Bitcasts are transitive. Bitcast-Bitcast-X becomes Bitcast-X.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138722 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index df79849..613804d 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -51,6 +51,12 @@
if (C->isAllOnesValue() && !DestTy->isX86_MMXTy())
return Constant::getAllOnesValue(DestTy);
+ // Bitcast of Bitcast can be done using a single cast.
+ ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
+ if (CE && CE->getOpcode() == Instruction::BitCast) {
+ return ConstantExpr::getBitCast(CE->getOperand(0), DestTy);
+ }
+
// The code below only handles casts to vectors currently.
VectorType *DestVTy = dyn_cast<VectorType>(DestTy);
if (DestVTy == 0)
diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index ba90bf6..6c42c0c 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1659,6 +1659,11 @@
if (DestTy == Src->getType())
return ReplaceInstUsesWith(CI, Src);
+ // Bitcasts are transitive.
+ if (BitCastInst* BSrc = dyn_cast<BitCastInst>(Src)) {
+ return CastInst::Create(Instruction::BitCast, BSrc->getOperand(0), DestTy);
+ }
+
if (PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) {
PointerType *SrcPTy = cast<PointerType>(SrcTy);
Type *DstElTy = DstPTy->getElementType();
diff --git a/test/Transforms/InstCombine/cast.ll b/test/Transforms/InstCombine/cast.ll
index f85636f..06cdae2 100644
--- a/test/Transforms/InstCombine/cast.ll
+++ b/test/Transforms/InstCombine/cast.ll
@@ -630,3 +630,17 @@
; CHECK: uitofp
}
+define <4 x float> @test64(<4 x float> %c) nounwind {
+ %t0 = bitcast <4 x float> %c to <4 x i32>
+ %t1 = bitcast <4 x i32> %t0 to <2 x double>
+ %t2 = bitcast <2 x double> %t1 to <4 x float>
+ ret <4 x float> %t2
+; CHECK: @test64
+; CHECK-NEXT: ret <4 x float> %c
+}
+
+define float @test2c() {
+ ret float extractelement (<2 x float> bitcast (double bitcast (<2 x float> <float -1.000000e+00, float -1.000000e+00> to double) to <2 x float>), i32 0)
+; CHECK: @test2c
+; CHECK-NOT: extractelement
+}
