[DebugInfo] LowerDbgDeclare: Add derefs when handling CallInst users

LowerDbgDeclare inserts a dbg.value before each use of an address
described by a dbg.declare. When inserting a dbg.value before a CallInst
use, however, it fails to append DW_OP_deref to the DIExpression.

The DW_OP_deref is needed to reflect the fact that a dbg.value describes
a source variable directly (as opposed to a dbg.declare, which relies on
pointer indirection).

This patch adds in the DW_OP_deref where needed. This results in the
correct values being shown during a debug session for a program compiled
with ASan and optimizations (see https://reviews.llvm.org/D49520). Note
that ConvertDebugDeclareToDebugValue is already correct -- no changes
there were needed.

One complication is that SelectionDAG is unable to distinguish between
direct and indirect frame-index (FRAMEIX) SDDbgValues. This patch also
fixes this long-standing issue in order to not regress integration tests
relying on the incorrect assumption that all frame-index SDDbgValues are
indirect. This is a necessary fix: the newly-added DW_OP_derefs cannot
be lowered properly otherwise. Basically the fix prevents a direct
SDDbgValue with DIExpression(DW_OP_deref) from being dereferenced twice
by a debugger. There were a handful of tests relying on this incorrect
"FRAMEIX => indirect" assumption which actually had incorrect
DW_AT_locations: these are all fixed up in this patch.

Testing:

- check-llvm, and an end-to-end test using lldb to debug an optimized
  program.
- Existing unit tests for DIExpression::appendToStack fully cover the
  new DIExpression::append utility.
- check-debuginfo (the debug info integration tests)

Differential Revision: https://reviews.llvm.org/D49454

llvm-svn: 338069

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/test/DebugInfo/Mips/dsr-fixed-objects.ll b/llvm/test/DebugInfo/Mips/dsr-fixed-objects.ll
index 010186852ee..ebbe64a0c42 100644
--- a/llvm/test/DebugInfo/Mips/dsr-fixed-objects.ll
+++ b/llvm/test/DebugInfo/Mips/dsr-fixed-objects.ll
@@ -20,11 +20,12 @@ declare void @llvm.lifetime.end(i64, i8* nocapture)
 
 declare void @foo(i32*)
 
+; CHECK: DW_AT_name {{.*}}"f0"
 ; CHECK: DW_AT_name {{.*}}"e"
 ; CHECK: DW_TAG_variable
 ; CHECK-NEXT: DW_AT_location [DW_FORM_sec_offset] (
 ; CHECK-NEXT:   [0x00000028, 0x0000002c): DW_OP_reg1 AT_64
-; CHECK-NEXT:   [0x0000002c, 0x00000048): DW_OP_breg29 SP_64+16, DW_OP_deref)
+; CHECK-NEXT:   [0x0000002c, 0x00000048): DW_OP_breg29 SP_64+16)
 ; CHECK-NEXT: DW_AT_name [DW_FORM_strp]     ( .debug_str[0x0000006b] = "x")
 
 define i32 @f0(i32 signext %a, i32 signext %b, i32 signext %c, i32 signext %d, i32 signext %e) !dbg !4 {
@@ -55,7 +56,7 @@ entry:
 ; CHECK: DW_TAG_variable
 ; CHECK-NEXT: DW_AT_location [DW_FORM_sec_offset]  (
 ; CHECK-NEXT:   [0x00000080, 0x00000084): DW_OP_reg1 AT_64
-; CHECK-NEXT:   [0x00000084, 0x00000098): DW_OP_breg29 SP_64+16, DW_OP_deref)
+; CHECK-NEXT:   [0x00000084, 0x00000098): DW_OP_breg29 SP_64+16)
 ; CHECK-NEXT: DW_AT_name [DW_FORM_strp]     ( .debug_str[0x0000006b] = "x")
 
 define i32 @f1(i32 signext %a, i32 signext %b, i32 signext %c, i32 signext %d, i32 signext %e) !dbg !15 {