[gem5-dev] changeset in gem5: gpu-compute: fix segfault when constructing G...

[Tony Gutierrez]

changeset 511b47e9b9bc in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=511b47e9b9bc
description:
        gpu-compute: fix segfault when constructing GPUExecContext

        the GPUExecContext context currently stores a reference to its parent 
WF's
        GPUISA object, however there are some special instructions that do not 
have
        an associated WF. when these objects are constructed they set their WF 
pointer
        to null, which causes the GPUExecContext to segfault when trying to
        dereference
        the WF pointer to get at the WF's GPUISA object. here we change the 
GPUISA
        reference in the GPUExecContext class to a pointer so that it may be 
set to
        null.

diffstat:

 src/gpu-compute/gpu_exec_context.cc |  8 +++++---
 src/gpu-compute/gpu_exec_context.hh |  2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diffs (40 lines):

diff -r 499071baed7b -r 511b47e9b9bc src/gpu-compute/gpu_exec_context.cc
--- a/src/gpu-compute/gpu_exec_context.cc       Mon Nov 21 15:38:30 2016 -0500
+++ b/src/gpu-compute/gpu_exec_context.cc       Mon Nov 21 15:40:03 2016 -0500
@@ -37,7 +37,7 @@
 #include "gpu-compute/wavefront.hh"
 
 GPUExecContext::GPUExecContext(ComputeUnit *_cu, Wavefront *_wf)
-    : cu(_cu), wf(_wf), gpuISA(_wf->gpuISA())
+    : cu(_cu), wf(_wf), gpuISA(_wf ? &_wf->gpuISA() : nullptr)
 {
 }
 
@@ -56,11 +56,13 @@
 TheGpuISA::MiscReg
 GPUExecContext::readMiscReg(int opIdx) const
 {
-    return gpuISA.readMiscReg(opIdx);
+    assert(gpuISA);
+    return gpuISA->readMiscReg(opIdx);
 }
 
 void
 GPUExecContext::writeMiscReg(int opIdx, TheGpuISA::MiscReg operandVal)
 {
-    gpuISA.writeMiscReg(opIdx, operandVal);
+    assert(gpuISA);
+    gpuISA->writeMiscReg(opIdx, operandVal);
 }
diff -r 499071baed7b -r 511b47e9b9bc src/gpu-compute/gpu_exec_context.hh
--- a/src/gpu-compute/gpu_exec_context.hh       Mon Nov 21 15:38:30 2016 -0500
+++ b/src/gpu-compute/gpu_exec_context.hh       Mon Nov 21 15:40:03 2016 -0500
@@ -55,7 +55,7 @@
   protected:
     ComputeUnit *cu;
     Wavefront *wf;
-    TheGpuISA::GPUISA &gpuISA;
+    TheGpuISA::GPUISA *gpuISA;
 };
 
 #endif // __GPU_EXEC_CONTEXT_HH__
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