[ValueTracking] isNonEqual Pointers with with a recursive GEP #70459
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@llvm/pr-subscribers-llvm-transforms @llvm/pr-subscribers-llvm-analysis Author: None (bipmis) ChangesHandles canonical icmp eq(ptr1, ptr2) -> where ptr1/ptr2 is a recursive GEP. Patch is 22.45 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/70459.diff 3 Files Affected:
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index c303d261107eb19..1fd4ce496fcae9f 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -3141,6 +3141,72 @@ static bool isNonEqualSelect(const Value *V1, const Value *V2, unsigned Depth,
isKnownNonEqual(SI1->getFalseValue(), V2, Depth + 1, Q);
}
+static bool isNonEqualPointersWithRecursiveGEP(const Value *A, const Value *B,
+ unsigned Depth,
+ const SimplifyQuery &Q) {
+ // Where A is a recursive GEP for an incoming value of PHI indicating a
+ // loop. B can be a ptr/GEP.
+ // If the PHI has 2 incoming values, one of it being the recursive GEP A
+ // and other a ptr at same base and at an same/higher offset than B we are
+ // only incrementing the pointer further in loop if offset of recursive GEP is
+ // greater than 0.
+ if (!A->getType()->isPointerTy() || !B->getType()->isPointerTy())
+ return false;
+
+ auto *GEPA = dyn_cast<GEPOperator>(A);
+ // Make sure GEPA pointer operand is a PHI.
+ if (!GEPA || !isa<PHINode>(GEPA->getPointerOperand()))
+ return false;
+
+ // Handle 2 incoming PHI values with one being a recursive GEP.
+ auto *PN = dyn_cast<PHINode>(GEPA->getPointerOperand());
+ if (PN->getNumIncomingValues() == 2) {
+ // Recursive GEP in second incoming value. Always keep Recursive GEP as
+ // FirstInst
+ Value *FirstInst = nullptr, *SecondInst = nullptr;
+ for (unsigned i = 0; i != 2; ++i) {
+ // Check if A is a Recursive GEP in one of the incoming values.
+ if (PN->getIncomingValue(i) == A && GEPA->getNumIndices() == 1 &&
+ isa<Constant>(GEPA->idx_begin())) {
+ FirstInst = PN->getIncomingValue(i);
+ SecondInst = PN->getIncomingValue(1 - i);
+ continue;
+ }
+ }
+ if (FirstInst && SecondInst) {
+ // Other incoming node base should match the B base.
+ // SecondInstOffset >= OffsetB && FirstInstOffset > 0?
+ // SecondInstOffset <= OffsetB && FirstInstOffset < 0?
+ // Is non-equal if above are true.
+ APInt FirstInstOffset(Q.DL.getIndexTypeSizeInBits(FirstInst->getType()),
+ 0);
+ FirstInst = FirstInst->stripAndAccumulateConstantOffsets(
+ Q.DL, FirstInstOffset, /* AllowNonInbounds */ true);
+ APInt SecondInstOffset(Q.DL.getIndexTypeSizeInBits(SecondInst->getType()),
+ 0);
+ SecondInst = SecondInst->stripAndAccumulateConstantOffsets(
+ Q.DL, SecondInstOffset, /* AllowNonInbounds */ true);
+ APInt OffsetB(Q.DL.getIndexTypeSizeInBits(B->getType()), 0);
+ B = B->stripAndAccumulateConstantOffsets(Q.DL, OffsetB,
+ /* AllowNonInbounds */ true);
+ if (SecondInst == B &&
+ ((SecondInstOffset.sge(OffsetB) && FirstInstOffset.sgt(0)) ||
+ (SecondInstOffset.sle(OffsetB) && FirstInstOffset.slt(0))))
+ return true;
+ }
+ }
+ return false;
+}
+
+static bool isNonEqualPointers(const Value *V1, const Value *V2, unsigned Depth,
+ const SimplifyQuery &Q) {
+ // Check if A is a recursive GEP which is not equal to B.
