[DebugInfo] Maintain DI for sunken bitcasts

When a bitcast is being sunk in -codegenprepare pass, its DI wasn't
copied over to the newly created instruction. This patch fixes that
bug.

Patch by Kareem Ergawy!

Differential Revision: https://reviews.llvm.org/D47282

llvm-svn: 333133

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -1050,6 +1050,7 @@ static bool SinkCast(CastInst *CI) {
       assert(InsertPt != UserBB->end());
       InsertedCast = CastInst::Create(CI->getOpcode(), CI->getOperand(0),
                                       CI->getType(), "", &*InsertPt);
+      InsertedCast->setDebugLoc(CI->getDebugLoc());
     }
 
     // Replace a use of the cast with a use of the new cast.

llvm/test/DebugInfo/sink-bitcast-di.ll

@@ -0,0 +1,37 @@
+; RUN: opt -S -debugify -codegenprepare < %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"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare void @foo(i32)
+
+declare void @slowpath(i32, i32*)
+
+; Is DI maintained after sinking bitcast?
+define void @test(i1 %cond, i64* %base) {
+; CHECK-LABEL: @test
+entry:
+  %addr = getelementptr inbounds i64, i64* %base, i64 5
+  %casted = bitcast i64* %addr to i32*
+  br i1 %cond, label %if.then, label %fallthrough
+
+if.then:
+; CHECK-LABEL: if.then:
+; CHECK: bitcast i64* %addr to i32*, !dbg ![[castLoc:[0-9]+]]
+  %v1 = load i32, i32* %casted, align 4
+  call void @foo(i32 %v1)
+  %cmp = icmp eq i32 %v1, 0
+  br i1 %cmp, label %rare.1, label %fallthrough
+
+fallthrough:
+  ret void
+
+rare.1:
+; CHECK-LABEL: rare.1:
+; CHECK: bitcast i64* %addr to i32*, !dbg ![[castLoc]]
+  call void @slowpath(i32 %v1, i32* %casted) ;; NOT COLD
+  br label %fallthrough
+}
+
+; CHECK: ![[castLoc]] = !DILocation(line: 2