[llvm] r272014 - [LAA] Improve non-wrapping pointer detection by handling loop-invariant case.
Andrey Turetskiy via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 7 07:55:27 PDT 2016
Author: aturetsk
Date: Tue Jun 7 09:55:27 2016
New Revision: 272014
URL: http://llvm.org/viewvc/llvm-project?rev=272014&view=rev
Log:
[LAA] Improve non-wrapping pointer detection by handling loop-invariant case.
This fixes PR26314. This patch adds new helper “isNoWrap” with detection of
loop-invariant pointer case.
Patch by Roman Shirokiy.
Ref: https://llvm.org/bugs/show_bug.cgi?id=26314
Differential Revision: http://reviews.llvm.org/D17268
Added:
llvm/trunk/test/Analysis/LoopAccessAnalysis/multiple-strides-rt-memory-checks.ll
llvm/trunk/test/Transforms/LoopVectorize/multiple-strides-vectorization.ll
Modified:
llvm/trunk/lib/Analysis/LoopAccessAnalysis.cpp
Modified: llvm/trunk/lib/Analysis/LoopAccessAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/LoopAccessAnalysis.cpp?rev=272014&r1=272013&r2=272014&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/LoopAccessAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/LoopAccessAnalysis.cpp Tue Jun 7 09:55:27 2016
@@ -467,7 +467,7 @@ public:
/// (i.e. the pointers have computable bounds).
bool canCheckPtrAtRT(RuntimePointerChecking &RtCheck, ScalarEvolution *SE,
Loop *TheLoop, const ValueToValueMap &Strides,
- bool ShouldCheckStride = false);
+ bool ShouldCheckWrap = false);
/// \brief Goes over all memory accesses, checks whether a RT check is needed
/// and builds sets of dependent accesses.
@@ -551,10 +551,21 @@ static bool hasComputableBounds(Predicat
return AR->isAffine();
}
+/// \brief Check whether a pointer address cannot wrap.
+static bool isNoWrap(PredicatedScalarEvolution &PSE,
+ const ValueToValueMap &Strides, Value *Ptr, Loop *L) {
+ const SCEV *PtrScev = PSE.getSCEV(Ptr);
+ if (PSE.getSE()->isLoopInvariant(PtrScev, L))
+ return true;
+
+ int Stride = getPtrStride(PSE, Ptr, L, Strides);
+ return Stride == 1;
+}
+
bool AccessAnalysis::canCheckPtrAtRT(RuntimePointerChecking &RtCheck,
ScalarEvolution *SE, Loop *TheLoop,
const ValueToValueMap &StridesMap,
- bool ShouldCheckStride) {
+ bool ShouldCheckWrap) {
// Find pointers with computable bounds. We are going to use this information
// to place a runtime bound check.
bool CanDoRT = true;
@@ -589,8 +600,7 @@ bool AccessAnalysis::canCheckPtrAtRT(Run
if (hasComputableBounds(PSE, StridesMap, Ptr, TheLoop) &&
// When we run after a failing dependency check we have to make sure
// we don't have wrapping pointers.
- (!ShouldCheckStride ||
- getPtrStride(PSE, Ptr, TheLoop, StridesMap) == 1)) {
+ (!ShouldCheckWrap || isNoWrap(PSE, StridesMap, Ptr, TheLoop))) {
// The id of the dependence set.
unsigned DepId;
Added: llvm/trunk/test/Analysis/LoopAccessAnalysis/multiple-strides-rt-memory-checks.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/LoopAccessAnalysis/multiple-strides-rt-memory-checks.ll?rev=272014&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/LoopAccessAnalysis/multiple-strides-rt-memory-checks.ll (added)
+++ llvm/trunk/test/Analysis/LoopAccessAnalysis/multiple-strides-rt-memory-checks.ll Tue Jun 7 09:55:27 2016
@@ -0,0 +1,67 @@
+; RUN: opt -loop-accesses -analyze -S < %s | FileCheck %s
+
+; This is the test case from PR26314.
+; When we were retrying dependence checking with memchecks only,
+; the loop-invariant access in the inner loop was incorrectly determined to be wrapping
+; because it was not strided in the inner loop.
