feature, either build the JIT in debug mode to enable it by default or pass
-jit-emit-debug to lli.
Right now, the only debug information that this communicates to GDB is call
frame information, since it's already being generated to support exceptions in
the JIT. Eventually, when DWARF generation isn't tied so tightly to AsmPrinter,
it will be easy to push that information to GDB through this interface.
Here's a step-by-step breakdown of how the feature works:
- The JIT generates the machine code and DWARF call frame info
(.eh_frame/.debug_frame) for a function into memory.
- The JIT copies that info into an in-memory ELF file with a symbol for the
function.
- The JIT creates a code entry pointing to the ELF buffer and adds it to a
linked list hanging off of a global descriptor at a special symbol that GDB
knows about.
- The JIT calls a function marked noinline that GDB knows about and has put an
internal breakpoint in.
- GDB catches the breakpoint and reads the global descriptor to look for new
code.
- When sees there is new code, it reads the ELF from the inferior's memory and
adds it to itself as an object file.
- The JIT continues, and the next time we stop the program, we are able to
produce a proper backtrace.
Consider running the following program through the JIT:
#include <stdio.h>
void baz(short z) {
long w = z + 1;
printf("%d, %x\n", w, *((int*)NULL)); // SEGFAULT here
}
void bar(short y) {
int z = y + 1;
baz(z);
}
void foo(char x) {
short y = x + 1;
bar(y);
}
int main(int argc, char** argv) {
char x = 1;
foo(x);
}
Here is a backtrace before this patch:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x2aaaabdfbd10 (LWP 25476)]
0x00002aaaabe7d1a8 in ?? ()
(gdb) bt
#0 0x00002aaaabe7d1a8 in ?? ()
#1 0x0000000000000003 in ?? ()
#2 0x0000000000000004 in ?? ()
#3 0x00032aaaabe7cfd0 in ?? ()
#4 0x00002aaaabe7d12c in ?? ()
#5 0x00022aaa00000003 in ?? ()
#6 0x00002aaaabe7d0aa in ?? ()
#7 0x01000002abe7cff0 in ?? ()
#8 0x00002aaaabe7d02c in ?? ()
#9 0x0100000000000001 in ?? ()
#10 0x00000000014388e0 in ?? ()
#11 0x00007fff00000001 in ?? ()
#12 0x0000000000b870a2 in llvm::JIT::runFunction (this=0x1405b70,
F=0x14024e0, ArgValues=@0x7fffffffe050)
at /home/rnk/llvm-gdb/lib/ExecutionEngine/JIT/JIT.cpp:395
#13 0x0000000000baa4c5 in llvm::ExecutionEngine::runFunctionAsMain
(this=0x1405b70, Fn=0x14024e0, argv=@0x13f06f8, envp=0x7fffffffe3b0)
at /home/rnk/llvm-gdb/lib/ExecutionEngine/ExecutionEngine.cpp:377
#14 0x00000000007ebd52 in main (argc=2, argv=0x7fffffffe398,
envp=0x7fffffffe3b0) at /home/rnk/llvm-gdb/tools/lli/lli.cpp:208
And a backtrace after this patch:
Program received signal SIGSEGV, Segmentation fault.
0x00002aaaabe7d1a8 in baz ()
(gdb) bt
#0 0x00002aaaabe7d1a8 in baz ()
#1 0x00002aaaabe7d12c in bar ()
#2 0x00002aaaabe7d0aa in foo ()
#3 0x00002aaaabe7d02c in main ()
#4 0x0000000000b870a2 in llvm::JIT::runFunction (this=0x1405b70,
F=0x14024e0, ArgValues=...)
at /home/rnk/llvm-gdb/lib/ExecutionEngine/JIT/JIT.cpp:395
#5 0x0000000000baa4c5 in llvm::ExecutionEngine::runFunctionAsMain
(this=0x1405b70, Fn=0x14024e0, argv=..., envp=0x7fffffffe3c0)
at /home/rnk/llvm-gdb/lib/ExecutionEngine/ExecutionEngine.cpp:377
#6 0x00000000007ebd52 in main (argc=2, argv=0x7fffffffe3a8,
envp=0x7fffffffe3c0) at /home/rnk/llvm-gdb/tools/lli/lli.cpp:208
llvm-svn: 82418
so that nonlocal and partially redundant loads can use it as well.
