From b572f6421296e7688973014d253e46c54fd64ba3 Mon Sep 17 00:00:00 2001 From: Vedant Kumar Date: Thu, 26 Jul 2018 20:56:53 +0000 Subject: [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 --- llvm/lib/Transforms/Utils/Local.cpp | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'llvm/lib/Transforms/Utils/Local.cpp') diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp index a0e79b68e72..ae3cb077a3a 100644 --- a/llvm/lib/Transforms/Utils/Local.cpp +++ b/llvm/lib/Transforms/Utils/Local.cpp @@ -1419,12 +1419,13 @@ bool llvm::LowerDbgDeclare(Function &F) { } else if (LoadInst *LI = dyn_cast(U)) { ConvertDebugDeclareToDebugValue(DDI, LI, DIB); } else if (CallInst *CI = dyn_cast(U)) { - // This is a call by-value or some other instruction that - // takes a pointer to the variable. Insert a *value* - // intrinsic that describes the alloca. - DIB.insertDbgValueIntrinsic(AI, DDI->getVariable(), - DDI->getExpression(), DDI->getDebugLoc(), - CI); + // This is a call by-value or some other instruction that takes a + // pointer to the variable. Insert a *value* intrinsic that describes + // the variable by dereferencing the alloca. + auto *DerefExpr = + DIExpression::append(DDI->getExpression(), dwarf::DW_OP_deref); + DIB.insertDbgValueIntrinsic(AI, DDI->getVariable(), DerefExpr, + DDI->getDebugLoc(), CI); } } DDI->eraseFromParent(); -- cgit v1.2.3