[DebugInfo] Maintain DI when converting GEP to bitcast

[ergawy]

Summary

When a GEP with all zero indices is converted to bitcast, its DI wasn't
copied over to the newly created instruction. This patch fixes that bug.

[vsk]

LGTM. Thanks!

llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp

if (BinOp && (BinOp->getOpcode() == Instruction::AShr ||
     return false;
   }
 
   if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
     if (GEPI->hasAllZeroIndices()) {
       /// The GEP operand must be a pointer, so must its result -> BitCast
       Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
                                         GEPI->getName(), GEPI);
+      NC->setDebugLoc(GEPI->getDebugLoc());
       GEPI->replaceAllUsesWith(NC);
       GEPI->eraseFromParent();
       ++NumGEPsElim;
       optimizeInst(NC, ModifiedDT);
       return true;
     }
     if (tryUnmergingGEPsAcrossIndirectBr(GEPI, TTI)) {
       return true;

llvm/trunk/test/DebugInfo/X86/bitcast-di.ll

+; RUN: opt -mtriple=x86_64-unknown-linux-gnu -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"
+
+@x = external global [1 x [2 x <4 x float>]]
+
+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
+}
+
+; Is DI maitained when a GEP with all zero indices gets converted to bitcast?
+define void @test2() {
+; CHECK-LABEL: @test2
+load.i145:
+; CHECK: bitcast [1 x [2 x <4 x float>]]* @x to [2 x <4 x float>]*, !dbg ![[castLoc2:[0-9]+]]
+  %x_offset = getelementptr [1 x [2 x <4 x float>]], [1 x [2 x <4 x float>]]* @x, i32 0, i64 0
+  ret void
+}
+
+; CHECK: ![[castLoc]] = !DILocation(line: 2
+; CHECK: ![[castLoc2]] = !DILocation(line: 11
 No newline at end of file

llvm/trunk/test/DebugInfo/X86/sink-bitcast-di.ll

-; RUN: opt -mtriple=x86_64-unknown-linux-gnu -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