[SimplifyCFG] Select the first instruction that we can handle in passingValueIsAlwaysUndefined
#98802
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…singValueIsAlwaysUndefined`
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@llvm/pr-subscribers-llvm-transforms Author: DianQK (DianQK) ChangesFixes #98799. Full diff: https://github.com/llvm/llvm-project/pull/98802.diff 3 Files Affected:
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 3fa3c0f1f52b0..a743858855047 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -7573,13 +7573,25 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I, bool PtrValu
return false;
if (C->isNullValue() || isa<UndefValue>(C)) {
- // Only look at the first use, avoid hurting compile time with long uselists
- auto *Use = cast<Instruction>(*I->user_begin());
- // Bail out if Use is not in the same BB as I or Use == I or Use comes
- // before I in the block. The latter two can be the case if Use is a PHI
- // node.
- if (Use->getParent() != I->getParent() || Use == I || Use->comesBefore(I))
+ // Only look at the first use we can hanle, avoid hurting compile time with
+ // long uselists
+ auto FindUse = llvm::find_if(I->users(), [&I](auto *U) {
+ auto *Use = cast<Instruction>(U);
+ // Bail out if Use is not in the same BB as I or Use == I or Use comes
+ // before I in the block. The latter two can be the case if Use is a
+ // PHI node.
+ if (Use->getParent() != I->getParent() || Use == I || Use->comesBefore(I))
+ return false;
+ // Change this list when we want to add new instructions.
+ if (!isa<GetElementPtrInst>(Use) && !isa<ReturnInst>(Use) &&
+ !isa<BitCastInst>(Use) && !isa<LoadInst>(Use) &&
+ !isa<StoreInst>(Use) && !isa<AssumeInst>(Use) && !isa<CallBase>(Use))
+ return false;
+ return true;
+ });
+ if (FindUse == I->user_end())
return false;
+ auto *Use = cast<Instruction>(*FindUse);
// Now make sure that there are no instructions in between that can alter
// control flow (eg. calls)
diff --git a/llvm/test/Transforms/PhaseOrdering/pr98799-inline-simplifycfg-ub.ll b/llvm/test/Transforms/PhaseOrdering/pr98799-inline-simplifycfg-ub.ll
new file mode 100644
index 0000000000000..17073fa198202
--- /dev/null
+++ b/llvm/test/Transforms/PhaseOrdering/pr98799-inline-simplifycfg-ub.ll
@@ -0,0 +1,56 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=inline,simplifycfg -S | FileCheck --check-prefix=CUSTOM %s
+; RUN: opt < %s -O2 -S | FileCheck --check-prefix=O2 %s
+
+define internal ptr @bar(ptr %arg, i1 %arg1) {
+bb:
+ br i1 %arg1, label %bb4, label %bb2
+
+bb2:
+ %i = load ptr, ptr %arg, align 8
+ %i3 = getelementptr inbounds i8, ptr %i, i64 1
+ store ptr %i3, ptr %arg, align 8
+ br label %bb4
+
+bb4:
+ %i5 = phi ptr [ %i, %bb2 ], [ null, %bb ]
+ ret ptr %i5
+}
+
+define i32 @foo(ptr %arg, i1 %arg1) {
+; CUSTOM-LABEL: define i32 @foo(
+; CUSTOM-SAME: ptr [[ARG:%.*]], i1 [[ARG1:%.*]]) {
+; CUSTOM-NEXT: [[BB:.*:]]
+; CUSTOM-NEXT: [[TMP0:%.*]] = xor i1 [[ARG1]], true
+; CUSTOM-NEXT: call void @llvm.assume(i1 [[TMP0]])
+; CUSTOM-NEXT: [[I_I:%.*]] = load ptr, ptr [[ARG]], align 8
+; CUSTOM-NEXT: [[I3_I:%.*]] = getelementptr inbounds i8, ptr [[I_I]], i64 1
+; CUSTOM-NEXT: store ptr [[I3_I]], ptr [[ARG]], align 8
+; CUSTOM-NEXT: [[I2:%.*]] = icmp ne ptr [[I_I]], null
+; CUSTOM-NEXT: call void @llvm.assume(i1 [[I2]])
+; CUSTOM-NEXT: [[I3:%.*]] = load i32, ptr [[I_I]], align 4
+; CUSTOM-NEXT: ret i32 [[I3]]
+;
+; O2-LABEL: define i32 @foo(
+; O2-SAME: ptr nocapture [[ARG:%.*]], i1 [[ARG1:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
+; O2-NEXT: [[BB:.*:]]
+; O2-NEXT: [[TMP0:%.*]] = xor i1 [[ARG1]], true
+; O2-NEXT: tail call void @llvm.assume(i1 [[TMP0]])
+; O2-NEXT: [[I_I:%.*]] = load ptr, ptr [[ARG]], align 8, !nonnull [[META0:![0-9]+]], !noundef [[META0]]
+; O2-NEXT: [[I3_I:%.*]] = getelementptr inbounds i8, ptr [[I_I]], i64 1
+; O2-NEXT: store ptr [[I3_I]], ptr [[ARG]], align 8
+; O2-NEXT: [[I3:%.*]] = load i32, ptr [[I_I]], align 4
+; O2-NEXT: ret i32 [[I3]]
+;
+bb:
+ %i = call ptr @bar(ptr %arg, i1 %arg1)
+ %i2 = icmp ne ptr %i, null
+ call void @llvm.assume(i1 %i2)
+ %i3 = load i32, ptr %i, align 4
+ ret i32 %i3
+}
+
+declare void @llvm.assume(i1)
+;.
