[lldb-dev] r260768 (Removed many JIT workarounds from IRForTarget) broke expression parser with function on Hexagon

[Ted Woodward via lldb-dev]

I did some digging and found where the ID is being changed from 0x5 to 0xa in the original code.

 

IRForTarget::runOnModule() calls ResolveFunctionPointers(), which gets a Constant * from BuildFunctionPointer(). This Value has an ID of 0xa, and runOnModule() then calls the original Function’s replaceAllUsesWith(), passing in the new Value, changing ID from 0x5 to 0xa.

 

If I comment out the call to ResolveFunctionPointer() in the original code, I get the same error as the current code: “error: Can't run the expression locally: Interpreter doesn't handle one of the expression's operands”

 

So I went to r260768 and added back in the call to ResolveFunctionPointer(), as well as functions that it depended on:

ClangExpressionDeclMap::FindCodeSymbolInContext()

ClangExpressionDeclMap::FindBestAlternateMangledName()

ClangExpressionDeclMap::GetFunctionAddress()

IRForTarget::GetFunctionAddress()

IRForTarget::BuildFunctionPointer()

I commented out the call to RegisterFunctionMetadata() since it didn’t seem to matter.

 

After those changes, I was able to print out main’s info and call functions with the expression parser.

 

Is there anything in these functions that I can get rid of, or is handled by newer code?

 

--

Qualcomm Innovation Center, Inc.

The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

 

From: scallanan at apple.com [mailto:scallanan at apple.com] 
Sent: Tuesday, February 23, 2016 6:38 PM
To: Ted Woodward
Cc: LLDB
Subject: Re: r260768 (Removed many JIT workarounds from IRForTarget) broke expression parser with function on Hexagon

 

At that point, I’d set a watchpoint and see what is setting it. I would expect that

 

  %call = call i32 @factorial(i32 5)

would put a normal value in call, which would then be the value stored by the store instruction

 

  store i32 %call, i32* @"_ZZ12$__lldb_exprPvE19$__lldb_expr_result", align 4

 

The store instruction should not have an operand of function type… right?

 

Sean

 

On Feb 23, 2016, at 4:21 PM, Ted Woodward <ted.woodward at codeaurora.org <mailto:ted.woodward at codeaurora.org> > wrote:

 

Unfortunately, that leads to another error, in the Instruction::Store case. IRInterpreter::ResolveConstantValue() returns an error because it doesn’t like the value id of FunctionVal. “Interpreter couldn't resolve a value during execution”.

 

If I go back 1 commit from r260768 (r260767), it works. The value id is 0xa, ConstantIntVal. So something in r260768 is either setting the value id to 0x5, or keeping the value id from being set to 0xa.

 

Ted

--

Qualcomm Innovation Center, Inc.

The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

 

From: scallanan at apple.com <mailto:scallanan at apple.com>  [mailto:scallanan at apple.com] 
Sent: Tuesday, February 23, 2016 5:41 PM
To: Ted Woodward
Cc: LLDB
Subject: Re: r260768 (Removed many JIT workarounds from IRForTarget) broke expression parser with function on Hexagon

 

Ted,

 

I’m not sure who inside Clang actually sets the value ID – it’s the code generator’s job to make IR, we don’t construct it.

I would be fine with adding FunctionVal to the switch in CanResolveConstant, returning true.

 

Sean

 

On Feb 23, 2016, at 3:28 PM, Ted Woodward < <mailto:ted.woodward at codeaurora.org> ted.woodward at codeaurora.org> wrote:

 

Background: Hexagon clang doesn’t have JIT support, so lldb for Hexagon only uses the IR Interpreter (Codeplay wrote it for us).

 

Sean, r260768 broke the expression parser with functions.

 

Without connecting to a target, I can’t get the info for main:

(lldb) e main

error: Can't run the expression locally: Interpreter doesn't handle one of the expression's operands

 

Connected to a target, I can’t run a function:

(lldb) e factorial(5)

error: Can't run the expression locally: Interpreter doesn't handle one of the expression's operands

 

 

I’ve traced the failure to the call to CanResolveConstant() in IRInterpreter::CanIntepret(). The failure happens on the 2nd operand. In the working case, the Value ID is 0xa – Value::ConstantExprVal. In the failing case, it is 0x5. Since it’s defined in a .def file, I can’t be sure, but my guess is its Value::FunctionVal.

 

 

Where is the Value ID set?

 

 

 

Some info from the expr log:

 

; Function Attrs: nounwind

define void @"_Z12$__lldb_exprPv"(i8* %"$__lldb_arg") #0 {

entry:

  %"$__lldb_arg.addr" = alloca i8*, align 4, !clang.decl.ptr !4

  store i8* %"$__lldb_arg", i8** %"$__lldb_arg.addr", align 4

  %0 = load i8, i8* @"_ZGVZ12$__lldb_exprPvE19$__lldb_expr_result", align 1

  %guard.uninitialized = icmp eq i8 %0, 0

  br i1 %guard.uninitialized, label %init.check, label %init.end

 

init.check:                                       ; preds = %entry

  %call = call i32 @factorial(i32 5)

  store i32 %call, i32* @"_ZZ12$__lldb_exprPvE19$__lldb_expr_result", align 4

  store i8 1, i8* @"_ZGVZ12$__lldb_exprPvE19$__lldb_expr_result", align 1

  br label %init.end

 

init.end:                                         ; preds = %init.check, %entry

  ret void

}

 

 

Unsupported constant: declare i32 @factorial(i32) #1

 

 

Ted

 

--

Qualcomm Innovation Center, Inc.

The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

 

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