+ if (isNonEqualPointersWithRecursiveGEP(V1, V2, Depth, Q))
+ return true;
+
+ return false;
+}
+
/// Return true if it is known that V1 != V2.
static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
const SimplifyQuery &Q) {
@@ -3194,6 +3260,10 @@ static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
if (isNonEqualSelect(V1, V2, Depth, Q) || isNonEqualSelect(V2, V1, Depth, Q))
return true;
+ if (isNonEqualPointers(V1, V2, Depth, Q) ||
+ isNonEqualPointers(V2, V1, Depth, Q))
+ return true;
+
return false;
}
diff --git a/llvm/test/Analysis/ValueTracking/known-non-equal.ll b/llvm/test/Analysis/ValueTracking/known-non-equal.ll
index 79b9b3fd8511b60..365a0ea9bc21dbb 100644
--- a/llvm/test/Analysis/ValueTracking/known-non-equal.ll
+++ b/llvm/test/Analysis/ValueTracking/known-non-equal.ll
@@ -1813,5 +1813,42 @@ exit:
ret i1 %res
}
+; Illustrate if 2 pointers are non-equal when one of them is a recursive GEP.
+define i1 @icmp_recursiveGEP_withPtr(ptr noundef %val1) {
+; CHECK-LABEL: @icmp_recursiveGEP_withPtr(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp eq ptr [[VAL1:%.*]], null
+; CHECK-NEXT: br i1 [[CMP_I]], label [[_Z9STRINGLENPKS_EXIT:%.*]], label [[WHILE_COND_I:%.*]]
+; CHECK: while.cond.i:
+; CHECK-NEXT: [[A_PN_I:%.*]] = phi ptr [ [[TEST_0_I:%.*]], [[WHILE_COND_I]] ], [ [[VAL1]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TEST_0_I]] = getelementptr inbounds i8, ptr [[A_PN_I]], i64 1
+; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[TEST_0_I]], align 2
+; CHECK-NEXT: [[CMP3_NOT_I:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[CMP3_NOT_I]], label [[WHILE_END_I:%.*]], label [[WHILE_COND_I]]
+; CHECK: while.end.i:
+; CHECK-NEXT: br label [[_Z9STRINGLENPKS_EXIT]]
+; CHECK: _Z9stringlenPKs.exit:
+; CHECK-NEXT: [[RETVAL_0_I:%.*]] = phi i1 [ false, [[WHILE_END_I]] ], [ true, [[ENTRY]] ]
+; CHECK-NEXT: ret i1 [[RETVAL_0_I]]
+;
+entry:
+ %cmp.i = icmp eq ptr %val1, null
+ br i1 %cmp.i, label %_Z9stringlenPKs.exit, label %while.cond.i
+
+while.cond.i:
+ %a.pn.i = phi ptr [ %test.0.i, %while.cond.i ], [ %val1, %entry ]
+ %test.0.i = getelementptr inbounds i8, ptr %a.pn.i, i64 1
+ %0 = load i8, ptr %test.0.i, align 2
+ %cmp3.not.i = icmp eq i8 %0, 0
+ br i1 %cmp3.not.i, label %while.end.i, label %while.cond.i
+
+while.end.i:
+ %bool = icmp eq ptr %test.0.i, %val1
+ br label %_Z9stringlenPKs.exit
+
+_Z9stringlenPKs.exit:
+ %retval.0.i = phi i1 [ %bool, %while.end.i ], [ true, %entry ]
+ ret i1 %retval.0.i
+}
!0 = !{ i8 1, i8 5 }
diff --git a/llvm/test/Analysis/ValueTracking/phi-known-bits.ll b/llvm/test/Analysis/ValueTracking/phi-known-bits.ll
index 5227661c837347e..1fed11792f13521 100644
--- a/llvm/test/Analysis/ValueTracking/phi-known-bits.ll
+++ b/llvm/test/Analysis/ValueTracking/phi-known-bits.ll
@@ -424,3 +424,373 @@ T:
F:
br label %T
}
+
+;Illustrate if 2 pointers are non-equal when one of them is a recursive GEP.