+; O2: [[META0]] = !{}
+;.
diff --git a/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll b/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
index ef2d3219cca9b..c4602e72ecbce 100644
--- a/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
+++ b/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
@@ -20,7 +20,7 @@ F:
define void @test2() personality ptr @__gxx_personality_v0 {
; CHECK-LABEL: @test2(
; CHECK-NEXT: entry:
-; CHECK-NEXT: call void @test2() #[[ATTR3:[0-9]+]]
+; CHECK-NEXT: call void @test2() #[[ATTR4:[0-9]+]]
; CHECK-NEXT: ret void
;
entry:
@@ -242,6 +242,8 @@ declare ptr @fn_nonnull_deref_arg(ptr nonnull dereferenceable(4) %p)
declare ptr @fn_nonnull_deref_or_null_arg(ptr nonnull dereferenceable_or_null(4) %p)
declare ptr @fn_nonnull_arg(ptr nonnull %p)
declare ptr @fn_noundef_arg(ptr noundef %p)
+declare ptr @fn_ptr_arg(ptr)
+declare ptr @fn_ptr_arg_nounwind_willreturn(ptr) nounwind willreturn
define void @test9(i1 %X, ptr %Y) {
; CHECK-LABEL: @test9(
@@ -855,10 +857,72 @@ exit:
ret i32 %res
}
+; From bb to bb5 is UB.
+define i32 @test9_null_user_order_1(ptr %arg, i1 %arg1, ptr %arg2) {
+; CHECK-LABEL: @test9_null_user_order_1(
+; CHECK-NEXT: bb:
+; CHECK-NEXT: [[TMP0:%.*]] = xor i1 [[ARG1:%.*]], true
+; CHECK-NEXT: call void @llvm.assume(i1 [[TMP0]])
+; CHECK-NEXT: [[I:%.*]] = load ptr, ptr [[ARG:%.*]], align 8
+; CHECK-NEXT: [[I4:%.*]] = getelementptr inbounds i8, ptr [[I]], i64 1
+; CHECK-NEXT: store ptr [[I4]], ptr [[ARG]], align 8
+; CHECK-NEXT: [[I7:%.*]] = load i32, ptr [[I]], align 4
+; CHECK-NEXT: [[I8:%.*]] = icmp ne ptr [[I]], [[ARG2:%.*]]
+; CHECK-NEXT: call void @fn_ptr_arg(i1 [[I8]])
+; CHECK-NEXT: ret i32 [[I7]]
+;
+bb:
+ br i1 %arg1, label %bb5, label %bb3
+
+bb3: ; preds = %bb
+ %i = load ptr, ptr %arg, align 8
+ %i4 = getelementptr inbounds i8, ptr %i, i64 1
+ store ptr %i4, ptr %arg, align 8
+ br label %bb5
+
+bb5: ; preds = %bb3, %bb
+ %i6 = phi ptr [ %i, %bb3 ], [ null, %bb ]
+ %i7 = load i32, ptr %i6, align 4
+ %i8 = icmp ne ptr %i6, %arg2
+ call void @fn_ptr_arg(i1 %i8)
+ ret i32 %i7
+}
+
+define i32 @test9_null_user_order_2(ptr %arg, i1 %arg1, ptr %arg2) {
+; CHECK-LABEL: @test9_null_user_order_2(
+; CHECK-NEXT: bb:
+; CHECK-NEXT: [[TMP0:%.*]] = xor i1 [[ARG1:%.*]], true
+; CHECK-NEXT: call void @llvm.assume(i1 [[TMP0]])
+; CHECK-NEXT: [[I:%.*]] = load ptr, ptr [[ARG:%.*]], align 8
+; CHECK-NEXT: [[I4:%.*]] = getelementptr inbounds i8, ptr [[I]], i64 1
+; CHECK-NEXT: store ptr [[I4]], ptr [[ARG]], align 8
+; CHECK-NEXT: [[I8:%.*]] = icmp ne ptr [[I]], [[ARG2:%.*]]
+; CHECK-NEXT: call void @fn_ptr_arg_nounwind_willreturn(i1 [[I8]])
+; CHECK-NEXT: [[I7:%.*]] = load i32, ptr [[I]], align 4
+; CHECK-NEXT: ret i32 [[I7]]
+;
+bb:
+ br i1 %arg1, label %bb5, label %bb3
+
+bb3: ; preds = %bb
+ %i = load ptr, ptr %arg, align 8
+ %i4 = getelementptr inbounds i8, ptr %i, i64 1
+ store ptr %i4, ptr %arg, align 8
+ br label %bb5
+
+bb5: ; preds = %bb3, %bb
+ %i6 = phi ptr [ %i, %bb3 ], [ null, %bb ]
+ %i8 = icmp ne ptr %i6, %arg2
+ call void @fn_ptr_arg_nounwind_willreturn(i1 %i8)
+ %i7 = load i32, ptr %i6, align 4
+ ret i32 %i7
+}
+
attributes #0 = { null_pointer_is_valid }
;.
