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[spirv-reader] Check some merge block dominance 

A merge block must be dominated by its own header.
This CL checks the cases where that fails because the
merge block is also the:
- the default or case header for a switch (a different header)
- the true-head, false-head, or premerge-head for an if-selection
  with a different header

Bug: tint:3
Change-Id: I6dd1fae162e9d33bd9a0b43d3ca9558cebed058b
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/22680
Reviewed-by: dan sinclair <dsinclair@google.com>
This commit is contained in:
David Neto 2020-06-08 15:14:22 +00:00
parent dc8efd4095
commit bdcd04b1a2
2 changed files with 275 additions and 8 deletions
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62
src/reader/spirv/function.cc
View File

@ -943,6 +943,17 @@ bool FunctionEmitter::FindSwitchCaseHeaders() {
<< default_block->default_head_for->begin_id << " and "
<< construct->begin_id;
}
if ((default_block->header_for_merge != 0) &&
(default_block->header_for_merge != construct->begin_id)) {
// The switch instruction for this default block is an alternate path to
// the merge block, and hence the merge block is not dominated by its own
// (different) header.
return Fail() << "Block " << default_block->id
<< " is the default block for switch-selection header "
<< construct->begin_id << " and also the merge block for "
<< default_block->header_for_merge
<< " (violates dominance rule)";
}
default_block->default_head_for = construct.get();
default_block->default_is_merge = default_block->pos == construct->end_pos;
@ -991,6 +1002,17 @@ bool FunctionEmitter::FindSwitchCaseHeaders() {
<< " to case target block " << case_target_id
<< " escapes the selection construct";
}
if (case_block->header_for_merge != 0 &&
case_block->header_for_merge != construct->begin_id) {
// The switch instruction for this case block is an alternate path to
// the merge block, and hence the merge block is not dominated by its
// own (different) header.
return Fail() << "Block " << case_block->id
<< " is a case block for switch-selection header "
<< construct->begin_id << " and also the merge block for "
<< case_block->header_for_merge
<< " (violates dominance rule)";
}
// Mark the target as a case target.
if (case_block->case_head_for) {
@ -1309,6 +1331,29 @@ bool FunctionEmitter::FindIfSelectionInternalHeaders() {
false_head_info->exclusive_false_head_for = construct.get();
}
if ((true_head_info->header_for_merge != 0) &&
(true_head_info->header_for_merge != construct->begin_id)) {
// The OpBranchConditional instruction for the true head block is an
// alternate path to the merge block, and hence the merge block is not
// dominated by its own (different) header.
return Fail() << "Block " << true_head
<< " is the true branch for if-selection header "
<< construct->begin_id << " and also the merge block for header block "
<< true_head_info->header_for_merge
<< " (violates dominance rule)";
}
if ((false_head_info->header_for_merge != 0) &&
(false_head_info->header_for_merge != construct->begin_id)) {
// The OpBranchConditional instruction for the false head block is an
// alternate path to the merge block, and hence the merge block is not
// dominated by its own (different) header.
return Fail() << "Block " << false_head
<< " is the false branch for if-selection header "
<< construct->begin_id << " and also the merge block for header block "
<< false_head_info->header_for_merge
<< " (violates dominance rule)";
}
if (contains_true && contains_false && (true_head_pos != false_head_pos)) {
// This construct has both a "then" clause and an "else" clause.
//
@ -1382,6 +1427,23 @@ bool FunctionEmitter::FindIfSelectionInternalHeaders() {
auto* dest_block_info = GetBlockInfo(dest_id);
dest_block_info->premerge_head_for = construct.get();
if_header_info->premerge_head = dest_block_info;
if (dest_block_info->header_for_merge != 0) {
// Premerge has two edges coming into it, from the then-clause
// and the else-clause. It's also, by construction, not the
// merge block of the if-selection. So it must not be a merge
// block itself. The OpBranchConditional instruction for the
// false head block is an alternate path to the merge block, and
// hence the merge block is not dominated by its own (different)
// header.
return Fail()
<< "Block " << premerge_id
<< " is the merge block for " << dest_block_info->header_for_merge
<< " but has alternate paths reaching it, starting from"
<< " blocks " << true_head << " and " << false_head
<< " which are the true and false branches for the"
<< " if-selection header block " << construct->begin_id
<< " (violates dominance rule)";
}
}
break;
}