+;Cases which folds to a canonical icmp(ptr1, ptr2)
+define i1 @recursiveGEP_withPtr_phisub1(ptr noundef %val1) {
+; CHECK-LABEL: @recursiveGEP_withPtr_phisub1(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp eq ptr [[VAL1:%.*]], null
+; CHECK-NEXT: br i1 [[CMP_I]], label [[_Z9STRINGLENPKS_EXIT:%.*]], label [[WHILE_COND_I:%.*]]
+; CHECK: while.cond.i:
+; CHECK-NEXT: [[A_PN_I:%.*]] = phi ptr [ [[TEST_0_I:%.*]], [[WHILE_COND_I]] ], [ [[VAL1]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TEST_0_I]] = getelementptr inbounds i8, ptr [[A_PN_I]], i64 1
+; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[TEST_0_I]], align 2
+; CHECK-NEXT: [[CMP3_NOT_I:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[CMP3_NOT_I]], label [[WHILE_END_I:%.*]], label [[WHILE_COND_I]]
+; CHECK: while.end.i:
+; CHECK-NEXT: br label [[_Z9STRINGLENPKS_EXIT]]
+; CHECK: _Z9stringlenPKs.exit:
+; CHECK-NEXT: ret i1 [[CMP_I]]
+;
+entry:
+ %cmp.i = icmp eq ptr %val1, null
+ br i1 %cmp.i, label %_Z9stringlenPKs.exit, label %while.cond.i
+
+while.cond.i:
+ %a.pn.i = phi ptr [ %test.0.i, %while.cond.i ], [ %val1, %entry ]
+ %test.0.i = getelementptr inbounds i8, ptr %a.pn.i, i64 1
+ %0 = load i8, ptr %test.0.i, align 2
+ %cmp3.not.i = icmp eq i8 %0, 0
+ br i1 %cmp3.not.i, label %while.end.i, label %while.cond.i
+
+while.end.i:
+ %sub.ptr.lhs.cast.i = ptrtoint ptr %test.0.i to i64
+ %sub.ptr.rhs.cast.i = ptrtoint ptr %val1 to i64
+ %sub.ptr.sub.i = sub i64 %sub.ptr.lhs.cast.i, %sub.ptr.rhs.cast.i
+ br label %_Z9stringlenPKs.exit
+
+_Z9stringlenPKs.exit:
+ %retval.0.i = phi i64 [ %sub.ptr.sub.i, %while.end.i ], [ 0, %entry ]
+ %bool = icmp eq i64 %retval.0.i, 0
+ ret i1 %bool
+}
+
+define i1 @recursiveGEP_withPtr_phisub1_PhiOperandsCommuted(ptr noundef %val1) {
+; CHECK-LABEL: @recursiveGEP_withPtr_phisub1_PhiOperandsCommuted(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp eq ptr [[VAL1:%.*]], null
+; CHECK-NEXT: br i1 [[CMP_I]], label [[_Z9STRINGLENPKS_EXIT:%.*]], label [[WHILE_COND_I:%.*]]
+; CHECK: while.cond.i:
+; CHECK-NEXT: [[A_PN_I:%.*]] = phi ptr [ [[VAL1]], [[ENTRY:%.*]] ], [ [[TEST_0_I:%.*]], [[WHILE_COND_I]] ]
+; CHECK-NEXT: [[TEST_0_I]] = getelementptr inbounds i8, ptr [[A_PN_I]], i64 1
+; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[TEST_0_I]], align 2
+; CHECK-NEXT: [[CMP3_NOT_I:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[CMP3_NOT_I]], label [[WHILE_END_I:%.*]], label [[WHILE_COND_I]]
+; CHECK: while.end.i:
+; CHECK-NEXT: br label [[_Z9STRINGLENPKS_EXIT]]
+; CHECK: _Z9stringlenPKs.exit:
+; CHECK-NEXT: ret i1 [[CMP_I]]
+;
+entry:
+ %cmp.i = icmp eq ptr %val1, null
+ br i1 %cmp.i, label %_Z9stringlenPKs.exit, label %while.cond.i
+
+while.cond.i:
+ %a.pn.i = phi ptr [ %val1, %entry ], [ %test.0.i, %while.cond.i ]
