spirv-opt: Invalidate analyses in DeadBranchElimPass (KhronosGroup#6764)

Invalidate kAnalysisCFG, kAnalysisDominatorAnalysis, and
kAnalysisStructuredCFG
analyses when DeadBranchElimPass makes changes to basic blocks. This
forces
FixBlockOrder() to rebuild them rather than using stale caches
containing
deleted basic block references.

Fixes KhronosGroup#6632

Author: s-perron

source/opt/dead_branch_elim_pass.cpp

@@ -480,7 +480,12 @@ Pass::Status DeadBranchElimPass::Process() {
     return EliminateDeadBranches(fp);
   };
   bool modified = context()->ProcessReachableCallTree(pfn);
-  if (modified) FixBlockOrder();
+  if (modified) {
+    context()->InvalidateAnalyses(IRContext::kAnalysisCFG |
+                                  IRContext::kAnalysisDominatorAnalysis |
+                                  IRContext::kAnalysisStructuredCFG);
+    FixBlockOrder();
+  }
   return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange;
 }
 

test/opt/dead_branch_elim_test.cpp

@@ -16,7 +16,6 @@
 #include <string>
 
 #include "test/opt/pass_fixture.h"
-#include "test/opt/pass_utils.h"
 
 namespace spvtools {
 namespace opt {
@@ -3349,6 +3348,95 @@ OpFunctionEnd
   SinglePassRunAndCheck<DeadBranchElimPass>(text, text, false);
 }
 
+TEST_F(DeadBranchElimTest, CFGAndDominatorsStaleCrash) {
+  const std::string text = R"(
+               OpCapability Addresses
+               OpCapability Kernel
+               OpCapability Int64
+               OpMemoryModel Physical64 OpenCL
+               OpEntryPoint Kernel %1 "main_kernel"
+       %void = OpTypeVoid
+       %uint = OpTypeInt 32 0
+      %ulong = OpTypeInt 64 0
+%_ptr_CrossWorkgroup_uint = OpTypePointer CrossWorkgroup %uint
+          %6 = OpTypeFunction %void %_ptr_CrossWorkgroup_uint %ulong
+       %bool = OpTypeBool
+       %true = OpConstantTrue %bool
+          %1 = OpFunction %void None %6
+          %9 = OpFunctionParameter %_ptr_CrossWorkgroup_uint
+         %10 = OpFunctionParameter %ulong
+         %11 = OpLabel
+               OpSelectionMerge %12 None
+               OpBranchConditional %true %12 %13
+         %12 = OpLabel
+               OpBranch %14
+         %13 = OpLabel
+               OpReturn
+         %15 = OpLabel
+               OpLoopMerge %16 %17 None
+               OpBranch %18
+         %18 = OpLabel
+               OpSelectionMerge %19 None
+               OpBranchConditional %true %20 %20
+         %20 = OpLabel
+               OpBranch %19
+         %19 = OpLabel
+               OpBranch %17
+         %17 = OpLabel
+               OpBranch %15
+         %16 = OpLabel
+               OpBranch %14
+         %14 = OpLabel
+               OpReturn
+               OpFunctionEnd
+)";
+
+  std::unique_ptr<IRContext> context = BuildModule(
+      SPV_ENV_UNIVERSAL_1_1, nullptr, text, SPV_TEXT_TO_BINARY_OPTION_NONE);
+  ASSERT_NE(nullptr, context);
+
+  // Force dominator analysis to be cached for the function.
+  Function* func = &*context->module()->begin();
+  context->GetDominatorAnalysis(func);
+
+  DeadBranchElimPass pass;
+  auto status = pass.Run(context.get());
+
+  EXPECT_EQ(Pass::Status::SuccessWithChange, status);
+
+  std::vector<uint32_t> optimized_bin;
+  context->module()->ToBinary(&optimized_bin, /* skip_nop = */ true);
+  std::string optimized_asm;
+  SpirvTools tools(SPV_ENV_UNIVERSAL_1_1);
+  EXPECT_TRUE(tools.Disassemble(optimized_bin, &optimized_asm));
+
+  const std::string expected = R"(OpCapability Addresses
+OpCapability Kernel
+OpCapability Int64
+OpMemoryModel Physical64 OpenCL
+OpEntryPoint Kernel %1 "main_kernel"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%ulong = OpTypeInt 64 0
+%_ptr_CrossWorkgroup_uint = OpTypePointer CrossWorkgroup %uint
+%6 = OpTypeFunction %void %_ptr_CrossWorkgroup_uint %ulong
+%bool = OpTypeBool
+%true = OpConstantTrue %bool
+%1 = OpFunction %void None %6
+%9 = OpFunctionParameter %_ptr_CrossWorkgroup_uint
+%10 = OpFunctionParameter %ulong
+%11 = OpLabel
+OpBranch %12
+%12 = OpLabel
+OpBranch %14
+%14 = OpLabel
+OpReturn
+OpFunctionEnd
+)";
+
+  EXPECT_EQ(expected, optimized_asm);
+}
+
 // TODO(greg-lunarg): Add tests to verify handling of these cases:
 //
 //    More complex control flow