221
src/reader/spirv/function_cfg_test.cc
View File

@ -79,15 +79,22 @@ std::string CommonTypes() {
)";
}
/// Runs the necessary flow until and including finding switch case
/// headers.
/// @returns the result of finding switch case headers.
bool FlowFindSwitchCaseHeaders(FunctionEmitter* fe) {
fe->RegisterBasicBlocks();
EXPECT_TRUE(fe->RegisterMerges()) << fe->parser()->error();
fe->ComputeBlockOrderAndPositions();
EXPECT_TRUE(fe->VerifyHeaderContinueMergeOrder()) << fe->parser()->error();
EXPECT_TRUE(fe->LabelControlFlowConstructs()) << fe->parser()->error();
return fe->FindSwitchCaseHeaders();
}
/// Runs the necessary flow until and including classify CFG edges,
/// @returns the result of classify CFG edges.
bool FlowClassifyCFGEdges(FunctionEmitter* fe) {
fe->RegisterBasicBlocks();
fe->ComputeBlockOrderAndPositions();
EXPECT_TRUE(fe->VerifyHeaderContinueMergeOrder()) << fe->parser()->error();
EXPECT_TRUE(fe->RegisterMerges()) << fe->parser()->error();
EXPECT_TRUE(fe->LabelControlFlowConstructs()) << fe->parser()->error();
EXPECT_TRUE(fe->FindSwitchCaseHeaders()) << fe->parser()->error();
EXPECT_TRUE(FlowFindSwitchCaseHeaders(fe)) << fe->parser()->error();
return fe->ClassifyCFGEdges();
}
@ -3676,7 +3683,7 @@ TEST_F(SpvParserTest, FindSwitchCaseHeaders_DefaultCantEscapeSwitch) {
"escapes the selection construct"));
}
TEST_F(SpvParserTest, FindSwitchCaseHeaders_DefaultForTwoSwitches) {
TEST_F(SpvParserTest, FindSwitchCaseHeaders_DefaultForTwoSwitches_AsMerge) {
auto assembly = CommonTypes() + R"(
%100 = OpFunction %void None %voidfn
@ -3711,7 +3718,51 @@ TEST_F(SpvParserTest, FindSwitchCaseHeaders_DefaultForTwoSwitches) {
fe.RegisterMerges();
fe.LabelControlFlowConstructs();
EXPECT_FALSE(fe.FindSwitchCaseHeaders());
EXPECT_THAT(p->error(), Eq("Block 89 is declared as the default target for "
EXPECT_THAT(p->error(),
Eq("Block 89 is the default block for switch-selection header 10 "
"and also the merge block for 50 (violates dominance rule)"));
}
TEST_F(SpvParserTest,
FindSwitchCaseHeaders_DefaultForTwoSwitches_AsCaseClause) {
auto assembly = CommonTypes() + R"(
%100 = OpFunction %void None %voidfn
%10 = OpLabel
OpSelectionMerge %99 None
OpSwitch %selector %80 20 %20
%20 = OpLabel
OpBranch %50
%50 = OpLabel
OpSelectionMerge %89 None
OpSwitch %selector %80 60 %60
%60 = OpLabel
OpBranch %89 ; fallthrough
%80 = OpLabel ; default for both switches
OpBranch %89
%89 = OpLabel ; inner selection merge
OpBranch %99
%99 = OpLabel ; outer selection mege
OpReturn
OpFunctionEnd
)";
auto* p = parser(test::Assemble(assembly));
ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions()) << p->error();
FunctionEmitter fe(p, *spirv_function(100));
fe.RegisterBasicBlocks();
fe.ComputeBlockOrderAndPositions();
EXPECT_TRUE(fe.VerifyHeaderContinueMergeOrder());
fe.RegisterMerges();
fe.LabelControlFlowConstructs();
EXPECT_FALSE(fe.FindSwitchCaseHeaders());
EXPECT_THAT(p->error(), Eq("Block 80 is declared as the default target for "
"two OpSwitch instructions, at blocks 10 and 50"));
}
@ -5994,6 +6045,70 @@ TEST_F(SpvParserTest,
"construct starting at block 50; branch bypasses merge block 80"));
}
TEST_F(
SpvParserTest,
FindSwitchCaseHeaders_DomViolation_SwitchCase_CantBeMergeForOtherConstruct) {
auto assembly = CommonTypes() + R"(
%100 = OpFunction %void None %voidfn
%10 = OpLabel
OpSelectionMerge %99 None
OpSwitch %selector %99 20 %20 50 %50
%20 = OpLabel
OpSelectionMerge %50 None
OpBranchConditional %cond %30 %50
%30 = OpLabel
OpBranch %50
%50 = OpLabel ; case and merge block. Error
OpBranch %99
%99 = OpLabel
OpReturn
)";
auto* p = parser(test::Assemble(assembly));
ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions()) << p->error();
FunctionEmitter fe(p, *spirv_function(100));
EXPECT_FALSE(FlowFindSwitchCaseHeaders(&fe));
EXPECT_THAT(p->error(),
Eq("Block 50 is a case block for switch-selection header 10 and "
"also the merge block for 20 (violates dominance rule)"));
}
TEST_F(
