[llvm] 6ea4775 - Revert 57dd4b0 "[ValueTracking] Allow context-sensitive nullness check for non-pointers"
Hans Wennborg via llvm-commits
llvm-commits at lists.llvm.org
Wed Nov 13 03:22:11 PST 2019
Author: Hans Wennborg
Date: 2019-11-13T12:19:02+01:00
New Revision: 6ea47759008526dc11f5064b266de95c61915581
URL: https://github.com/llvm/llvm-project/commit/6ea47759008526dc11f5064b266de95c61915581
DIFF: https://github.com/llvm/llvm-project/commit/6ea47759008526dc11f5064b266de95c61915581.diff
LOG: Revert 57dd4b0 "[ValueTracking] Allow context-sensitive nullness check for non-pointers"
This caused miscompiles of Chromium (https://crbug.com/1023818). The reduced
repro is small enough to fit here:
$ cat /tmp/a.c
unsigned char f(unsigned char *p) {
unsigned char result = 0;
for (int shift = 0; shift < 1; ++shift)
result |= p[0] << (shift * 8);
return result;
}
$ bin/clang -O2 -S -o - /tmp/a.c | grep -A4 f:
f: # @f
.cfi_startproc
# %bb.0: # %entry
xorl %eax, %eax
retq
That's nicely optimized, but I don't think it's the right result :-)
> Same as D60846 but with a fix for the problem encountered there which
> was a missing context adjustment in the handling of PHI nodes.
>
> The test that caused D60846 to be reverted was added in e15ab8f277c7.
>
> Reviewers: nikic, nlopes, mkazantsev,spatel, dlrobertson, uabelho, hakzsam
>
> Subscribers: hiraditya, bollu, llvm-commits
>
> Tags: #llvm
>
> Differential Revision: https://reviews.llvm.org/D69571
This reverts commit 57dd4b03e4806bbb4760ab6150940150d884df20.
Added:
Modified:
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/lib/Analysis/ValueTracking.cpp
llvm/test/Transforms/FunctionAttrs/nonnull.ll
llvm/test/Transforms/InstCombine/known-non-zero.ll
llvm/test/Transforms/InstSimplify/known-non-zero.ll
llvm/test/Transforms/LICM/hoist-mustexec.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 3ef8f9b00509..d997acb365c4 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -543,16 +543,10 @@ static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS,
// Evaluate the BinOp on the incoming phi values.
Value *CommonValue = nullptr;
- for (unsigned u = 0, e = PI->getNumIncomingValues(); u < e; ++u) {
- Value *Incoming = PI->getIncomingValue(u);
- Instruction *InTI = PI->getIncomingBlock(u)->getTerminator();
+ for (Value *Incoming : PI->incoming_values()) {
// If the incoming value is the phi node itself, it can safely be skipped.
if (Incoming == PI) continue;
- // Change the context instruction to the "edge" that flows into the phi.
- // This is important because that is where incoming is actually "evaluated"
- // even though it is used later somewhere else.
- Value *V = SimplifyCmpInst(Pred, Incoming, RHS, Q.getWithInstruction(InTI),
- MaxRecurse);
+ Value *V = SimplifyCmpInst(Pred, Incoming, RHS, Q, MaxRecurse);
// If the operation failed to simplify, or simplified to a
diff erent value
// to previously, then give up.
if (!V || (CommonValue && V != CommonValue))
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index b26c6294dce1..f03a4a6eee45 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1902,8 +1902,8 @@ static bool isGEPKnownNonNull(const GEPOperator *GEP, unsigned Depth,
static bool isKnownNonNullFromDominatingCondition(const Value *V,
const Instruction *CtxI,
const DominatorTree *DT) {
- if (isa<Constant>(V))
- return false;
+ assert(V->getType()->isPointerTy() && "V must be pointer type");
+ assert(!isa<ConstantData>(V) && "Did not expect ConstantPointerNull");
if (!CtxI || !DT)
return false;
@@ -2078,11 +2078,12 @@ bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q) {
}
}
- if (isKnownNonNullFromDominatingCondition(V, Q.CxtI, Q.DT))
- return true;
// Check for recursive pointer simplifications.
