy()) {
+      unsigned FPWidth =
+        C->getType()->getVectorElementType()->getPrimitiveSizeInBits();
+      Type *SrcIVTy =
+        VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElts);
+      // Ask VMCore to do the conversion now that #elts line up.
+      C = ConstantExpr::getBitCast(C, SrcIVTy);
+    }
+    
+    // Now that we know that the input value is a vector of integers, just shift
+    // and insert them into our result.
+    unsigned BitShift =
+      TD.getTypeAllocSizeInBits(C->getType()->getVectorElementType());
+    APInt Result(IT->getBitWidth(), 0);
+    for (unsigned i = 0; i != NumSrcElts; ++i) {
+      // FIXME: Rework when we have ConstantDataVector.
+      ConstantInt *Elt=dyn_cast_or_null<ConstantInt>(C->getAggregateElement(i));
+      if (Elt == 0)  // Elt must be a constant expr or something.
+        return ConstantExpr::getBitCast(C, DestTy);
+      
+      Result |= Elt->getValue().zext(IT->getBitWidth()) << i*BitShift;
+    }
+   
+    return ConstantInt::get(IT, Result);
+  }
+  
   // The code below only handles casts to vectors currently.
   VectorType *DestVTy = dyn_cast<VectorType>(DestTy);
   if (DestVTy == 0)

test/Transforms/ConstProp/basictest.ll

@@ -1,5 +1,8 @@
 ; RUN: opt < %s -constprop -die -S | FileCheck %s
 
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.7.2"
+
 ; This is a basic sanity check for constant propagation.  The add instruction
 ; should be eliminated.
 define i32 @test1(i1 %B) {
@@ -40,3 +43,11 @@ define i1 @TNAN() {
   %C = or i1 %A, %B
   ret i1 %C
 }
+
+define i128 @vector_to_int_cast() {
+  %A = bitcast <4 x i32> <i32 1073741824, i32 1073741824, i32 1073741824, i32 1073741824> to i128
+  ret i128 %A
+; CHECK: @vector_to_int_cast
+; CHECK: ret i128 85070591750041656499021422275829170176
+}
+  

test/Transforms/InstCombine/icmp.ll

@@ -121,8 +121,8 @@ define i1 @test12(i1 %A) {
   %B = icmp ne i64 bitcast (<2 x i32> <i32 1, i32 -1> to i64), %S
   ret i1 %B
 ; CHECK: @test12
-; CHECK-NEXT: %B = select i1
-; CHECK-NEXT: ret i1 %B
+; CHECK-NEXT: = xor i1 %A, true
+; CHECK-NEXT: ret i1
 }
 
 ; PR6481