SpvParserTest,
ClassifyCFGEdges_DomViolation_SwitchDefault_CantBeMergeForOtherConstruct) {
auto assembly = CommonTypes() + R"(
%100 = OpFunction %void None %voidfn
%10 = OpLabel
OpSelectionMerge %99 None
OpSwitch %selector %50 20 %20
%20 = OpLabel
OpSelectionMerge %50 None
OpBranchConditional %cond %30 %50
%30 = OpLabel
OpBranch %50
%50 = OpLabel ; default-case and merge block. Error
OpBranch %99
%99 = OpLabel
OpReturn
)";
auto* p = parser(test::Assemble(assembly));
ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions()) << p->error();
FunctionEmitter fe(p, *spirv_function(100));
EXPECT_FALSE(FlowFindSwitchCaseHeaders(&fe));
EXPECT_THAT(p->error(),
Eq("Block 50 is the default block for switch-selection header 10 "
"and also the merge block for 20 (violates dominance rule)"));
}
TEST_F(SpvParserTest, ClassifyCFGEdges_TooManyBackedges) {
auto assembly = CommonTypes() + R"(
%100 = OpFunction %void None %voidfn
@ -6653,6 +6768,96 @@ TEST_F(SpvParserTest, ClassifyCFGEdges_IfBreak_WithForwardToPremerge_IsError) {
"a structured header (it has no merge instruction)"));
}
TEST_F(SpvParserTest, FindIfSelectionInternalHeaders_DomViolation_Merge_CantBeTrueHeader) {
auto assembly = CommonTypes() + R"(
%100 = OpFunction %void None %voidfn
%10 = OpLabel
OpSelectionMerge %99 None
OpBranchConditional %cond %40 %20
%20 = OpLabel
OpSelectionMerge %40 None
OpBranchConditional %cond2 %30 %40
%30 = OpLabel
OpBranch %40
%40 = OpLabel ; inner merge, and true-head for outer if-selection
OpBranch %99
%99 = OpLabel ; outer merge
OpReturn
)";
auto* p = parser(test::Assemble(assembly));
ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions()) << p->error();
FunctionEmitter fe(p, *spirv_function(100));
EXPECT_FALSE(FlowFindIfSelectionInternalHeaders(&fe));
EXPECT_THAT(p->error(), Eq("Block 40 is the true branch for if-selection header 10 and also the merge block for header block 20 (violates dominance rule)"));
}
TEST_F(SpvParserTest, FindIfSelectionInternalHeaders_DomViolation_Merge_CantBeFalseHeader) {
auto assembly = CommonTypes() + R"(
%100 = OpFunction %void None %voidfn
%10 = OpLabel
OpSelectionMerge %99 None
OpBranchConditional %cond %20 %40
%20 = OpLabel
OpSelectionMerge %40 None
OpBranchConditional %cond %30 %40
%30 = OpLabel
OpBranch %40
%40 = OpLabel ; inner merge, and true-head for outer if-selection
OpBranch %99
%99 = OpLabel ; outer merge
OpReturn
)";
auto* p = parser(test::Assemble(assembly));
ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions()) << p->error();
FunctionEmitter fe(p, *spirv_function(100));
EXPECT_FALSE(FlowFindIfSelectionInternalHeaders(&fe));
EXPECT_THAT(p->error(), Eq("Block 40 is the false branch for if-selection header 10 and also the merge block for header block 20 (violates dominance rule)"));
}
TEST_F(SpvParserTest, FindIfSelectionInternalHeaders_DomViolation_Merge_CantBePremerge) {
auto assembly = CommonTypes() + R"(
%100 = OpFunction %void None %voidfn
%10 = OpLabel ; outer if-header
OpSelectionMerge %99 None
OpBranchConditional %cond %20 %50
%20 = OpLabel
OpBranch %70
%50 = OpLabel ; inner if-header
OpSelectionMerge %70 None
OpBranchConditional %cond %60 %70
%60 = OpLabel
OpBranch %70
%70 = OpLabel ; inner merge, and premerge for outer if-selection
OpBranch %80
%80 = OpLabel
OpBranch %99
%99 = OpLabel ; outer merge
OpReturn
)";
auto* p = parser(test::Assemble(assembly));
ASSERT_TRUE(p->BuildAndParseInternalModuleExceptFunctions()) << p->error();
FunctionEmitter fe(p, *spirv_function(100));
EXPECT_FALSE(FlowFindIfSelectionInternalHeaders(&fe));
EXPECT_THAT(p->error(), Eq("Block 70 is the merge block for 50 but has alternate paths reaching it, starting from blocks 20 and 50 which are the true and false branches for the if-selection header block 10 (violates dominance rule)"));
}
TEST_F(SpvParserTest, DISABLED_Codegen_IfBreak_FromThen_ForwardWithinThen) {
// TODO(dneto): We can make this case work, if we injected
// if (!cond2) { rest-of-then-body }