Index: llvm/include/llvm/Transforms/Scalar/GVN.h =================================================================== --- llvm/include/llvm/Transforms/Scalar/GVN.h +++ llvm/include/llvm/Transforms/Scalar/GVN.h @@ -71,6 +71,7 @@ struct GVNOptions { Optional AllowPRE = None; Optional AllowLoadPRE = None; + Optional AllowLoadInLoopPRE = None; Optional AllowMemDep = None; GVNOptions() = default; @@ -87,6 +88,11 @@ return *this; } + GVNOptions &setLoadInLoopPRE(bool LoadInLoopPRE) { + AllowLoadInLoopPRE = LoadInLoopPRE; + return *this; + } + /// Enables or disables use of MemDepAnalysis. GVNOptions &setMemDep(bool MemDep) { AllowMemDep = MemDep; @@ -122,6 +128,7 @@ bool isPREEnabled() const; bool isLoadPREEnabled() const; + bool isLoadInLoopPREEnabled() const; bool isMemDepEnabled() const; /// This class holds the mapping between values and value numbers. It is used Index: llvm/lib/Transforms/Scalar/GVN.cpp =================================================================== --- llvm/lib/Transforms/Scalar/GVN.cpp +++ llvm/lib/Transforms/Scalar/GVN.cpp @@ -99,6 +99,8 @@ static cl::opt GVNEnablePRE("enable-pre", cl::init(true), cl::Hidden); static cl::opt GVNEnableLoadPRE("enable-load-pre", cl::init(true)); +static cl::opt GVNEnableLoadInLoopPRE("enable-load-in-loop-pre", + cl::init(true)); static cl::opt GVNEnableMemDep("enable-gvn-memdep", cl::init(true)); // Maximum allowed recursion depth. @@ -616,6 +618,11 @@ bool GVN::isLoadPREEnabled() const { return Options.AllowLoadPRE.getValueOr(GVNEnableLoadPRE); } + +bool GVN::isLoadInLoopPREEnabled() const { + return Options.AllowLoadInLoopPRE.getValueOr(GVNEnableLoadInLoopPRE); +} + bool GVN::isMemDepEnabled() const { return Options.AllowMemDep.getValueOr(GVNEnableMemDep); } @@ -1396,6 +1403,9 @@ // Step 4: Eliminate partial redundancy. if (!isPREEnabled() || !isLoadPREEnabled()) return false; + if (!isLoadInLoopPREEnabled() && this->LI && + this->LI->getLoopFor(LI->getParent())) + return false; return PerformLoadPRE(LI, ValuesPerBlock, UnavailableBlocks); } Index: llvm/test/Transforms/GVN/PRE/pre-load-in-loop.ll =================================================================== --- /dev/null +++ llvm/test/Transforms/GVN/PRE/pre-load-in-loop.ll @@ -0,0 +1,45 @@ +; RUN: opt < %s -basicaa -gvn -enable-load-in-loop-pre=false -S | FileCheck %s +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64" + +;void test1(int N, double *G) { +; int j; +; for (j = 0; j < N - 1; j++) +; G[j] = G[j] + G[j+1]; +;} + +define void @test1(i32 %N, double* nocapture %G) nounwind ssp { +; CHECK-LABEL: @test1( +entry: + %0 = add i32 %N, -1 + %1 = icmp sgt i32 %0, 0 + br i1 %1, label %bb.nph, label %return + +bb.nph: + %tmp = zext i32 %0 to i64 + br label %bb + +; CHECK: bb.nph: +; CHECK-NOT: load double, double* +; CHECK: br label %bb + +bb: + %indvar = phi i64 [ 0, %bb.nph ], [ %tmp6, %bb ] + %tmp6 = add i64 %indvar, 1 + %scevgep = getelementptr double, double* %G, i64 %tmp6 + %scevgep7 = getelementptr double, double* %G, i64 %indvar + %2 = load double, double* %scevgep7, align 8 + %3 = load double, double* %scevgep, align 8 + %4 = fadd double %2, %3 + store double %4, double* %scevgep7, align 8 + %exitcond = icmp eq i64 %tmp6, %tmp + br i1 %exitcond, label %return, label %bb + +; Both loads should remain in the loop. +; CHECK: bb: +; CHECK: load double, double* +; CHECK: load double, double* +; CHECK: br i1 %exitcond + +return: + ret void +}