if (V->getType()->isPointerTy()) {
+ if (isKnownNonNullFromDominatingCondition(V, Q.CxtI, Q.DT))
+ return true;
+
// Look through bitcast operations, GEPs, and int2ptr instructions as they
// do not alter the value, or at least not the nullness property of the
// value, e.g., int2ptr is allowed to zero/sign extend the value.
diff --git a/llvm/test/Transforms/FunctionAttrs/nonnull.ll b/llvm/test/Transforms/FunctionAttrs/nonnull.ll
index acdda1df0ae1..42923cee7708 100644
--- a/llvm/test/Transforms/FunctionAttrs/nonnull.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nonnull.ll
@@ -873,7 +873,7 @@ define void @PR43833_simple(i32* %0, i32 %1) {
; ATTRIBUTOR_NPM-NEXT: ret void
; ATTRIBUTOR_NPM: 8:
; ATTRIBUTOR_NPM-NEXT: [[TMP9:%.*]] = phi i32 [ 1, [[TMP4]] ], [ [[TMP10:%.*]], [[TMP8]] ]
-; ATTRIBUTOR_NPM-NEXT: tail call void @sink(i32* nonnull [[TMP6]])
+; ATTRIBUTOR_NPM-NEXT: tail call void @sink(i32* [[TMP6]])
; ATTRIBUTOR_NPM-NEXT: [[TMP10]] = add nuw nsw i32 [[TMP9]], 1
; ATTRIBUTOR_NPM-NEXT: [[TMP11:%.*]] = icmp eq i32 [[TMP10]], [[TMP1]]
; ATTRIBUTOR_NPM-NEXT: br i1 [[TMP11]], label [[TMP7]], label [[TMP8]]
diff --git a/llvm/test/Transforms/InstCombine/known-non-zero.ll b/llvm/test/Transforms/InstCombine/known-non-zero.ll
index 5467db556632..57980e0890c2 100644
--- a/llvm/test/Transforms/InstCombine/known-non-zero.ll
+++ b/llvm/test/Transforms/InstCombine/known-non-zero.ll
@@ -13,7 +13,7 @@ define i32 @test0(i64 %x) {
; CHECK-NEXT: [[C:%.*]] = icmp eq i64 [[X:%.*]], 0
; CHECK-NEXT: br i1 [[C]], label [[EXIT:%.*]], label [[NON_ZERO:%.*]]
; CHECK: non_zero:
-; CHECK-NEXT: [[CTZ:%.*]] = call i64 @llvm.cttz.i64(i64 [[X]], i1 true), !range !0
+; CHECK-NEXT: [[CTZ:%.*]] = call i64 @llvm.cttz.i64(i64 [[X]], i1 false), !range !0
; CHECK-NEXT: [[CTZ32:%.*]] = trunc i64 [[CTZ]] to i32
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
@@ -40,7 +40,7 @@ define i32 @test1(i64 %x) {
; CHECK-NEXT: [[C:%.*]] = icmp eq i64 [[X:%.*]], 0
; CHECK-NEXT: br i1 [[C]], label [[EXIT:%.*]], label [[NON_ZERO:%.*]]
; CHECK: non_zero:
-; CHECK-NEXT: [[CTZ:%.*]] = call i64 @llvm.ctlz.i64(i64 [[X]], i1 true), !range !0
+; CHECK-NEXT: [[CTZ:%.*]] = call i64 @llvm.ctlz.i64(i64 [[X]], i1 false), !range !0
; CHECK-NEXT: [[CTZ32:%.*]] = trunc i64 [[CTZ]] to i32
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
diff --git a/llvm/test/Transforms/InstSimplify/known-non-zero.ll b/llvm/test/Transforms/InstSimplify/known-non-zero.ll
index 1a985ede9a43..7e819e82b907 100644
--- a/llvm/test/Transforms/InstSimplify/known-non-zero.ll
+++ b/llvm/test/Transforms/InstSimplify/known-non-zero.ll
@@ -7,7 +7,8 @@ define i64 @test0(i64 %x) {
; CHECK-NEXT: [[A:%.*]] = icmp eq i64 [[X:%.*]], 0