The testcase shows examples of craziness this can handle. This triggers
*many* times in 176.gcc.
llvm-svn: 82403
(and load -> load) when the base pointers must alias but when
they are different types. This occurs very very frequently in
176.gcc and other code that uses bitfields a lot.
llvm-svn: 82399
U lib/CodeGen/AsmPrinter/DwarfException.cpp
U lib/CodeGen/AsmPrinter/DwarfException.h
--- Reverse-merging r82274 into '.':
U lib/Target/TargetLoweringObjectFile.cpp
G lib/CodeGen/AsmPrinter/DwarfException.cpp
These revisions were breaking everything.
llvm-svn: 82396
1. Change some "\n" -> '\n'.
2. eliminte some std::string's by using raw_ostream::indent.
3. move a bunch of code out of the main arg parser routine into
a new static HandlePrefixedOrGroupedOption function.
4. Greatly simplify the implementation of getOptionPred, and make
it avoid splitting prefix options at = when that doesn't match
a non-prefix option.
llvm-svn: 82362
internal, they shouldn't use the indirect pointer stuff. In the case of
throw_rethrow_test, it was marked as 'internal' and calculated its own offset to
its contents.
llvm-svn: 82354
stringref because they may not be nul terminated. For options like -Lfoo
this now avoids a O(n) temporary std::strings where N is the length of
the string after -L.
llvm-svn: 82345
we pushed the beginning of the interval back 1, so the
interval would overlap with inputs that die. We were
also pushing the end of the interval back 1, though,
which means the earlyclobber didn't overlap with other
output operands. Don't do this. PR 4964.
llvm-svn: 82342
to. This can be combined with LCSSA or SSI form to store more information on a
PHINode than can be computed by looking at its incoming values.
llvm-svn: 82317
into the __DATA section. At launch time, dyld has to update most of the section
to fix up the type info pointers. It's better to place it into the __TEXT
section and use pc-rel indirect pointer encodings. Similar to the personality
routine.
llvm-svn: 82274
getSymbolForDwarfGlobalReference is smart enough to know that it
needs to register the stub it references with MachineModuleInfoMachO,
so that it gets emitted at the end of the file.
Move stub emission from X86ATTAsmPrinter::doFinalization to the
new X86ATTAsmPrinter::EmitEndOfAsmFile asmprinter hook. The important
thing here is that EmitEndOfAsmFile is called *after* the ehframes are
emitted, so we get all the stubs.
This allows us to remove a gross hack from the asmprinter where it would
"just know" that it needed to output stubs for personality functions.
Now this is all driven from a consistent interface.
The testcase change is just reordering the expected output now that the
stubs come out after the ehframe instead of before.
This also unblocks other changes that Bill wants to make.
llvm-svn: 82269
In getMallocArraySize(), fix bug in the case that array size is the product of 2 constants.
Extend isArrayMalloc() and getMallocArraySize() to handle case where malloc is used as char array.
Ensure that ArraySize in LowerAllocations::runOnBasicBlock() is correct type.
Extend Instruction::isSafeToSpeculativelyExecute() to handle malloc calls.
Add verification for malloc calls.
Reviewed by Dan Gohman.
llvm-svn: 82257
This can be seen on CodeGen/Generic/2006-09-06-SwitchLowering.ll. But it's not known to cause any real regression (but I have added an assertion for it now).
llvm-svn: 82214
where the induction variable has a non-unit stride, such as {0,+,2}, and
there are expressions such as {1,+,2} inside the loop formed with
or or add nsw operators.
llvm-svn: 82151
Reid Kleckner