From f6cd6ffbc9f8bfa0bbe25dba6a9737607a684bab Mon Sep 17 00:00:00 2001 From: Petr Hosek Date: Mon, 22 Jul 2019 18:52:42 +0000 Subject: [SafeStack] Insert the deref after the offset While debugging code that uses SafeStack, we've noticed that LLVM produces an invalid DWARF. Concretely, in the following example: int main(int argc, char* argv[]) { std::string value = ""; printf("%s\n", value.c_str()); return 0; } DWARF would describe the value variable as being located at: DW_OP_breg14 R14+0, DW_OP_deref, DW_OP_constu 0x20, DW_OP_minus The assembly to get this variable is: leaq -32(%r14), %rbx The order of operations in the DWARF symbols is incorrect in this case. Specifically, the deref is incorrect; this appears to be incorrectly re-inserted in repalceOneDbgValueForAlloca. With this change which inserts the deref after the offset instead of before it, LLVM produces correct DWARF: DW_OP_breg14 R14-32 Differential Revision: https://reviews.llvm.org/D64971 llvm-svn: 366726 --- llvm/test/Transforms/SafeStack/X86/debug-loc2.ll | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'llvm/test/Transforms/SafeStack') diff --git a/llvm/test/Transforms/SafeStack/X86/debug-loc2.ll b/llvm/test/Transforms/SafeStack/X86/debug-loc2.ll index afa143f9c08..30623962691 100644 --- a/llvm/test/Transforms/SafeStack/X86/debug-loc2.ll +++ b/llvm/test/Transforms/SafeStack/X86/debug-loc2.ll @@ -25,7 +25,7 @@ entry: tail call void @llvm.dbg.value(metadata i32* %x1, metadata !10, metadata !24), !dbg !16 ; Supported dbg.value: rewritted based on the [[USP]] value. -; CHECK: call void @llvm.dbg.value(metadata i8* %[[USP]], metadata ![[X1:.*]], metadata !DIExpression(DW_OP_deref, DW_OP_constu, 4, DW_OP_minus)) +; CHECK: call void @llvm.dbg.value(metadata i8* %[[USP]], metadata ![[X1:.*]], metadata !DIExpression(DW_OP_constu, 4, DW_OP_minus, DW_OP_deref)) tail call void @llvm.dbg.value(metadata i32* %x1, metadata !10, metadata !15), !dbg !16 call void @capture(i32* nonnull %x1), !dbg !17 @@ -33,7 +33,7 @@ entry: ; CHECK: call void @llvm.random.metadata.use(metadata ![[EMPTY]]) call void @llvm.random.metadata.use(metadata i32* %x2) -; CHECK: call void @llvm.dbg.value(metadata i8* %[[USP]], metadata ![[X2:.*]], metadata !DIExpression(DW_OP_deref, DW_OP_constu, 8, DW_OP_minus)) +; CHECK: call void @llvm.dbg.value(metadata i8* %[[USP]], metadata ![[X2:.*]], metadata !DIExpression(DW_OP_constu, 8, DW_OP_minus, DW_OP_deref)) call void @llvm.dbg.value(metadata i32* %x2, metadata !12, metadata !15), !dbg !18 call void @capture(i32* nonnull %x2), !dbg !19 ret void, !dbg !20 -- cgit v1.2.3