+
+; #define Z 32
+; typedef struct s {
+; int v1[Z];
+; int v2[Z];
+; int v3[Z][Z];
+; } s;
+;
+; void slow_function (s* const obj) {
+; for (int j=0; j<Z; j++) {
+; for (int k=0; k<Z; k++) {
+; int x = obj->v1[k] + obj->v2[j];
+; obj->v3[j][k] += x;
+; }
+; }
+; }
+
+; CHECK: function 'Test':
+; CHECK: .inner:
+; CHECK-NEXT: Memory dependences are safe
+; CHECK-NEXT: Dependences:
+; CHECK-NEXT: Run-time memory checks:
+; CHECK: Check 0:
+; CHECK: Check 1:
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.s = type { [32 x i32], [32 x i32], [32 x [32 x i32]] }
+
+define void @Test(%struct.s* nocapture %obj) #0 {
+ br label %.outer.preheader
+
+
+.outer.preheader:
+ %i = phi i64 [ 0, %0 ], [ %i.next, %.outer ]
+ %1 = getelementptr inbounds %struct.s, %struct.s* %obj, i64 0, i32 1, i64 %i
+ br label %.inner
+
+.exit:
+ ret void
+
+.outer:
+ %i.next = add nuw nsw i64 %i, 1
+ %exitcond.outer = icmp eq i64 %i.next, 32
+ br i1 %exitcond.outer, label %.exit, label %.outer.preheader
+
+.inner:
+ %j = phi i64 [ 0, %.outer.preheader ], [ %j.next, %.inner ]
+ %2 = getelementptr inbounds %struct.s, %struct.s* %obj, i64 0, i32 0, i64 %j
+ %3 = load i32, i32* %2
+ %4 = load i32, i32* %1
+ %5 = add nsw i32 %4, %3
+ %6 = getelementptr inbounds %struct.s, %struct.s* %obj, i64 0, i32 2, i64 %i, i64 %j
+ %7 = load i32, i32* %6
+ %8 = add nsw i32 %5, %7
+ store i32 %8, i32* %6
+ %j.next = add nuw nsw i64 %j, 1
+ %exitcond.inner = icmp eq i64 %j.next, 32
+ br i1 %exitcond.inner, label %.outer, label %.inner
+}
Added: llvm/trunk/test/Transforms/LoopVectorize/multiple-strides-vectorization.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/multiple-strides-vectorization.ll?rev=272014&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/multiple-strides-vectorization.ll (added)
+++ llvm/trunk/test/Transforms/LoopVectorize/multiple-strides-vectorization.ll Tue Jun 7 09:55:27 2016
@@ -0,0 +1,65 @@
+; RUN: opt -loop-vectorize -S < %s | FileCheck %s
+
+; This is the test case from PR26314.
+; When we were retrying dependence checking with memchecks only,
+; the loop-invariant access in the inner loop was incorrectly determined to be wrapping
+; because it was not strided in the inner loop.
+; Improved wrapping detection allows vectorization in the following case.
+
+; #define Z 32
+; typedef struct s {
+; int v1[Z];
+; int v2[Z];
+; int v3[Z][Z];
+; } s;
+;
+; void slow_function (s* const obj) {
+; for (int j=0; j<Z; j++) {
+; for (int k=0; k<Z; k++) {
+; int x = obj->v1[k] + obj->v2[j];
+; obj->v3[j][k] += x;
+; }
+; }
+; }
+
+; CHECK-LABEL: Test
+; CHECK: <4 x i64>
+; CHECK: <4 x i32>, <4 x i32>
+; CHECK: llvm.loop.vectorize.width
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.s = type { [32 x i32], [32 x i32], [32 x [32 x i32]] }
+
+define void @Test(%struct.s* nocapture %obj) #0 {
+ br label %.outer.preheader
+
+
+.outer.preheader:
+ %i = phi i64 [ 0, %0 ], [ %i.next, %.outer ]
+ %1 = getelementptr inbounds %struct.s, %struct.s* %obj, i64 0, i32 1, i64 %i
+ br label %.inner
+
+.exit:
+ ret void
+
+.outer:
+ %i.next = add nuw nsw i64 %i, 1
+ %exitcond.outer = icmp eq i64 %i.next, 32
+ br i1 %exitcond.outer, label %.exit, label %.outer.preheader
+
+.inner:
+ %j = phi i64 [ 0, %.outer.preheader ], [ %j.next, %.inner ]
+ %2 = getelementptr inbounds %struct.s, %struct.s* %obj, i64 0, i32 0, i64 %j
+ %3 = load i32, i32* %2
+ %4 = load i32, i32* %1
+ %5 = add nsw i32 %4, %3
+ %6 = getelementptr inbounds %struct.s, %struct.s* %obj, i64 0, i32 2, i64 %i, i64 %j
+ %7 = load i32, i32* %6
+ %8 = add nsw i32 %5, %7
+ store i32 %8, i32* %6
+ %j.next = add nuw nsw i64 %j, 1
+ %exitcond.inner = icmp eq i64 %j.next, 32
+ br i1 %exitcond.inner, label %.outer, label %.inner
+}
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