[llvm] [AssumeBundles] Dereferenceable used in bundle only apply at assume. (PR #126117)
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 6 12:47:40 PST 2025
https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/126117
>From efda984ec68d2704ebda8bd43e399018207390f7 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Thu, 6 Feb 2025 19:27:29 +0000
Subject: [PATCH] [AssumeBundles] Dereferenceable used in bundle only apply at
assume.
---
llvm/docs/LangRef.rst | 6 +-
llvm/lib/Analysis/Loads.cpp | 4 +-
llvm/lib/Analysis/ValueTracking.cpp | 2 +-
.../ValueTracking/assume-queries-counter.ll | 2 +-
llvm/test/Analysis/ValueTracking/assume.ll | 4 +-
.../LICM/hoist-speculatable-load.ll | 56 ++++++++++++++-
.../SimplifyCFG/speculate-derefable-load.ll | 68 +++++++++++++++++--
7 files changed, 129 insertions(+), 13 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 8891aedcb58e552..f4d6affab8f9c3e 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1474,7 +1474,11 @@ Currently, only the following parameter attributes are defined:
``null_pointer_is_valid`` function attribute is present.
``n`` should be a positive number. The pointer should be well defined,
otherwise it is undefined behavior. This means ``dereferenceable(<n>)``
- implies ``noundef``.
+ implies ``noundef``. When ``dereferenceable(<n>)`` is used in an
+ :ref:`assume operand bundls <assume_opbundles>`, the pointer is only
+ guaranteed to be dereferenceable at the point of the assumption and
+ may not be dereferenceable at later pointers, e.g. because it could have
+ been freed.
``dereferenceable_or_null(<n>)``
This indicates that the parameter or return value isn't both
diff --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp
index 733a7988e5a730a..91ae944d2e68366 100644
--- a/llvm/lib/Analysis/Loads.cpp
+++ b/llvm/lib/Analysis/Loads.cpp
@@ -26,8 +26,6 @@
using namespace llvm;
-extern cl::opt<bool> UseDerefAtPointSemantics;
-
static bool isAligned(const Value *Base, Align Alignment,
const DataLayout &DL) {
return Base->getPointerAlignment(DL) >= Alignment;
@@ -171,7 +169,7 @@ static bool isDereferenceableAndAlignedPointer(
Size, DL, CtxI, AC, DT, TLI,
Visited, MaxDepth);
- if (CtxI && (!UseDerefAtPointSemantics || !V->canBeFreed())) {
+ if (CtxI && !V->canBeFreed()) {
/// Look through assumes to see if both dereferencability and alignment can
/// be proven by an assume if needed.
RetainedKnowledge AlignRK;
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 6eba6c0f08c3f40..eac11ca379932ba 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -626,7 +626,7 @@ static bool isKnownNonZeroFromAssume(const Value *V, const SimplifyQuery &Q) {
*I, I->bundle_op_info_begin()[Elem.Index])) {
if (RK.WasOn == V &&
(RK.AttrKind == Attribute::NonNull ||
- (RK.AttrKind == Attribute::Dereferenceable &&
+ (RK.AttrKind == Attribute::Dereferenceable && !V->canBeFreed() &&
!NullPointerIsDefined(Q.CxtI->getFunction(),
