[llvm] 9aa1428 - [InstSimplify] Treat invariant group insts as bitcasts for load operands
Arthur Eubanks via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 15 12:59:58 PDT 2021
Author: Arthur Eubanks
Date: 2021-06-15T12:59:43-07:00
New Revision: 9aa1428174ae5d0515f49d50a483a5517f4df2f4
URL: https://github.com/llvm/llvm-project/commit/9aa1428174ae5d0515f49d50a483a5517f4df2f4
DIFF: https://github.com/llvm/llvm-project/commit/9aa1428174ae5d0515f49d50a483a5517f4df2f4.diff
LOG: [InstSimplify] Treat invariant group insts as bitcasts for load operands
We can look through invariant group intrinsics for the purposes of
simplifying the result of a load.
Since intrinsics can't be constants, but we also don't want to
completely rewrite load constant folding, we convert the load operand to
a constant. For GEPs and bitcasts we just treat them as constants. For
invariant group intrinsics, we treat them as a bitcast.
Relanding with a check for self-referential values.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D101103
Added:
llvm/test/Transforms/InstSimplify/invalid-load-operand-infinite-loop.ll
Modified:
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/test/Transforms/InstSimplify/invariant.group-load.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 2e591bb8df5c..7fb7a394e86a 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -18,6 +18,7 @@
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
@@ -5823,6 +5824,78 @@ Value *llvm::SimplifyFreezeInst(Value *Op0, const SimplifyQuery &Q) {
return ::SimplifyFreezeInst(Op0, Q);
}
+static Constant *ConstructLoadOperandConstant(Value *Op) {
+ SmallVector<Value *, 4> Worklist;
+ // Invalid IR in unreachable code may contain self-referential values. Don't infinitely loop.
+ SmallPtrSet<Value *, 4> Visited;
+ Worklist.push_back(Op);
+ while (true) {
+ Value *CurOp = Worklist.back();
+ if (!Visited.insert(CurOp).second)
+ return nullptr;
+ if (isa<Constant>(CurOp))
+ break;
+ if (auto *BC = dyn_cast<BitCastOperator>(CurOp)) {
+ Worklist.push_back(BC->getOperand(0));
+ } else if (auto *GEP = dyn_cast<GEPOperator>(CurOp)) {
+ for (unsigned I = 1; I != GEP->getNumOperands(); ++I) {
+ if (!isa<Constant>(GEP->getOperand(I)))
+ return nullptr;
+ }
+ Worklist.push_back(GEP->getOperand(0));
+ } else if (auto *II = dyn_cast<IntrinsicInst>(CurOp)) {
+ if (II->isLaunderOrStripInvariantGroup())
+ Worklist.push_back(II->getOperand(0));
+ else
+ return nullptr;
+ } else {
+ return nullptr;
+ }
+ }
+
+ Constant *NewOp = cast<Constant>(Worklist.pop_back_val());
+ while (!Worklist.empty()) {
+ Value *CurOp = Worklist.pop_back_val();
+ if (isa<BitCastOperator>(CurOp)) {
+ NewOp = ConstantExpr::getBitCast(NewOp, CurOp->getType());
+ } else if (auto *GEP = dyn_cast<GEPOperator>(CurOp)) {
+ SmallVector<Constant *> Idxs;
+ Idxs.reserve(GEP->getNumOperands() - 1);
+ for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I) {
+ Idxs.push_back(cast<Constant>(GEP->getOperand(I)));
+ }
+ NewOp = ConstantExpr::getGetElementPtr(GEP->getSourceElementType(), NewOp,
+ Idxs, GEP->isInBounds(),
+ GEP->getInRangeIndex());
+ } else {
+ assert(isa<IntrinsicInst>(CurOp) &&
+ cast<IntrinsicInst>(CurOp)->isLaunderOrStripInvariantGroup() &&
+ "expected invariant group intrinsic");
+ NewOp = ConstantExpr::getBitCast(NewOp, CurOp->getType());
+ }
+ }
+ return NewOp;
+}
+
+static Value *SimplifyLoadInst(LoadInst *LI, const SimplifyQuery &Q) {
+ if (LI->isVolatile())
+ return nullptr;
+
+ if (auto *C = ConstantFoldInstruction(LI, Q.DL))
+ return C;
+
+ // The following only catches more cases than ConstantFoldInstruction() if the
+ // load operand wasn't a constant. Specifically, invariant.group intrinsics.
+ if (isa<Constant>(LI->getPointerOperand()))
+ return nullptr;
+
+ if (auto *C = dyn_cast_or_null<Constant>(
+ ConstructLoadOperandConstant(LI->getPointerOperand())))
+ return ConstantFoldLoadFromConstPtr(C, LI->getType(), Q.DL);
+
+ return nullptr;
+}
+
/// See if we can compute a simplified version of this instruction.