; CHECK: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: write) }
; CHECK: attributes #[[ATTR1:[0-9]+]] = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
; CHECK: attributes #[[ATTR2:[0-9]+]] = { null_pointer_is_valid }
-; CHECK: attributes #[[ATTR3]] = { nounwind }
+; CHECK: attributes #[[ATTR3:[0-9]+]] = { nounwind willreturn }
+; CHECK: attributes #[[ATTR4]] = { nounwind }
;.
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dtcxzyw
reviewed
Jul 14, 2024
dtcxzyw
added a commit
to dtcxzyw/llvm-opt-benchmark
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Jul 14, 2024
dtcxzyw
reviewed
Jul 14, 2024
dtcxzyw
reviewed
Jul 14, 2024
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IR diff LGTM. I am running compile-time tests :) BTW, I think most of dead blocks are created by JumpThreading. Can we avoid this to further improve compilation time? |
I haven't read the JumpThreading code yet, if it can't be handled within it, perhaps we could create some sort of simple matching pattern to hand over to SimplifyCFG? |
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I can't reproduce the problem yet, can you provide a more detailed test step? # CMake project
clang++ -D_FILE_OFFSET_BITS=64 -DCMAKE_BOOTSTRAP -DCMake_HAVE_CXX_MAKE_UNIQUE=1 -DCMake_HAVE_CXX_FILESYSTEM=1 -I/home/dianqk/llvm/CMake/build/Bootstrap.cmk -I/home/dianqk/llvm/CMake/Source -I/home/dianqk/llvm/CMake/Source/LexerParser -I/home/dianqk/llvm/CMake/Utilities/std -I/home/dianqk/llvm/CMake/Utilities -c /home/dianqk/llvm/CMake/Source/cmGeneratorExpressionLexer.cxx -o cmGeneratorExpressionLexer.o -emit-llvm -O3 -Xclang -disable-llvm-passes
# cmake (stage 1)
cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=OFF -DBUILD_SHARED_LIBS=ON ...
# main branch
perf stat $LLVM_PROJECT/build-base/bin/opt -O2 cmGeneratorExpressionLexer.o --disable-output
339,409,679 instructions:u
# pr
perf stat $LLVM_PROJECT/build/bin/opt -O2 cmGeneratorExpressionLexer.o --disable-output
338,379,357 instructions:u
# b686e35ec
339,831,704 instructions:u |
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It's surprising that b686e35 is making things worse: https://llvm-compile-time-tracker.com/compare.php?from=057abc842e581d01ac0bff435d779e3f506440ad&to=b686e35ecd81ae76fc517d14e133d44ed7ff9f4b&stat=instructions:u. But this PR has not changed overall: https://llvm-compile-time-tracker.com/compare.php?from=181e4c6291c94a38c0ee89d2128f8d70b15d2d23&to=b686e35ecd81ae76fc517d14e133d44ed7ff9f4b&stat=instructions%3Au. |
Can you try with |
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Oops, I can reproduce it. b686e35 fixed. |
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Hmm, at least locally, I can't reproduce |
yuxuanchen1997
pushed a commit
that referenced
this pull request
Jul 25, 2024
…singValueIsAlwaysUndefined` (#98802) Summary: Fixes #98799. Test Plan: Reviewers: Subscribers: Tasks: Tags: Differential Revision: https://phabricator.intern.facebook.com/D60251495
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Fixes #98799.
Perf: https://llvm-compile-time-tracker.com/compare.php?from=181e4c6291c94a38c0ee89d2128f8d70b15d2d23&to=b686e35ecd81ae76fc517d14e133d44ed7ff9f4b&stat=instructions%3Au