V->getType()->getPointerAddressSpace()))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT))
diff --git a/llvm/test/Analysis/ValueTracking/assume-queries-counter.ll b/llvm/test/Analysis/ValueTracking/assume-queries-counter.ll
index a53b90b7b448ae8..0223ab8c4b677ab 100644
--- a/llvm/test/Analysis/ValueTracking/assume-queries-counter.ll
+++ b/llvm/test/Analysis/ValueTracking/assume-queries-counter.ll
@@ -47,7 +47,7 @@ define dso_local i1 @test2(ptr readonly %0) {
ret i1 %2
}
-define dso_local i32 @test4(ptr readonly %0, i1 %cond) {
+define dso_local i32 @test4(ptr readonly %0, i1 %cond) nofree nosync {
; COUNTER1-LABEL: @test4(
; COUNTER1-NEXT: call void @llvm.assume(i1 true) [ "dereferenceable"(ptr [[TMP0:%.*]], i32 4) ]
; COUNTER1-NEXT: br i1 [[COND:%.*]], label [[A:%.*]], label [[B:%.*]]
diff --git a/llvm/test/Analysis/ValueTracking/assume.ll b/llvm/test/Analysis/ValueTracking/assume.ll
index 4c4b46c41996868..298facfa3aa9d05 100644
--- a/llvm/test/Analysis/ValueTracking/assume.ll
+++ b/llvm/test/Analysis/ValueTracking/assume.ll
@@ -57,7 +57,7 @@ define dso_local i1 @test2(ptr readonly %0) {
ret i1 %2
}
-define dso_local i32 @test4(ptr readonly %0, i1 %cond) {
+define dso_local i32 @test4(ptr readonly %0, i1 %cond) nofree nosync {
; CHECK-LABEL: @test4(
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "dereferenceable"(ptr [[TMP0:%.*]], i32 4) ]
; CHECK-NEXT: br i1 [[COND:%.*]], label [[A:%.*]], label [[B:%.*]]
@@ -91,7 +91,7 @@ A:
ret i32 %6
}
-define dso_local i32 @test4a(ptr readonly %0, i1 %cond) {
+define dso_local i32 @test4a(ptr readonly %0, i1 %cond) nofree nosync {
; CHECK-LABEL: @test4a(
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "dereferenceable"(ptr [[TMP0:%.*]], i32 4), "align"(ptr [[TMP0]], i32 8) ]
; CHECK-NEXT: br i1 [[COND:%.*]], label [[A:%.*]], label [[B:%.*]]
diff --git a/llvm/test/Transforms/LICM/hoist-speculatable-load.ll b/llvm/test/Transforms/LICM/hoist-speculatable-load.ll
index 752cf3e99cbf5a6..cf43ff9913813e3 100644
--- a/llvm/test/Transforms/LICM/hoist-speculatable-load.ll
+++ b/llvm/test/Transforms/LICM/hoist-speculatable-load.ll
@@ -11,12 +11,12 @@ define void @f(i32 %ptr_i, ptr %ptr2, i1 %cond) {
; CHECK-NEXT: store i32 0, ptr [[PTR2:%.*]], align 4
; CHECK-NEXT: br label [[FOR_BODY_LR_PH]]
; CHECK: for.body.lr.ph:
-; CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[PTR]], align 4
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[I_08:%.*]] = phi i32 [ 0, [[FOR_BODY_LR_PH]] ], [ [[INC:%.*]], [[IF_END:%.*]] ]
; CHECK-NEXT: br i1 [[COND]], label [[IF_END]], label [[IF:%.*]]
; CHECK: if:
+; CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[PTR]], align 4, !invariant.load [[META0:![0-9]+]]
; CHECK-NEXT: store i32 [[TMP0]], ptr [[PTR2]], align 4
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
@@ -56,4 +56,58 @@ exit: ; preds = %if.end, %entry
ret void
}
+define void @f_nofree_nosync(i32 %ptr_i, ptr %ptr2, i1 %cond) nofree nosync {
