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[InstCombine] Fix PR35618: Instcombine hangs on single minmax load bitcast. 

Summary:
If we have pattern `store (load(bitcast(select (cmp(V1, V2), &V1,
&V2)))), bitcast)`, but the load is used in other instructions, it leads
to looping in InstCombiner. Patch adds additional check that all users
of the load instructions are stores and then replaces all uses of load
instruction by the new one with new type.

Reviewers: RKSimon, spatel, majnemer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D41072

llvm-svn: 320407
This commit is contained in:
Alexey Bataev 2017-12-11 19:11:16 +00:00
parent ba874922a2
commit ec128ace8a
2 changed files with 47 additions and 2 deletions
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19
llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
View File

@ -1344,9 +1344,24 @@ bool removeBitcastsFromLoadStoreOnMinMax(InstCombiner &IC, StoreInst &SI) {
if (!isMinMaxWithLoads(LoadAddr))
return false;
if (!all_of(LI->users(), [LI](User *U) {
auto *SI = dyn_cast<StoreInst>(U);
return SI && SI->getPointerOperand() != LI &&
!SI->getPointerOperand()->isSwiftError();
}))
return false;
IC.Builder.SetInsertPoint(LI);
LoadInst *NewLI = combineLoadToNewType(
IC, *LI, LoadAddr->getType()->getPointerElementType());
combineStoreToNewValue(IC, SI, NewLI);
// Replace all the stores with stores of the newly loaded value.
for (auto *UI : LI->users()) {
auto *SI = cast<StoreInst>(UI);
IC.Builder.SetInsertPoint(SI);
combineStoreToNewValue(IC, *SI, NewLI);
IC.eraseInstFromFunction(*SI);
}
IC.eraseInstFromFunction(*LI);
return true;
}
@ -1375,7 +1390,7 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
return eraseInstFromFunction(SI);
if (removeBitcastsFromLoadStoreOnMinMax(*this, SI))
return eraseInstFromFunction(SI);
return nullptr;
// Replace GEP indices if possible.
if (Instruction *NewGEPI = replaceGEPIdxWithZero(*this, Ptr, SI)) {

30
llvm/test/Transforms/InstCombine/multiple-uses-load-bitcast-select.ll Normal file
View File

@ -0,0 +1,30 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S -data-layout="E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64" | FileCheck %s
define void @PR35618(i64* %st1, double* %st2) {
; CHECK-LABEL: @PR35618(
; CHECK-NEXT: [[Y1:%.*]] = alloca double, align 8
; CHECK-NEXT: [[Z1:%.*]] = alloca double, align 8
; CHECK-NEXT: [[LD1:%.*]] = load double, double* [[Y1]], align 8
; CHECK-NEXT: [[LD2:%.*]] = load double, double* [[Z1]], align 8
; CHECK-NEXT: [[TMP10:%.*]] = fcmp olt double [[LD1]], [[LD2]]
; CHECK-NEXT: [[TMP121:%.*]] = select i1 [[TMP10]], double [[LD1]], double [[LD2]]
; CHECK-NEXT: [[TMP1:%.*]] = bitcast i64* [[ST1:%.*]] to double*
; CHECK-NEXT: store double [[TMP121]], double* [[TMP1]], align 8
; CHECK-NEXT: store double [[TMP121]], double* [[ST2:%.*]], align 8
; CHECK-NEXT: ret void
;
%y1 = alloca double
%z1 = alloca double
%ld1 = load double, double* %y1
%ld2 = load double, double* %z1
%tmp10 = fcmp olt double %ld1, %ld2
%sel = select i1 %tmp10, double* %y1, double* %z1
%tmp11 = bitcast double* %sel to i64*
%tmp12 = load i64, i64* %tmp11
store i64 %tmp12, i64* %st1
%bc = bitcast double* %st2 to i64*
store i64 %tmp12, i64* %bc
ret void
}