From ed29dbaafa49bb8c9039a35f768244c394411fea Mon Sep 17 00:00:00 2001
From: Jeremy Morse <jeremy.morse.llvm@gmail.com>
Date: Tue, 15 Oct 2019 10:46:24 +0000
Subject: [DebugInfo] Remove some users of DBG_VALUEs IsIndirect field

This patch kills off a significant user of the "IsIndirect" field of
DBG_VALUE machine insts. Brought up in in PR41675, IsIndirect is
techncally redundant as it can be expressed by the DIExpression of a
DBG_VALUE inst, and it isn't helpful to have two ways of expressing
things.

Rather than setting IsIndirect, have DBG_VALUE creators add an extra deref
to the insts DIExpression. There should now be no appearences of
IsIndirect=True from isel down to LiveDebugVariables / VirtRegRewriter,
which is ensured by an assertion in LDVImpl::handleDebugValue. This means
we also get to delete the IsIndirect handling in LiveDebugVariables. Tests
can be upgraded by for example swapping the following IsIndirect=True
DBG_VALUE:

  DBG_VALUE $somereg, 0, !123, !DIExpression(DW_OP_foo)

With one where the indirection is in the DIExpression, by _appending_
a deref:

  DBG_VALUE $somereg, $noreg, !123, !DIExpression(DW_OP_foo, DW_OP_deref)

Which both mean the same thing.

Most of the test changes in this patch are updates of that form; also some
changes in how the textual assembly printer handles these insts.

Differential Revision: https://reviews.llvm.org/D68945

llvm-svn: 374877
---
 llvm/lib/CodeGen/SelectionDAG/FastISel.cpp | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

(limited to 'llvm/lib/CodeGen/SelectionDAG/FastISel.cpp')

diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 347776b2367..23f57f216d2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -1389,9 +1389,11 @@ bool FastISel::selectIntrinsicCall(const IntrinsicInst *II) {
              "Expected inlined-at fields to agree");
       // A dbg.declare describes the address of a source variable, so lower it
       // into an indirect DBG_VALUE.
+      auto *Expr = DI->getExpression();
+      Expr = DIExpression::append(Expr, {dwarf::DW_OP_deref});
       BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
-              TII.get(TargetOpcode::DBG_VALUE), /*IsIndirect*/ true,
-              *Op, DI->getVariable(), DI->getExpression());
+              TII.get(TargetOpcode::DBG_VALUE), /*IsIndirect*/ false,
+              *Op, DI->getVariable(), Expr);
     } else {
       // We can't yet handle anything else here because it would require
       // generating code, thus altering codegen because of debug info.
@@ -1415,19 +1417,19 @@ bool FastISel::selectIntrinsicCall(const IntrinsicInst *II) {
       if (CI->getBitWidth() > 64)
         BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II)
             .addCImm(CI)
-            .addImm(0U)
+            .addReg(0U)
             .addMetadata(DI->getVariable())
             .addMetadata(DI->getExpression());
       else
         BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II)
             .addImm(CI->getZExtValue())
-            .addImm(0U)
+            .addReg(0U)
             .addMetadata(DI->getVariable())
             .addMetadata(DI->getExpression());
     } else if (const auto *CF = dyn_cast<ConstantFP>(V)) {
       BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II)
           .addFPImm(CF)
-          .addImm(0U)
+          .addReg(0U)
           .addMetadata(DI->getVariable())
           .addMetadata(DI->getExpression());
     } else if (unsigned Reg = lookUpRegForValue(V)) {
-- 
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