+; CHECK-LABEL: @f_nofree_nosync(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[PTR:%.*]] = inttoptr i32 [[PTR_I:%.*]] to ptr
+; CHECK-NEXT: call void @llvm.assume(i1 true) [ "align"(ptr [[PTR]], i32 16), "dereferenceable"(ptr [[PTR]], i32 16) ]
+; CHECK-NEXT: br i1 [[COND:%.*]], label [[FOR_BODY_LR_PH:%.*]], label [[IF0:%.*]]
+; CHECK: if0:
+; CHECK-NEXT: store i32 0, ptr [[PTR2:%.*]], align 4
+; CHECK-NEXT: br label [[FOR_BODY_LR_PH]]
+; CHECK: for.body.lr.ph:
+; CHECK-NEXT: br label [[FOR_BODY:%.*]]
+; CHECK: for.body:
+; CHECK-NEXT: [[I_08:%.*]] = phi i32 [ 0, [[FOR_BODY_LR_PH]] ], [ [[INC:%.*]], [[IF_END:%.*]] ]
+; CHECK-NEXT: br i1 [[COND]], label [[IF_END]], label [[IF:%.*]]
+; CHECK: if:
+; CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[PTR]], align 4, !invariant.load [[META0]]
+; CHECK-NEXT: store i32 [[TMP0]], ptr [[PTR2]], align 4
+; CHECK-NEXT: br label [[IF_END]]
+; CHECK: if.end:
+; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[I_08]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[INC]], 2
+; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[EXIT:%.*]]
+; CHECK: exit:
+; CHECK-NEXT: ret void
+;
+entry:
+ %ptr = inttoptr i32 %ptr_i to ptr
+ call void @llvm.assume(i1 true) [ "align"(ptr %ptr, i32 16), "dereferenceable"(ptr %ptr, i32 16) ]
+ br i1 %cond, label %for.body.lr.ph, label %if0
+
+if0:
+ store i32 0, ptr %ptr2, align 4
+ br label %for.body.lr.ph
+
+for.body.lr.ph: ; preds = %entry
+ br label %for.body
+
+for.body: ; preds = %for.body.lr.ph, %if.end
+ %i.08 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %if.end ]
+ br i1 %cond, label %if.end, label %if
+
+if:
+ %0 = load i32, ptr %ptr, align 4, !invariant.load !{}
+ store i32 %0, ptr %ptr2, align 4
+ br label %if.end
+
+if.end: ; preds = %for.body
+ %inc = add nuw nsw i32 %i.08, 1
+ %cmp = icmp slt i32 %inc, 2
+ br i1 %cmp, label %for.body, label %exit
+
+exit: ; preds = %if.end, %entry
+ ret void
+}
declare void @llvm.assume(i1 noundef)
diff --git a/llvm/test/Transforms/SimplifyCFG/speculate-derefable-load.ll b/llvm/test/Transforms/SimplifyCFG/speculate-derefable-load.ll
index 0138433312ed84a..b8c999d700aa7da 100644
--- a/llvm/test/Transforms/SimplifyCFG/speculate-derefable-load.ll
+++ b/llvm/test/Transforms/SimplifyCFG/speculate-derefable-load.ll
@@ -4,10 +4,14 @@
define i64 @align_deref_align(i1 %c, ptr %p) {
; CHECK-LABEL: define i64 @align_deref_align(
; CHECK-SAME: i1 [[C:%.*]], ptr [[P:%.*]]) {
-; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "dereferenceable"(ptr [[P]], i64 8), "align"(ptr [[P]], i64 8) ]
+; CHECK-NEXT: br i1 [[C]], label %[[IF:.*]], label %[[EXIT:.*]]
+; CHECK: [[IF]]:
; CHECK-NEXT: [[V:%.*]] = load i64, ptr [[P]], align 8
-; CHECK-NEXT: [[RES:%.*]] = select i1 [[C]], i64 [[V]], i64 0
+; CHECK-NEXT: br label %[[EXIT]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: [[RES:%.*]] = phi i64 [ [[V]], %[[IF]] ], [ 0, %[[ENTRY]] ]