+ %test.0.i = getelementptr inbounds i8, ptr %a.pn.i, i64 1
+ %0 = load i8, ptr %test.0.i, align 2
+ %cmp3.not.i = icmp eq i8 %0, 0
+ br i1 %cmp3.not.i, label %while.end.i, label %while.cond.i
+
+while.end.i:
+ %sub.ptr.lhs.cast.i = ptrtoint ptr %test.0.i to i64
+ %sub.ptr.rhs.cast.i = ptrtoint ptr %val1 to i64
+ %sub.ptr.sub.i = sub i64 %sub.ptr.lhs.cast.i, %sub.ptr.rhs.cast.i
+ br label %_Z9stringlenPKs.exit
+
+_Z9stringlenPKs.exit:
+ %retval.0.i = phi i64 [ %sub.ptr.sub.i, %while.end.i ], [ 0, %entry ]
+ %bool = icmp eq i64 %retval.0.i, 0
+ ret i1 %bool
+}
+
+define i1 @recursiveGEP_withPtr_phisub1_SubOperandsCommuted(ptr noundef %val1) {
+; CHECK-LABEL: @recursiveGEP_withPtr_phisub1_SubOperandsCommuted(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp eq ptr [[VAL1:%.*]], null
+; CHECK-NEXT: br i1 [[CMP_I]], label [[_Z9STRINGLENPKS_EXIT:%.*]], label [[WHILE_COND_I:%.*]]
+; CHECK: while.cond.i:
+; CHECK-NEXT: [[A_PN_I:%.*]] = phi ptr [ [[TEST_0_I:%.*]], [[WHILE_COND_I]] ], [ [[VAL1]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TEST_0_I]] = getelementptr inbounds i8, ptr [[A_PN_I]], i64 1
+; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[TEST_0_I]], align 2
+; CHECK-NEXT: [[CMP3_NOT_I:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[CMP3_NOT_I]], label [[WHILE_END_I:%.*]], label [[WHILE_COND_I]]
+; CHECK: while.end.i:
+; CHECK-NEXT: br label [[_Z9STRINGLENPKS_EXIT]]
+; CHECK: _Z9stringlenPKs.exit:
+; CHECK-NEXT: ret i1 [[CMP_I]]
+;
+entry:
+ %cmp.i = icmp eq ptr %val1, null
+ br i1 %cmp.i, label %_Z9stringlenPKs.exit, label %while.cond.i
+
+while.cond.i:
+ %a.pn.i = phi ptr [ %test.0.i, %while.cond.i ], [ %val1, %entry ]
+ %test.0.i = getelementptr inbounds i8, ptr %a.pn.i, i64 1
+ %0 = load i8, ptr %test.0.i, align 2
+ %cmp3.not.i = icmp eq i8 %0, 0
+ br i1 %cmp3.not.i, label %while.end.i, label %while.cond.i
+
+while.end.i:
+ %sub.ptr.lhs.cast.i = ptrtoint ptr %test.0.i to i64
+ %sub.ptr.rhs.cast.i = ptrtoint ptr %val1 to i64
+ %sub.ptr.sub.i = sub i64 %sub.ptr.rhs.cast.i, %sub.ptr.lhs.cast.i
+ br label %_Z9stringlenPKs.exit
+
+_Z9stringlenPKs.exit:
+ %retval.0.i = phi i64 [ %sub.ptr.sub.i, %while.end.i ], [ 0, %entry ]
+ %bool = icmp eq i64 %retval.0.i, 0
+ ret i1 %bool
+}
+
+define i1 @recursiveGEP_withPtr_phisub2(ptr noundef %val1) {
+; CHECK-LABEL: @recursiveGEP_withPtr_phisub2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp eq ptr [[VAL1:%.*]], null
+; CHECK-NEXT: br i1 [[CMP_I]], label [[_Z9STRINGLENPKS_EXIT:%.*]], label [[WHILE_COND_I:%.*]]
+; CHECK: while.cond.i:
+; CHECK-NEXT: [[A_PN_I:%.*]] = phi ptr [ [[TEST_0_I:%.*]], [[WHILE_COND_I]] ], [ [[VAL1]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TEST_0_I]] = getelementptr inbounds i8, ptr [[A_PN_I]], i64 -1
+; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[TEST_0_I]], align 2