; CHECK-NEXT: br i1 [[A]], label [[EXIT:%.*]], label [[NON_ZERO:%.*]]
; CHECK: non_zero:
-; CHECK-NEXT: br i1 false, label [[UNREACHABLE:%.*]], label [[EXIT]]
+; CHECK-NEXT: [[B:%.*]] = icmp eq i64 [[X]], 0
+; CHECK-NEXT: br i1 [[B]], label [[UNREACHABLE:%.*]], label [[EXIT]]
; CHECK: unreachable:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
@@ -36,7 +37,8 @@ define i64 @test1(i64 %x) {
; CHECK-NEXT: [[A:%.*]] = icmp eq i64 [[X:%.*]], 0
; CHECK-NEXT: br i1 [[A]], label [[EXIT:%.*]], label [[NON_ZERO:%.*]]
; CHECK: non_zero:
-; CHECK-NEXT: br i1 true, label [[EXIT]], label [[UNREACHABLE:%.*]]
+; CHECK-NEXT: [[B:%.*]] = icmp ugt i64 [[X]], 0
+; CHECK-NEXT: br i1 [[B]], label [[EXIT]], label [[UNREACHABLE:%.*]]
; CHECK: unreachable:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
@@ -71,9 +73,11 @@ define i1 @test2(i64 %x, i1 %y) {
; CHECK: two:
; CHECK-NEXT: br label [[MAINBLOCK]]
; CHECK: mainblock:
+; CHECK-NEXT: [[P:%.*]] = phi i64 [ [[X]], [[ONE]] ], [ 42, [[TWO]] ]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[P]], 0
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
-; CHECK-NEXT: [[RES:%.*]] = phi i1 [ false, [[MAINBLOCK]] ], [ true, [[START:%.*]] ]
+; CHECK-NEXT: [[RES:%.*]] = phi i1 [ [[CMP]], [[MAINBLOCK]] ], [ true, [[START:%.*]] ]
; CHECK-NEXT: ret i1 [[RES]]
;
start:
diff --git a/llvm/test/Transforms/LICM/hoist-mustexec.ll b/llvm/test/Transforms/LICM/hoist-mustexec.ll
index 59184eb542cf..521d35296572 100644
--- a/llvm/test/Transforms/LICM/hoist-mustexec.ll
+++ b/llvm/test/Transforms/LICM/hoist-mustexec.ll
@@ -129,6 +129,8 @@ fail:
}
; requires fact length is non-zero
+; TODO: IsKnownNonNullFromDominatingConditions is currently only be done for
+; pointers; should handle integers too
define i32 @test4(i32* noalias nocapture readonly %a) nounwind uwtable {
; CHECK-LABEL: @test4(
; CHECK-NEXT: entry:
@@ -136,7 +138,6 @@ define i32 @test4(i32* noalias nocapture readonly %a) nounwind uwtable {
; CHECK-NEXT: [[IS_ZERO:%.*]] = icmp eq i32 [[LEN]], 0
; CHECK-NEXT: br i1 [[IS_ZERO]], label [[FAIL:%.*]], label [[PREHEADER:%.*]]
; CHECK: preheader:
-; CHECK-NEXT: [[I1:%.*]] = load i32, i32* [[A]], align 4
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[PREHEADER]] ], [ [[INC:%.*]], [[CONTINUE:%.*]] ]
@@ -144,6 +145,7 @@ define i32 @test4(i32* noalias nocapture readonly %a) nounwind uwtable {
; CHECK-NEXT: [[R_CHK:%.*]] = icmp ult i32 [[IV]], [[LEN]]
; CHECK-NEXT: br i1 [[R_CHK]], label [[CONTINUE]], label [[FAIL_LOOPEXIT:%.*]]
; CHECK: continue:
+; CHECK-NEXT: [[I1:%.*]] = load i32, i32* [[A]], align 4
; CHECK-NEXT: [[ADD]] = add nsw i32 [[I1]], [[ACC]]
; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp eq i32 [[INC]], 1000
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