/// If not, this returns null.
@@ -5979,6 +6052,9 @@ Value *llvm::SimplifyInstruction(Instruction *I, const SimplifyQuery &SQ,
// No simplifications for Alloca and it can't be constant folded.
Result = nullptr;
break;
+ case Instruction::Load:
+ Result = SimplifyLoadInst(cast<LoadInst>(I), Q);
+ break;
}
/// If called on unreachable code, the above logic may report that the
diff --git a/llvm/test/Transforms/InstSimplify/invalid-load-operand-infinite-loop.ll b/llvm/test/Transforms/InstSimplify/invalid-load-operand-infinite-loop.ll
new file mode 100644
index 000000000000..6a4fe2686117
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/invalid-load-operand-infinite-loop.ll
@@ -0,0 +1,51 @@
+; RUN: opt -passes=jump-threading -S < %s | FileCheck %s
+; CHECK: @main
+
+%struct.wobble = type { i8 }
+
+define i32 @main() local_unnamed_addr personality i8* undef {
+bb12:
+ br i1 false, label %bb13, label %bb28
+
+bb13: ; preds = %bb12
+ br label %bb14
+
+bb14: ; preds = %bb26, %bb13
+ %tmp15 = phi i8* [ %tmp27, %bb26 ], [ undef, %bb13 ]
+ %tmp16 = icmp slt i32 5, undef
+ %tmp17 = select i1 false, i1 true, i1 %tmp16
+ br label %bb18
+
+bb18: ; preds = %bb14
+ br i1 %tmp17, label %bb19, label %bb21
+
+bb19: ; preds = %bb18
+ %tmp20 = or i32 undef, 4
+ br label %bb21
+
+bb21: ; preds = %bb19, %bb18
+ %tmp22 = load i8, i8* %tmp15, align 1
+ br label %bb23
+
+bb23: ; preds = %bb21
+ br i1 %tmp17, label %bb24, label %bb25
+
+bb24: ; preds = %bb23
+ br label %bb25
+
+bb25: ; preds = %bb24, %bb23
+ invoke void undef(%struct.wobble* undef, i32 0, i32 undef, i8 %tmp22)
+ to label %bb26 unwind label %bb33
+
+bb26: ; preds = %bb25
+ %tmp27 = getelementptr inbounds i8, i8* %tmp15, i64 1
+ br label %bb14
+
+bb28: ; preds = %bb12
+ unreachable
+
+bb33: ; preds = %bb25
+ %tmp34 = landingpad { i8*, i32 }
+ cleanup
+ unreachable
+}
diff --git a/llvm/test/Transforms/InstSimplify/invariant.group-load.ll b/llvm/test/Transforms/InstSimplify/invariant.group-load.ll
index 72cb36d2eee6..f1ee1528e8ac 100644
--- a/llvm/test/Transforms/InstSimplify/invariant.group-load.ll
+++ b/llvm/test/Transforms/InstSimplify/invariant.group-load.ll
@@ -9,11 +9,7 @@ declare i8* @llvm.launder.invariant.group.p0i8(i8* %p)
define i64 @f() {
; CHECK-LABEL: @f(
-; CHECK-NEXT: [[A:%.*]] = call i8* @llvm.strip.invariant.group.p0i8(i8* bitcast ({ i64, i64 }* @A to i8*))
-; CHECK-NEXT: [[B:%.*]] = getelementptr i8, i8* [[A]], i32 8
-; CHECK-NEXT: [[C:%.*]] = bitcast i8* [[B]] to i64*
-; CHECK-NEXT: [[D:%.*]] = load i64, i64* [[C]], align 4
-; CHECK-NEXT: ret i64 [[D]]
+; CHECK-NEXT: ret i64 3
;
%p = bitcast { i64, i64 }* @A to i8*
%a = call i8* @llvm.strip.invariant.group.p0i8(i8* %p)
@@ -25,11 +21,7 @@ define i64 @f() {
define i64 @g() {
; CHECK-LABEL: @g(
-; CHECK-NEXT: [[A:%.*]] = call i8* @llvm.launder.invariant.group.p0i8(i8* bitcast ({ i64, i64 }* @A to i8*))
-; CHECK-NEXT: [[B:%.*]] = getelementptr i8, i8* [[A]], i32 8
-; CHECK-NEXT: [[C:%.*]] = bitcast i8* [[B]] to i64*
-; CHECK-NEXT: [[D:%.*]] = load i64, i64* [[C]], align 4
-; CHECK-NEXT: ret i64 [[D]]
+; CHECK-NEXT: ret i64 3
;
%p = bitcast { i64, i64 }* @A to i8*
%a = call i8* @llvm.launder.invariant.group.p0i8(i8* %p)
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