+; CHECK-NEXT: [[CMP3_NOT_I:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[CMP3_NOT_I]], label [[WHILE_END_I:%.*]], label [[WHILE_COND_I]]
+; CHECK: while.end.i:
+; CHECK-NEXT: br label [[_Z9STRINGLENPKS_EXIT]]
+; CHECK: _Z9stringlenPKs.exit:
+; CHECK-NEXT: ret i1 [[CMP_I]]
+;
+entry:
+ %cmp.i = icmp eq ptr %val1, null
+ br i1 %cmp.i, label %_Z9stringlenPKs.exit, label %while.cond.i
+
+while.cond.i:
+ %a.pn.i = phi ptr [ %test.0.i, %while.cond.i ], [ %val1, %entry ]
+ %test.0.i = getelementptr inbounds i8, ptr %a.pn.i, i64 -1
+ %0 = load i8, ptr %test.0.i, align 2
+ %cmp3.not.i = icmp eq i8 %0, 0
+ br i1 %cmp3.not.i, label %while.end.i, label %while.cond.i
+
+while.end.i:
+ %sub.ptr.lhs.cast.i = ptrtoint ptr %test.0.i to i64
+ %sub.ptr.rhs.cast.i = ptrtoint ptr %val1 to i64
+ %sub.ptr.sub.i = sub i64 %sub.ptr.lhs.cast.i, %sub.ptr.rhs.cast.i
+ br label %_Z9stringlenPKs.exit
+
+_Z9stringlenPKs.exit:
+ %retval.0.i = phi i64 [ %sub.ptr.sub.i, %while.end.i ], [ 0, %entry ]
+ %bool = icmp eq i64 %retval.0.i, 0
+ ret i1 %bool
+}
+
+define i1 @recursiveGEP_withPtr_phisub3(ptr noundef %val1) {
+; CHECK-LABEL: @recursiveGEP_withPtr_phisub3(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TEST_VAL1:%.*]] = getelementptr inbounds i8, ptr [[VAL1:%.*]], i64 7
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp eq ptr [[VAL1]], null
+; CHECK-NEXT: br i1 [[CMP_I]], label [[_Z9STRINGLENPKS_EXIT:%.*]], label [[WHILE_COND_I:%.*]]
+; CHECK: while.cond.i:
+; CHECK-NEXT: [[A_PN_I:%.*]] = phi ptr [ [[TEST_0_I:%.*]], [[WHILE_COND_I]] ], [ [[TEST_VAL1]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TEST_0_I]] = getelementptr inbounds i8, ptr [[A_PN_I]], i64 1
+; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[TEST_0_I]], align 2
+; CHECK-NEXT: [[CMP3_NOT_I:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[CMP3_NOT_I]], label [[WHILE_END_I:%.*]], label [[WHILE_COND_I]]
+; CHECK: while.end.i:
+; CHECK-NEXT: br label [[_Z9STRINGLENPKS_EXIT]]
+; CHECK: _Z9stringlenPKs.exit:
+; CHECK-NEXT: ret i1 [[CMP_I]]
+;
+entry:
+ %test.val1 = getelementptr inbounds i8, ptr %val1, i64 7
+ %cmp.i = icmp eq ptr %val1, null
+ br i1 %cmp.i, label %_Z9stringlenPKs.exit, label %while.cond.i
+
+while.cond.i:
+ %a.pn.i = phi ptr [ %test.0.i, %while.cond.i ], [ %test.val1, %entry ]
+ %test.0.i = getelementptr inbounds i8, ptr %a.pn.i, i64 1
+ %0 = load i8, ptr %test.0.i, align 2
+ %cmp3.not.i = icmp eq i8 %0, 0
+ br i1 %cmp3.not.i, label %while.end.i, label %while.cond.i
+
+while.end.i:
+ %sub.ptr.lhs.cast.i = ptrtoint ptr %test.0.i to i64
+ %1 = getelementptr inbounds i8, ptr %val1, i64 5
+ %sub.ptr.rhs.cast.i = ptrtoint ptr %1 to i64
+ %sub.ptr.sub.i = sub i64 %sub.ptr.lhs.cast.i, %sub.ptr.rhs.cast.i
+ br label %_Z9stringlenPKs.exit
