#include <algorithm>
using namespace llvm;
+/// Enable analysis of recursive PHI nodes.
+static cl::opt<bool> EnableRecPhiAnalysis("basicaa-recphi",
+ cl::Hidden, cl::init(false));
+
/// Cutoff after which to stop analysing a set of phi nodes potentially involved
/// in a cycle. Because we are analysing 'through' phi nodes we need to be
/// careful with value equivalence. We use reachability to make sure a value
SmallPtrSet<Value*, 4> UniqueSrc;
SmallVector<Value*, 4> V1Srcs;
+ bool isRecursive = false;
for (Value *PV1 : PN->incoming_values()) {
if (isa<PHINode>(PV1))
// If any of the source itself is a PHI, return MayAlias conservatively
// sides are PHI nodes. In which case, this is O(m x n) time where 'm'
// and 'n' are the number of PHI sources.
return MayAlias;
+
+ if (EnableRecPhiAnalysis)
+ if (GEPOperator *PV1GEP = dyn_cast<GEPOperator>(PV1)) {
+ // Check whether the incoming value is a GEP that advances the pointer
+ // result of this PHI node (e.g. in a loop). If this is the case, we
+ // would recurse and always get a MayAlias. Handle this case specially
+ // below.
+ if (PV1GEP->getPointerOperand() == PN && PV1GEP->getNumIndices() == 1 &&
+ isa<ConstantInt>(PV1GEP->idx_begin())) {
+ isRecursive = true;
+ continue;
+ }
+ }
+
if (UniqueSrc.insert(PV1).second)
V1Srcs.push_back(PV1);
}
+ // If this PHI node is recursive, set the size of the accessed memory to
+ // unknown to represent all the possible values the GEP could advance the
+ // pointer to.
+ if (isRecursive)
+ PNSize = MemoryLocation::UnknownSize;
+
AliasResult Alias = aliasCheck(V2, V2Size, V2AAInfo,
V1Srcs[0], PNSize, PNAAInfo);
+
// Early exit if the check of the first PHI source against V2 is MayAlias.
// Other results are not possible.
if (Alias == MayAlias)
--- /dev/null
+; RUN: opt < %s -basicaa -basicaa-recphi=1 -gvn -S | FileCheck %s
+;
+; Check that section->word_ofs doesn't get reloaded in every iteration of the
+; for loop.
+;
+; Code:
+;
+; typedef struct {
+; unsigned num_words;
+; unsigned word_ofs;
+; const unsigned *data;
+; } section_t;
+;
+;
+; void test2(const section_t * restrict section, unsigned * restrict dst) {;
+; while (section->data != NULL) {
+; const unsigned *src = section->data;
+; for (unsigned i=0; i < section->num_words; ++i) {
+; dst[section->word_ofs + i] = src[i];
+; }
+;
+; ++section;
+; }
+; }
+;
+
+; CHECK-LABEL: for.body:
+; CHECK-NOT: load i32, i32* %word_ofs
+
+%struct.section_t = type { i32, i32, i32* }
+
+define void @test2(%struct.section_t* noalias nocapture readonly %section, i32* noalias nocapture %dst) {
+entry:
+ %data13 = getelementptr inbounds %struct.section_t, %struct.section_t* %section, i32 0, i32 2
+ %0 = load i32*, i32** %data13, align 4
+ %cmp14 = icmp eq i32* %0, null
+ br i1 %cmp14, label %while.end, label %for.cond.preheader
+
+for.cond.preheader: ; preds = %entry, %for.end
+ %1 = phi i32* [ %6, %for.end ], [ %0, %entry ]
+ %section.addr.015 = phi %struct.section_t* [ %incdec.ptr, %for.end ], [ %section, %entry ]
+ %num_words = getelementptr inbounds %struct.section_t, %struct.section_t* %section.addr.015, i32 0, i32 0
+ %2 = load i32, i32* %num_words, align 4
+ %cmp211 = icmp eq i32 %2, 0
+ br i1 %cmp211, label %for.end, label %for.body.lr.ph
+
+for.body.lr.ph: ; preds = %for.cond.preheader
+ %word_ofs = getelementptr inbounds %struct.section_t, %struct.section_t* %section.addr.015, i32 0, i32 1
+ br label %for.body
+
+for.body: ; preds = %for.body.lr.ph, %for.body
+ %arrayidx.phi = phi i32* [ %1, %for.body.lr.ph ], [ %arrayidx.inc, %for.body ]
+ %i.012 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.body ]
+ %3 = load i32, i32* %arrayidx.phi, align 4
+ %4 = load i32, i32* %word_ofs, align 4
+ %add = add i32 %4, %i.012
+ %arrayidx3 = getelementptr inbounds i32, i32* %dst, i32 %add
+ store i32 %3, i32* %arrayidx3, align 4
+ %inc = add i32 %i.012, 1
+ %5 = load i32, i32* %num_words, align 4
+ %cmp2 = icmp ult i32 %inc, %5
+ %arrayidx.inc = getelementptr i32, i32* %arrayidx.phi, i32 1
+ br i1 %cmp2, label %for.body, label %for.end
+
+for.end: ; preds = %for.body, %for.cond.preheader
+ %incdec.ptr = getelementptr inbounds %struct.section_t, %struct.section_t* %section.addr.015, i32 1
+ %data = getelementptr inbounds %struct.section_t, %struct.section_t* %section.addr.015, i32 1, i32 2
+ %6 = load i32*, i32** %data, align 4
+ %cmp = icmp eq i32* %6, null
+ br i1 %cmp, label %while.end, label %for.cond.preheader
+
+while.end: ; preds = %for.end, %entry
+ ret void
+}
+