[llvm] 08d1c43 - llvm-reduce: Add conditional reduction passes
Matt Arsenault via llvm-commits
llvm-commits at lists.llvm.org
Sun Oct 23 15:44:38 PDT 2022
Author: Matt Arsenault
Date: 2022-10-23T15:39:39-07:00
New Revision: 08d1c43c7023a2e955c43fbf4c3f1635f91521e0
URL: https://github.com/llvm/llvm-project/commit/08d1c43c7023a2e955c43fbf4c3f1635f91521e0
DIFF: https://github.com/llvm/llvm-project/commit/08d1c43c7023a2e955c43fbf4c3f1635f91521e0.diff
LOG: llvm-reduce: Add conditional reduction passes
Copy this technique from bugpoint. Before trying to blindly
delete blocks, try to fold branch conditions. This intuitively
makes more sense for a faster reduction, since you can find
dead paths in the function to prune out before trying to bisect
blocks in source order.
Seems to provide some speedup on my multi-hour reduction samples.
This does have the potential to produce testcases with unreachable
blocks. This is already a problem with the existing block
reduction pass. I'm struggling dealing with invalid reductions
in these cases, so in the future this should probably start
deleting those. However, I do sometimes try to reduce failures
in code that becomes unreachable, so I'm not totally sure
what to do here.
Added:
llvm/test/tools/llvm-reduce/reduce-conditionals.ll
Modified:
llvm/tools/llvm-reduce/DeltaManager.cpp
llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.cpp
llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.h
Removed:
################################################################################
diff --git a/llvm/test/tools/llvm-reduce/reduce-conditionals.ll b/llvm/test/tools/llvm-reduce/reduce-conditionals.ll
new file mode 100644
index 000000000000..a832673d7350
--- /dev/null
+++ b/llvm/test/tools/llvm-reduce/reduce-conditionals.ll
@@ -0,0 +1,39 @@
+; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=simplify-conditionals-true --test FileCheck --test-arg --check-prefixes=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck --check-prefixes=RESULT-TRUE %s < %t
+
+; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=simplify-conditionals-false --test FileCheck --test-arg --check-prefixes=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck --check-prefixes=RESULT-FALSE %s < %t
+
+; CHECK-INTERESTINGNESS-LABEL: @func(
+; CHECK-INTERESTINGNESS: store i32 1,
+
+; RESULT-TRUE: bb0:
+; RESULT-TRUE: store i32 0, ptr null, align 4
+; RESULT-TRUE-NEXT: store i32 1, ptr null, align 4
+; RESULT-TRUE-NEXT: br label %bb2
+; RESULT-TRUE-NOT: bb1
+
+
+; RESULT-FALSE: bb0:
+; RESULT-FALSE: store i32 0, ptr null, align 4
+; RESULT-FALSE-NEXT: br label %bb2
+
+; RESULT-FALSE: bb1: ; No predecessors!
+; RESULT-FALSE-NEXT: store i32 1, ptr null, align 4
+; RESULT-FALSE-NEXT: br label %bb3
+define void @func(i1 %cond0, i1 %cond1) {
+bb0:
+ store i32 0, ptr null
+ br i1 %cond0, label %bb1, label %bb2
+
+bb1:
+ store i32 1, ptr null
+ br i1 %cond1, label %bb2, label %bb3
+
+bb2:
+ store i32 2, ptr null
+ br label %bb3
+
+bb3:
+ ret void
+}
diff --git a/llvm/tools/llvm-reduce/DeltaManager.cpp b/llvm/tools/llvm-reduce/DeltaManager.cpp
index 048a83c5e75d..ee29b44f531e 100644
--- a/llvm/tools/llvm-reduce/DeltaManager.cpp
+++ b/llvm/tools/llvm-reduce/DeltaManager.cpp
@@ -74,6 +74,8 @@ static cl::list<std::string>
DELTA_PASS("function-bodies", reduceFunctionBodiesDeltaPass) \
DELTA_PASS("special-globals", reduceSpecialGlobalsDeltaPass) \
DELTA_PASS("aliases", reduceAliasesDeltaPass) \
+ DELTA_PASS("simplify-conditionals-true", reduceConditionalsTrueDeltaPass) \
+ DELTA_PASS("simplify-conditionals-false", reduceConditionalsFalseDeltaPass)\
DELTA_PASS("basic-blocks", reduceBasicBlocksDeltaPass) \
DELTA_PASS("global-values", reduceGlobalValuesDeltaPass) \
DELTA_PASS("global-objects", reduceGlobalObjectsDeltaPass) \
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.cpp b/llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.cpp
index a45d57128a93..416b1652eb99 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.cpp
@@ -13,6 +13,8 @@
#include "ReduceUsingSimplifyCFG.h"
#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
@@ -31,3 +33,37 @@ static void reduceUsingSimplifyCFG(Oracle &O, Module &Program) {
void llvm::reduceUsingSimplifyCFGDeltaPass(TestRunner &Test) {
runDeltaPass(Test, reduceUsingSimplifyCFG, "Reducing using SimplifyCFG");
}
+static void reduceConditionals(Oracle &O, Module &M, bool Direction) {
+ SmallVector<BasicBlock *, 16> ToSimplify;
+
+ for (auto &F : M) {
+ for (auto &BB : F) {
+ auto *BR = dyn_cast<BranchInst>(BB.getTerminator());
+ if (!BR || !BR->isConditional() || O.shouldKeep())
+ continue;
+
+ if (Direction)
+ BR->setCondition(ConstantInt::getTrue(BR->getContext()));
+ else
+ BR->setCondition(ConstantInt::getFalse(BR->getContext()));
+
+ ToSimplify.push_back(&BB);
+ }
+ }
+
+ TargetTransformInfo TTI(M.getDataLayout());
+ for (auto *BB : ToSimplify)
+ simplifyCFG(BB, TTI);
+}
+
+void llvm::reduceConditionalsTrueDeltaPass(TestRunner &Test) {
+ runDeltaPass(
+ Test, [](Oracle &O, Module &M) { reduceConditionals(O, M, true); },
+ "Reducing conditional branches to true");
+}
+
+void llvm::reduceConditionalsFalseDeltaPass(TestRunner &Test) {
+ runDeltaPass(
+ Test, [](Oracle &O, Module &M) { reduceConditionals(O, M, false); },
+ "Reducing conditional branches to false");
+}
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.h b/llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.h
index 56cd15a1a135..01a14602909b 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.h
+++ b/llvm/tools/llvm-reduce/deltas/ReduceUsingSimplifyCFG.h
@@ -18,6 +18,8 @@
namespace llvm {
void reduceUsingSimplifyCFGDeltaPass(TestRunner &Test);
+void reduceConditionalsTrueDeltaPass(TestRunner &Test);
+void reduceConditionalsFalseDeltaPass(TestRunner &Test);
} // namespace llvm
#endif
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