+
+_Z9stringlenPKs.exit:
+ %retval.0.i = phi i64 [ %sub.ptr.sub.i, %while.end.i ], [ 0, %entry ]
+ %bool = icmp eq i64 %retval.0.i, 0
+ ret i1 %bool
+}
+
+define i1 @recursiveGEP_withPtr_phisub1_notKnownNonEqual1(ptr noundef %val1, i64 %val2) {
+; CHECK-LABEL: @recursiveGEP_withPtr_phisub1_notKnownNonEqual1(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp eq ptr [[VAL1:%.*]], null
+; CHECK-NEXT: br i1 [[CMP_I]], label [[_Z9STRINGLENPKS_EXIT:%.*]], label [[WHILE_COND_I:%.*]]
+; CHECK: while.cond.i:
+; CHECK-NEXT: [[A_PN_I:%.*]] = phi ptr [ [[TEST_0_I:%.*]], [[WHILE_COND_I]] ], [ [[VAL1]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TEST_0_I]] = getelementptr inbounds i8, ptr [[A_PN_I]], i64 1
+; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[TEST_0_I]], align 2
+; CHECK-NEXT: [[CMP3_NOT_I:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[CMP3_NOT_I]], label [[WHILE_END_I:%.*]], label [[WHILE_COND_I]]
+; CHECK: while.end.i:
+; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i8, ptr [[VAL1]], i64 [[VAL2:%.*]]
+; CHECK-NEXT: [[TMP2:%.*]] = icmp eq ptr [[TEST_0_I]], [[TMP1]]
+; CHECK-NEXT: br label [[_Z9STRINGLENPKS_EXIT]]
+; CHECK: _Z9stringlenPKs.exit:
+; CHECK-NEXT: [[RETVAL_0_I:%.*]] = phi i1 [ [[TMP2]], [[WHILE_END_I]] ], [ true, [[ENTRY]] ]
+; CHECK-NEXT: ret i1 [[RETVAL_0_I]]
+;
+entry:
+ %cmp.i = icmp eq ptr %val1, null
+ br i1 %cmp.i, label %_Z9stringlenPKs.exit, label %while.cond.i
+
+while.cond.i:
+ %a.pn.i = phi ptr [ %test.0.i, %while.cond.i ], [ %val1, %entry ]
+ %test.0.i = getelementptr inbounds i8, ptr %a.pn.i, i64 1
+ %0 = load i8, ptr %test.0.i, align 2
+ %cmp3.not.i = icmp eq i8 %0, 0
+ br i1 %cmp3.not.i, label %while.end.i, label %while.cond.i
+
+while.end.i:
+ %sub.ptr.lhs.cast.i = ptrtoint ptr %test.0.i to i64
+ %1 = getelementptr inbounds i8, ptr %val1, i64 %val2
+ %sub.ptr.rhs.cast.i = ptrtoint ptr %1 to i64
+ %sub.ptr.sub.i = sub i64 %sub.ptr.lhs.cast.i, %sub.ptr.rhs.cast.i
+ br label %_Z9stringlenPKs.exit
+
+_Z9stringlenPKs.exit:
+ %retval.0.i = phi i64 [ %sub.ptr.sub.i, %while.end.i ], [ 0, %entry ]
+ %bool = icmp eq i64 %retval.0.i, 0
+ ret i1 %bool
+}
+
+define i1 @recursiveGEP_withPtr_phisub1_notKnownNonEqual2(ptr noundef %val1) {
+; CHECK-LABEL: @recursiveGEP_withPtr_phisub1_notKnownNonEqual2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TEST_VAL1:%.*]] = getelementptr inbounds i8, ptr [[VAL1:%.*]], i64 -1
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp eq ptr [[VAL1]], null
+; CHECK-NEXT: br i1 [[CMP_I]], label [[_Z9STRINGLENPKS_EXIT:%.*]], label [[WHILE_COND_I:%.*]]
+; CHECK: while.cond.i:
+; CHECK-NEXT: [[A_PN_I:%.*]] = phi ptr [ [[TEST_0_I:%.*]], [[WHILE_COND_I]] ], [ [[TEST_VAL1]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TEST_0_I]] = getelementptr inbounds i8, ptr [[A_PN_I]], i64 1
+; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[TEST_0_I]], align 2
+; CHECK-NEXT: [[CMP3_NOT_I:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[CMP3_NOT_I]], label [[WHILE_END_I:%.*]], label [[WHILE_COND_I]]
+; CHECK: while.end.i:
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq ptr [[TEST_0_I]], [[VAL1]]
+; CHECK-NEXT: br label [[_Z9STRINGLENPKS_EXIT]]
+; CHECK: _Z9stringlenPKs.exit:
+; CHECK-NEXT: [[RETVAL_0_I:%.*]] = phi i1 [ [[TMP1]], [[WHILE_END_I]] ], [ true, [[ENTRY]] ]
+; CHECK-NEXT: ret i1 [[RETVAL_0_I]]
+;
+entry:
+ %test.val1 = getelementptr inbounds i8, ptr %val1, i64 -1
+ %cmp.i = icmp eq ptr %val1, null
+ br i1 %cmp.i, label %_Z9stringlenPKs.exit, label %while.cond.i
+
+while.cond.i:
+ %a.pn.i = phi ptr [ %test.0.i, %while.cond.i ], [ %test.val1, %entry ]
+ %test.0.i = getelementptr inbounds i8, ptr %a.pn.i, i64 1
+ %0 = load i8, ptr %test.0.i, align 2
+ %cmp3.not.i = icmp eq i8 %0, 0
+ br i1 %cmp3.not.i, label %while.end.i, label %while.cond.i
+
+while.end.i:
+ %sub.ptr.lhs.cast.i = ptrtoint ptr %test.0.i to i64
+ %sub.ptr.rhs.cast.i = ptrtoint ptr %val1 to i64
+ %sub.ptr.sub.i = sub i64 %sub.ptr.lhs.cast.i, %sub.ptr.rhs.cast.i
+ br label %_Z9stringlenPKs.exit
+
+_Z9stringlenPKs.exit:
+ %retval.0.i = phi i64 [ %sub.ptr.sub.i, %while.end.i ], [ 0, %entry ]
+ %bool = icmp eq i64 %retval.0.i, 0
+ ret i1 %bool
+}
+
+define i1 @recursiveGEP_withPtr_phisub1_notKnownNonEqual3(ptr noundef %val1) {
+; CHECK-LABEL: @recursiveGEP_withPtr_phisub1_notKnownNonEqual3(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TEST_VAL1:%.*]] = getelementptr inbounds i8, ptr [[VAL1:%.*]], i64 5
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp eq ptr [[VAL1]], null
+; CHECK-NEXT: br i1 [[CMP_I]], label [[_Z9STRINGLENPKS_EXIT:%.*]], label [[WHILE_COND_I:%.*]]
+; CHECK: while.cond.i:
+; CHECK-NEXT: [[A_PN_I:%.*]] = phi ptr [ [[TEST_0_I:%.*]], [[WHILE_COND_I]] ], [ [[TEST_VAL1]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TEST_0_I]] = getelementptr inbounds i8, ptr [[A_PN_I]], i64 -1
+; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[TEST_0_I]], align 2
+; CHECK-NEXT: [[CMP3_NOT_I:%.*]] = icmp eq i8 [[TMP0]], 0
+; CHECK-NEXT: br i1 [[CMP3_NOT_I]], label [[WHILE_END_I:%.*]], label [[WHILE_COND_I]]
+; CHECK: while.end.i:
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq ptr [[TEST_0_I]], [[VAL1]]
+; CHECK-NEXT: br label [[_Z9STRINGLENPKS_EXIT]]
+; CHECK: _Z9stringlenPKs.exit:
+; CHECK-NEXT: [[RETVAL_0_I:%.*]] = phi i1 [ [[TMP1]], [[WHILE_END_I]] ], [ true, [[ENTRY]] ]
+; CHECK-NEXT: ret i1 [[RETVAL_0_I]]
+;
+entry:
+ %test.val1 = getelementptr inbounds i8, ptr %val1, i64 5
+ %cmp.i = icmp eq ptr %val1, null
+ br i1 %cmp.i, label %_Z9stringlenPKs.exit, label %while.cond.i
+
+while.cond...
