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1; RUN: opt < %s -passes='early-cse<memssa>' -earlycse-debug-hash -verify-memoryssa -disable-output2; REQUIRES: asserts3 4target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"5target triple = "x86_64-unknown-linux-gnu"6 7; Tests below highlight scenarios where EarlyCSE does not preserve MemorySSA8; optimized accesses. Current MemorySSA verify will accept these.9 10; Test 1:11; AA cannot tell here that the last load does not alias the only store.12; The first two loads are a common expression, EarlyCSE removes the second one,13; and then AA can see that the last load is a Use(LoE). Hence not optimized as14; it claims. Note that if we replace the GEP indices 2 and 1, AA sees NoAlias15; for the last load, before CSE-ing the first 2 loads.16%struct.ImageParameters = type { i32, i32, i32 }17@img = external global ptr, align 818define void @test1_macroblock() {19entry:20 ; MemoryUse(LoE)21 %0 = load ptr, ptr @img, align 822 23 %Pos_2 = getelementptr inbounds %struct.ImageParameters, ptr %0, i64 0, i32 224 ; 1 = MemoryDef(LoE)25 store i32 undef, ptr %Pos_2, align 826 27 ; MemoryUse(LoE)28 %1 = load ptr, ptr @img, align 829 30 %Pos_1 = getelementptr inbounds %struct.ImageParameters, ptr %1, i64 0, i32 131 ; MemoryUse(1) MayAlias32 %2 = load i32, ptr %Pos_1, align 433 unreachable34}35 36; Test 2:37; EarlyCSE simplifies %string to undef. Def and Use used to be MustAlias, with38; undef they are NoAlias. The Use can be optimized further to LoE. We can39; de-optimize uses of replaced instructions, but in general this is not enough40; (see next tests).41%struct.TermS = type { i32, i32, i32, i32, i32, ptr }42define fastcc void @test2_term_string() {43entry:44 %string = getelementptr inbounds %struct.TermS, ptr undef, i64 0, i32 545 ; 1 = MemoryDef(LoE)46 store ptr undef, ptr %string, align 847 ; MemoryUse(1) MustAlias48 %0 = load ptr, ptr %string, align 849 unreachable50}51 52; Test 3:53; EarlyCSE simplifies %0 to undef. So the second Def now stores to undef.54; We now find the second load (Use(2) can be optimized further to LoE)55; When replacing instructions, we can deoptimize all uses of the replaced56; instruction and all uses of transitive accesses. However this does not stop57; MemorySSA from being tripped by AA (see test4).58%struct.Grammar = type { ptr, ptr, %struct.anon }59%struct.anon = type { i32, i32, ptr, [3 x ptr] }60%struct.Term = type { i32 }61 62define fastcc void @test3_term_string(ptr %g) {63entry:64 ; 1 = MemoryDef(LoE)65 store ptr undef, ptr undef, align 866 ; MemoryUse(LoE)67 %0 = load ptr, ptr undef, align 868 %arrayidx = getelementptr inbounds i8, ptr %0, i64 undef69 ; 2 = MemoryDef(1)70 store i8 0, ptr %arrayidx, align 171 %v = getelementptr inbounds %struct.Grammar, ptr %g, i64 0, i32 2, i32 272 ; MemoryUse(2) MayAlias73 %1 = load ptr, ptr %v, align 874 unreachable75}76 77; Test 4:78; Removing dead/unused instructions in if.then274 makes AA smarter. Before79; removal, it finds %4 MayAlias the store above. After removal this can be80; optimized to LoE. Hence after EarlyCSE, there is an access who claims is81; optimized and it can be optimized further.82 83; We can't escape such cases in general when relying on Alias Analysis.84; The only fail-safe way to actually preserve MemorySSA when removing or85; replacing instructions (i.e. get the *same* MemorySSA as if it was computed86; for the updated IR) is to recompute it from scratch. What we get now is still87; a correct update, but with accesses that claim to be optimized and can be88; optimized further if we were to re-run MemorySSA on the IR.89%struct.gnode.0.1.3.6.9.18.20.79 = type { i32, i32, i32, i32, i32, i32, i32, ptr }90@gnodeArray = external global ptr, align 891 92define void @test4_shortest(i1 %arg) {93entry:94 %exl.i = alloca [5 x i32], align 1695 br i1 %arg, label %if.then274, label %for.cond40496 97if.then274: ; preds = %if.end25698 %arrayidx.i = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 199 %arrayidx1.i = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 2100 %arrayidx2.i = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 3101 %arrayidx3.i = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 4102 %arrayidx.i1034 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 1103 %arrayidx1.i1035 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 2104 %arrayidx2.i1036 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 3105 %arrayidx3.i1037 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 4106 unreachable107 108for.cond404: ; preds = %if.end256109 %arrayidx.i960 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 1110 %arrayidx1.i961 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 2111 %arrayidx2.i962 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 3112 ; 1 = MemoryDef(LoE)113 store i32 undef, ptr %arrayidx2.i962, align 4114 %arrayidx3.i963 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 4115 116 ; MemoryUse(LoE)117 %0 = load ptr, ptr @gnodeArray, align 8118 %arrayidx6.i968 = getelementptr inbounds ptr, ptr %0, i64 undef119 ; MemoryUse(1) MayAlias120 %1 = load ptr, ptr %arrayidx6.i968, align 8121 br i1 %arg, label %for.cond26.preheader.i974, label %if.then20.for.body_crit_edge.i999122 123for.cond26.preheader.i974: ; preds = %if.then20.i996124 %arrayidx.i924 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 1125 %arrayidx1.i925 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 2126 %arrayidx2.i926 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 3127 %arrayidx3.i927 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 4128 unreachable129 130if.then20.for.body_crit_edge.i999: ; preds = %if.then20.i996131 %arrayidx9.phi.trans.insert.i997 = getelementptr inbounds [5 x i32], ptr %exl.i, i64 0, i64 undef132 unreachable133}134