[llvm] 56f7de5 - [InstCombine] Remove trivially empty ranges from end
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 26 11:04:45 PST 2020
Author: Nikita Popov
Date: 2020-02-26T20:04:11+01:00
New Revision: 56f7de5baae3ae9a746ac8f5a8e32cfcaf7b4a6b
URL: https://github.com/llvm/llvm-project/commit/56f7de5baae3ae9a746ac8f5a8e32cfcaf7b4a6b
DIFF: https://github.com/llvm/llvm-project/commit/56f7de5baae3ae9a746ac8f5a8e32cfcaf7b4a6b.diff
LOG: [InstCombine] Remove trivially empty ranges from end
InstCombine removes pairs of start+end intrinsics that don't
have anything in between them. Currently this is done by starting
at the start intrinsic and scanning forwards. This patch changes
it to start at the end intrinsic and scan backwards.
The motivation here is as follows: When we process the start
intrinsic, we have not yet looked at the following instructions,
which may still get folded/removed. If they do, we will only be
able to remove the start/end pair on the next iteration. When we
process the end intrinsic, all the instructions before it have
already been visited, and we don't run into this problem.
Differential Revision: https://reviews.llvm.org/D75011
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
llvm/lib/Transforms/InstCombine/InstCombineInternal.h
llvm/test/Transforms/InstCombine/lifetime.ll
llvm/test/Transforms/InstCombine/vararg.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index b542b363f6f2..7bd8bc4f4ccb 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1473,24 +1473,30 @@ static bool haveSameOperands(const IntrinsicInst &I, const IntrinsicInst &E,
// start/end intrinsics in between). As this handles only the most trivial
// cases, tracking the nesting level is not needed:
//
-// call @llvm.foo.start(i1 0) ; &I
// call @llvm.foo.start(i1 0)
-// call @llvm.foo.end(i1 0) ; This one will not be skipped: it will be removed
+// call @llvm.foo.start(i1 0) ; This one won't be skipped: it will be removed
// call @llvm.foo.end(i1 0)
-static bool removeTriviallyEmptyRange(IntrinsicInst &I, unsigned StartID,
- unsigned EndID, InstCombiner &IC) {
- assert(I.getIntrinsicID() == StartID &&
- "Start intrinsic does not have expected ID");
- BasicBlock::iterator BI(I), BE(I.getParent()->end());
- for (++BI; BI != BE; ++BI) {
- if (auto *E = dyn_cast<IntrinsicInst>(BI)) {
- if (isa<DbgInfoIntrinsic>(E) || E->getIntrinsicID() == StartID)
+// call @llvm.foo.end(i1 0) ; &I
+static bool removeTriviallyEmptyRange(
+ IntrinsicInst &EndI, InstCombiner &IC,
+ std::function<bool(const IntrinsicInst &)> IsStart) {
+ // We start from the end intrinsic and scan backwards, so that InstCombine
+ // has already processed (and potentially removed) all the instructions
+ // before the end intrinsic.
+ BasicBlock::reverse_iterator BI(EndI), BE(EndI.getParent()->rend());
+ for (; BI != BE; ++BI) {
+ if (auto *I = dyn_cast<IntrinsicInst>(&*BI)) {
+ if (isa<DbgInfoIntrinsic>(I) ||
+ I->getIntrinsicID() == EndI.getIntrinsicID())
+ continue;
+ if (IsStart(*I)) {
+ if (haveSameOperands(EndI, *I, EndI.getNumArgOperands())) {
+ IC.eraseInstFromFunction(*I);
+ IC.eraseInstFromFunction(EndI);
+ return true;
+ }
+ // Skip start intrinsics that don't pair with this end intrinsic.
continue;
- if (E->getIntrinsicID() == EndID &&
- haveSameOperands(I, *E, E->getNumArgOperands())) {
- IC.eraseInstFromFunction(*E);
- IC.eraseInstFromFunction(I);
- return true;
}
}
break;
@@ -1748,13 +1754,11 @@ static Instruction *SimplifyNVVMIntrinsic(IntrinsicInst *II, InstCombiner &IC) {
llvm_unreachable("All SpecialCase enumerators should be handled in switch.");
}
-Instruction *InstCombiner::visitVAStartInst(VAStartInst &I) {
- removeTriviallyEmptyRange(I, Intrinsic::vastart, Intrinsic::vaend, *this);
- return nullptr;
-}
-
-Instruction *InstCombiner::visitVACopyInst(VACopyInst &I) {
- removeTriviallyEmptyRange(I, Intrinsic::vacopy, Intrinsic::vaend, *this);
+Instruction *InstCombiner::visitVAEndInst(VAEndInst &I) {
+ removeTriviallyEmptyRange(I, *this, [](const IntrinsicInst &I) {
+ return I.getIntrinsicID() == Intrinsic::vastart ||
+ I.getIntrinsicID() == Intrinsic::vacopy;
+ });
return nullptr;
}
@@ -4056,7 +4060,7 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
return eraseInstFromFunction(CI);
break;
}
- case Intrinsic::lifetime_start:
+ case Intrinsic::lifetime_end:
// Asan needs to poison memory to detect invalid access which is possible
// even for empty lifetime range.
if (II->getFunction()->hasFnAttribute(Attribute::SanitizeAddress) ||
@@ -4064,8 +4068,9 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
II->getFunction()->hasFnAttribute(Attribute::SanitizeHWAddress))
break;
- if (removeTriviallyEmptyRange(*II, Intrinsic::lifetime_start,
- Intrinsic::lifetime_end, *this))
+ if (removeTriviallyEmptyRange(*II, *this, [](const IntrinsicInst &I) {
+ return I.getIntrinsicID() == Intrinsic::lifetime_start;
+ }))
return nullptr;
break;
case Intrinsic::assume: {
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index 215183d9e109..f80da4395461 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -445,8 +445,7 @@ class LLVM_LIBRARY_VISIBILITY InstCombiner
Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
Instruction *visitExtractValueInst(ExtractValueInst &EV);
Instruction *visitLandingPadInst(LandingPadInst &LI);
- Instruction *visitVAStartInst(VAStartInst &I);
- Instruction *visitVACopyInst(VACopyInst &I);
+ Instruction *visitVAEndInst(VAEndInst &I);
Instruction *visitFreeze(FreezeInst &I);
/// Specify what to return for unhandled instructions.
diff --git a/llvm/test/Transforms/InstCombine/lifetime.ll b/llvm/test/Transforms/InstCombine/lifetime.ll
index 8eb6646c8410..4be8d83f2b7b 100644
--- a/llvm/test/Transforms/InstCombine/lifetime.ll
+++ b/llvm/test/Transforms/InstCombine/lifetime.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -instcombine -S | FileCheck %s
+; RUN: opt < %s -instcombine -instcombine-infinite-loop-threshold=2 -S | FileCheck %s
declare void @llvm.dbg.declare(metadata, metadata, metadata)
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
diff --git a/llvm/test/Transforms/InstCombine/vararg.ll b/llvm/test/Transforms/InstCombine/vararg.ll
index 111cb4de7bc3..8fc9aafcdefc 100644
--- a/llvm/test/Transforms/InstCombine/vararg.ll
+++ b/llvm/test/Transforms/InstCombine/vararg.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -instcombine -S | FileCheck %s
+; RUN: opt < %s -instcombine -instcombine-infinite-loop-threshold=2 -S | FileCheck %s
%struct.__va_list = type { i8*, i8*, i8*, i32, i32 }
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