[llvm-commits] [llvm] r169788 - in /llvm/trunk: lib/Analysis/BasicAliasAnalysis.cpp test/Analysis/BasicAA/phi-speculation.ll
Arnold Schwaighofer
arnolds at codeaurora.org
Mon Dec 10 15:02:41 PST 2012
Author: arnolds
Date: Mon Dec 10 17:02:41 2012
New Revision: 169788
URL: http://llvm.org/viewvc/llvm-project?rev=169788&view=rev
Log:
Optimistically analyse Phi cycles
Analyse Phis under the starting assumption that they are NoAlias. Recursively
look at their inputs.
If they MayAlias/MustAlias there must be an input that makes them so.
Addresses bug 14351.
Modified:
llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
llvm/trunk/test/Analysis/BasicAA/phi-speculation.ll
Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=169788&r1=169787&r2=169788&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Mon Dec 10 17:02:41 2012
@@ -1064,48 +1064,20 @@
Location(V2, V2Size, V2TBAAInfo));
if (PN > V2)
std::swap(Locs.first, Locs.second);
-
- // Find the first incoming phi value not from its parent.
- unsigned f = 0;
- while (PN->getIncomingBlock(f) == PN->getParent() &&
- f < PN->getNumIncomingValues()-1)
- ++f;
-
- AliasResult Alias =
- aliasCheck(PN->getIncomingValue(f), PNSize, PNTBAAInfo,
- PN2->getIncomingValueForBlock(PN->getIncomingBlock(f)),
- V2Size, V2TBAAInfo);
- if (Alias == MayAlias)
- return MayAlias;
-
- // If the first source of the PHI nodes NoAlias and the other inputs are
- // the PHI node itself through some amount of recursion this does not add
- // any new information so just return NoAlias.
- // bb:
- // ptr = ptr2 + 1
- // loop:
- // ptr_phi = phi [bb, ptr], [loop, ptr_plus_one]
- // ptr2_phi = phi [bb, ptr2], [loop, ptr2_plus_one]
- // ...
- // ptr_plus_one = gep ptr_phi, 1
- // ptr2_plus_one = gep ptr2_phi, 1
- // We assume for the recursion that the the phis (ptr_phi, ptr2_phi) do
- // not alias each other.
- bool ArePhisAssumedNoAlias = false;
- AliasResult OrigAliasResult = NoAlias;
- if (Alias == NoAlias) {
- // Pretend the phis do not alias.
- assert(AliasCache.count(Locs) &&
- "There must exist an entry for the phi node");
- OrigAliasResult = AliasCache[Locs];
- AliasCache[Locs] = NoAlias;
- ArePhisAssumedNoAlias = true;
- }
+ // Analyse the PHIs' inputs under the assumption that the PHIs are
+ // NoAlias.
+ // If the PHIs are May/MustAlias there must be (recursively) an input
+ // operand from outside the PHIs' cycle that is MayAlias/MustAlias or
+ // there must be an operation on the PHIs within the PHIs' value cycle
+ // that causes a MayAlias.
+ // Pretend the phis do not alias.
+ AliasResult Alias = NoAlias;
+ assert(AliasCache.count(Locs) &&
+ "There must exist an entry for the phi node");
+ AliasResult OrigAliasResult = AliasCache[Locs];
+ AliasCache[Locs] = NoAlias;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
- if (i == f)
- continue;
-
AliasResult ThisAlias =
aliasCheck(PN->getIncomingValue(i), PNSize, PNTBAAInfo,
PN2->getIncomingValueForBlock(PN->getIncomingBlock(i)),
@@ -1116,7 +1088,7 @@
}
// Reset if speculation failed.
- if (ArePhisAssumedNoAlias && Alias != NoAlias)
+ if (Alias != NoAlias)
AliasCache[Locs] = OrigAliasResult;
return Alias;
Modified: llvm/trunk/test/Analysis/BasicAA/phi-speculation.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/phi-speculation.ll?rev=169788&r1=169787&r2=169788&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/BasicAA/phi-speculation.ll (original)
+++ llvm/trunk/test/Analysis/BasicAA/phi-speculation.ll Mon Dec 10 17:02:41 2012
@@ -4,9 +4,9 @@
; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
; ptr_phi and ptr2_phi do not alias.