; CHECK-NEXT: ret i64 [[RES]]
;
entry:
@@ -23,9 +27,64 @@ exit:
ret i64 %res
}
+define i64 @align_deref_align_nofree_nosync(i1 %c, ptr %p) nofree nosync {
+; CHECK-LABEL: define i64 @align_deref_align_nofree_nosync(
+; CHECK-SAME: i1 [[C:%.*]], ptr [[P:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: call void @llvm.assume(i1 true) [ "dereferenceable"(ptr [[P]], i64 8), "align"(ptr [[P]], i64 8) ]
+; CHECK-NEXT: [[V:%.*]] = load i64, ptr [[P]], align 8
+; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 [[C]], i64 [[V]], i64 0
+; CHECK-NEXT: ret i64 [[SPEC_SELECT]]
+;
+entry:
+ call void @llvm.assume(i1 true) [ "dereferenceable"(ptr %p, i64 8), "align"(ptr %p, i64 8) ]
+ br i1 %c, label %if, label %exit
+
+if:
+ %v = load i64, ptr %p, align 8
+ br label %exit
+
+exit:
+ %res = phi i64 [ %v, %if ], [ 0, %entry ]
+ ret i64 %res
+}
+
define i64 @assume_deref_align2(i1 %c1, i32 %x, ptr %p) {
; CHECK-LABEL: define i64 @assume_deref_align2(
; CHECK-SAME: i1 [[C1:%.*]], i32 [[X:%.*]], ptr [[P:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*]]:
+; CHECK-NEXT: call void @llvm.assume(i1 true) [ "dereferenceable"(ptr [[P]], i64 8), "align"(ptr [[P]], i64 8) ]
+; CHECK-NEXT: br i1 [[C1]], label %[[IF1:.*]], label %[[EXIT:.*]]
+; CHECK: [[IF1]]:
+; CHECK-NEXT: [[C2:%.*]] = icmp ugt i32 [[X]], 10
+; CHECK-NEXT: br i1 [[C2]], label %[[IF2:.*]], label %[[EXIT]]
+; CHECK: [[IF2]]:
+; CHECK-NEXT: [[V:%.*]] = load i64, ptr [[P]], align 8
+; CHECK-NEXT: br label %[[EXIT]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: [[RES:%.*]] = phi i64 [ [[V]], %[[IF2]] ], [ 1, %[[IF1]] ], [ 0, %[[ENTRY]] ]
+; CHECK-NEXT: ret i64 [[RES]]
+;
+entry:
+ call void @llvm.assume(i1 true) [ "dereferenceable"(ptr %p, i64 8), "align"(ptr %p, i64 8) ]
+ br i1 %c1, label %if1, label %exit
+
+if1:
+ %c2 = icmp ugt i32 %x, 10
+ br i1 %c2, label %if2, label %exit
+
+if2:
+ %v = load i64, ptr %p, align 8
+ br label %exit
+
+exit:
+ %res = phi i64 [ %v, %if2 ], [ 1, %if1 ], [ 0, %entry ]
+ ret i64 %res
+}
+
+define i64 @assume_deref_align2_nofree_nosync(i1 %c1, i32 %x, ptr %p) nofree nosync {
+; CHECK-LABEL: define i64 @assume_deref_align2_nofree_nosync(
+; CHECK-SAME: i1 [[C1:%.*]], i32 [[X:%.*]], ptr [[P:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "dereferenceable"(ptr [[P]], i64 8), "align"(ptr [[P]], i64 8) ]
; CHECK-NEXT: [[C2:%.*]] = icmp ugt i32 [[X]], 10
@@ -51,9 +110,10 @@ exit:
ret i64 %res
}
-define i64 @assume_deref_align_not_dominating(i1 %c, ptr %p) {
+
+define i64 @assume_deref_align_not_dominating(i1 %c, ptr %p) nofree nosync {
; CHECK-LABEL: define i64 @assume_deref_align_not_dominating(
-; CHECK-SAME: i1 [[C:%.*]], ptr [[P:%.*]]) {
+; CHECK-SAME: i1 [[C:%.*]], ptr [[P:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: br i1 [[C]], label %[[IF:.*]], label %[[EXIT:.*]]
; CHECK: [[IF]]:
More information about the llvm-commits
mailing list