[truncated]
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goldsteinn
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goldsteinn
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goldsteinn
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nikic
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Ping. Let me know if there are any other review comments. Thanks. |
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davemgreen
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david-arm
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| ret i1 %bool | ||
| } | ||
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| define i1 @recursiveGEP_withPtrSub_noninbound2(ptr noundef %val1) { |
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Can you add a TODO here for potential future work? In theory even without the inbounds flag we know that %test.0.i can never equal %val1 because we add 0x100000001 to %test.0.i in each iteration. Even if it wraps in the address space the closest it gets to %val1 is %val1 + 1, hence %sub.ptr.sub.i will never be 0.
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That's the point of view I had as well. If the base pointer matches, anything that suggests an increment/decrement(irrespective of inbounds flag) should still be inequal.
@nikic I took from your suggestion that it is better to handle inbound cases for now. But if there is anything else to it do suggest.
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The only issue here could be the need to handle exactly the scenario where index is a value(positive/negative) equivalent to 0.
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For non-inbounds GEPs, whether it can be equal depends on the precise relation of the start, step and limit. You basically have the question whether Step * N == Limit - Start over the ring Z/(2^BW) has a solution. This question does have a fairly simple answer, but I don't think you should implement handling for this without cause.
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Thanks. I have added more test to showcase that this is being handled. Only exception to this is when exactly the same pointer is used for Start and Limit. Alternatively this can be handled by early check on Start/Limit being a non-inbound GEP.
llvm/lib/Analysis/ValueTracking.cpp
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| // Check if A is a Recursive GEP in one of the incoming values. | ||
| if (PN->getIncomingValue(i) == A && GEPA->getNumIndices() == 1 && | ||
| isa<Constant>(GEPA->idx_begin())) { | ||
| Step = PN->getIncomingValue(i); |
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I think the word Step here is a bit misleading, because it implies it's the difference between two values. However, it's really the updated ptr value for the next iteration. How about NextStep or NextVal?
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I agree however this seems to be commonly used for these recurring loops. Have kept it the same for now.
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Have added tests to show more non-inbounds scenario. If there are any further comments please suggest. Thanks. |
david-arm
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| ret i1 %bool | ||
| } | ||
|
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| define i1 @recursiveGEP_withPtrSub_noninbound_StepLimit(ptr noundef %val1) { |
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I'm not sure what StepLimit means here to be honest. Also, I'm not sure what value this adds over @recursiveGEP_withPtrSub_noninbound_Step1 given both are non-inbounds GEPs. Is the idea that in future you think we can add support for one of these non-inbounds GEP cases? If so, perhaps worth adding comments on the tests you think we could support.
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It is to indicate which ones in the test are non-inbounds. Have added necessary comments.
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Handled the same. Thanks |
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llvm/lib/Analysis/ValueTracking.cpp
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| return (Start == B && | ||
| ((StartOffset.sge(OffsetB) && StepOffset.isStrictlyPositive()) || | ||
| (StartOffset.sle(OffsetB) && StepOffset.isNegative()))); |
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Suggested change
| return (Start == B && | |
| ((StartOffset.sge(OffsetB) && StepOffset.isStrictlyPositive()) || | |
| (StartOffset.sle(OffsetB) && StepOffset.isNegative()))); | |
| return Start == B && | |
| ((StartOffset.sge(OffsetB) && StepOffset.isStrictlyPositive()) || | |
| (StartOffset.sle(OffsetB) && StepOffset.isNegative())); |
|
|
||
| ;Illustrate if 2 pointers are non-equal when one of them is a recursive GEP. | ||
| ;Cases which folds to a canonical icmp(ptr1, ptr2) | ||
| define i1 @recursiveGEP_withPtrSub1(ptr noundef %val1) { |
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Drop all the noundefs (assuming they're not relevant).
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Handles canonical icmp eq(ptr1, ptr2) -> where ptr1/ptr2 is a recursive GEP.
Can helps scenarios where InstCombineCompares folds icmp eq(sub(ptr2int, ptr2int), 0) -> icmp eq(ptr1, ptr2)
and
icmp eq(phi(sub(ptr2int, ptr2int), ...)) -> phi i1 (icmp eq(sub(ptr2int, ptr2int), 0), ....)