+; CHECK: test_noalias_1
; CHECK: NoAlias: i32* %ptr2_phi, i32* %ptr_phi
-
-define i32 @test_noalias(i32* %ptr2, i32 %count, i32* %coeff) {
+define i32 @test_noalias_1(i32* %ptr2, i32 %count, i32* %coeff) {
entry:
%ptr = getelementptr inbounds i32* %ptr2, i64 1
br label %while.body
@@ -31,3 +31,64 @@
the_exit:
ret i32 %add
}
+
+; CHECK: test_noalias_2
+; CHECK: NoAlias: i32* %ptr_outer_phi, i32* %ptr_outer_phi2
+; CHECK: NoAlias: i32* %ptr2_phi, i32* %ptr_phi
+define i32 @test_noalias_2(i32* %ptr2, i32 %count, i32* %coeff) {
+entry:
+ %ptr = getelementptr inbounds i32* %ptr2, i64 1
+ br label %outer.while.header
+
+outer.while.header:
+ %ptr_outer_phi = phi i32* [%ptr_inc_outer, %outer.while.backedge], [ %ptr, %entry]
+ %ptr_outer_phi2 = phi i32* [%ptr2_inc_outer, %outer.while.backedge], [ %ptr2, %entry]
+ %num.outer = phi i32 [ %count, %entry ], [ %dec.outer, %outer.while.backedge ]
+ br label %while.body
+
+while.body:
+ %num = phi i32 [ %count, %outer.while.header ], [ %dec, %while.body ]
+ %ptr_phi = phi i32* [ %ptr_outer_phi, %outer.while.header ], [ %ptr_inc, %while.body ]
+ %ptr2_phi = phi i32* [ %ptr_outer_phi2, %outer.while.header ], [ %ptr2_inc, %while.body ]
+ %result.09 = phi i32 [ 0 , %outer.while.header ], [ %add, %while.body ]
+ %dec = add nsw i32 %num, -1
+ %0 = load i32* %ptr_phi, align 4
+ store i32 %0, i32* %ptr2_phi, align 4
+ %1 = load i32* %coeff, align 4
+ %2 = load i32* %ptr_phi, align 4
+ %mul = mul nsw i32 %1, %2
+ %add = add nsw i32 %mul, %result.09
+ %tobool = icmp eq i32 %dec, 0
+ %ptr_inc = getelementptr inbounds i32* %ptr_phi, i64 1
+ %ptr2_inc = getelementptr inbounds i32* %ptr2_phi, i64 1
+ br i1 %tobool, label %outer.while.backedge, label %while.body
+
+outer.while.backedge:
+ %ptr_inc_outer = getelementptr inbounds i32* %ptr_phi, i64 1
+ %ptr2_inc_outer = getelementptr inbounds i32* %ptr2_phi, i64 1
+ %dec.outer = add nsw i32 %num.outer, -1
+ %br.cond = icmp eq i32 %dec.outer, 0
+ br i1 %br.cond, label %the_exit, label %outer.while.header
+
+the_exit:
+ ret i32 %add
+}
+
+; CHECK: test_noalias_3
+; CHECK: MayAlias: i8* %ptr2_phi, i8* %ptr_phi
+define i32 @test_noalias_3(i8* noalias %x, i8* noalias %y, i8* noalias %z,
+ i32 %count) {
+entry:
+ br label %while.body
+
+while.body:
+ %num = phi i32 [ %count, %entry ], [ %dec, %while.body ]
+ %ptr_phi = phi i8* [ %x, %entry ], [ %z, %while.body ]
+ %ptr2_phi = phi i8* [ %y, %entry ], [ %ptr_phi, %while.body ]
+ %dec = add nsw i32 %num, -1
+ %tobool = icmp eq i32 %dec, 0
+ br i1 %tobool, label %the_exit, label %while.body
+
+the_exit:
+ ret i32 1
+}
More information about the llvm-commits
mailing list