[llvm] [ValueTracking] AllowEphemerals for alignment assumptions. (PR #108632)
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 2 02:32:28 PDT 2024
https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/108632
>From aee8cb0ccbf808d675b753f541a68ad25497b6f4 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Fri, 13 Sep 2024 13:38:19 +0100
Subject: [PATCH] [ValueTracking] AllowEphemerals for alignment assumptions.
Allow AllowEphemerals in isValidAssumeForContext, as the CxtI might
be the producer of the pointer in the bundle. At the moment, align
assumptions aren't optimized away.
This allows using the assumption in the computeKnownBits call in
getConstantMultipleImpl.
We could extend the computeKnownBits API to allow callers to specify if
ephemerals are allowed, if the info from computeKnownBitsFromContext is
used to remove alignment assumptions.
---
llvm/lib/Analysis/ValueTracking.cpp | 5 +-
.../max-backedge-taken-count-guard-info.ll | 60 +++++--------------
2 files changed, 20 insertions(+), 45 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 56eb3f99b39d2c..1fe7dbb89a795d 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -821,9 +821,12 @@ void llvm::computeKnownBitsFromContext(const Value *V, KnownBits &Known,
continue;
if (RetainedKnowledge RK = getKnowledgeFromBundle(
*I, I->bundle_op_info_begin()[Elem.Index])) {
+ // Allow AllowEphemerals in isValidAssumeForContext, as the CxtI might
+ // be the producer of the pointer in the bundle. At the moment, align
+ // assumptions aren't optimized away.
if (RK.WasOn == V && RK.AttrKind == Attribute::Alignment &&
isPowerOf2_64(RK.ArgValue) &&
- isValidAssumeForContext(I, Q.CxtI, Q.DT))
+ isValidAssumeForContext(I, Q.CxtI, Q.DT, /*AllowEphemerals*/ true))
Known.Zero.setLowBits(Log2_64(RK.ArgValue));
}
continue;
diff --git a/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll b/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
index 42706df82f37cd..30c3bbfb12e5de 100644
--- a/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
+++ b/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
@@ -1709,37 +1709,23 @@ define void @ptr_induction_early_exit_eq_1_align_assumption_1(ptr %a, ptr %b, pt
; CHECK-LABEL: 'ptr_induction_early_exit_eq_1_align_assumption_1'
; CHECK-NEXT: Classifying expressions for: @ptr_induction_early_exit_eq_1_align_assumption_1
; CHECK-NEXT: %a_ = load ptr, ptr %a, align 8
-; CHECK-NEXT: --> %a_ U: full-set S: full-set
+; CHECK-NEXT: --> %a_ U: [0,-7) S: [-9223372036854775808,9223372036854775801)
; CHECK-NEXT: %b_ = load ptr, ptr %b, align 8
-; CHECK-NEXT: --> %b_ U: full-set S: full-set
+; CHECK-NEXT: --> %b_ U: [0,-7) S: [-9223372036854775808,9223372036854775801)
; CHECK-NEXT: %ptr.iv = phi ptr [ %ptr.iv.next, %loop.inc ], [ %a_, %entry ]
-; CHECK-NEXT: --> {%a_,+,8}<nuw><%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT: --> {%a_,+,8}<nuw><%loop> U: [0,-7) S: [-9223372036854775808,9223372036854775801) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %ld1 = load ptr, ptr %ptr.iv, align 8
; CHECK-NEXT: --> %ld1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %ptr.iv.next = getelementptr inbounds i8, ptr %ptr.iv, i64 8
-; CHECK-NEXT: --> {(8 + %a_),+,8}<nw><%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT: --> {(8 + %a_),+,8}<nw><%loop> U: [0,-7) S: [-9223372036854775808,9223372036854775801) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @ptr_induction_early_exit_eq_1_align_assumption_1
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
-; CHECK-NEXT: exit count for loop.inc: ***COULDNOTCOMPUTE***
-; CHECK-NEXT: predicated exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT: Predicates:
-; CHECK-NEXT: Equal predicate: (zext i3 ((trunc i64 (ptrtoint ptr %b_ to i64) to i3) + (-1 * (trunc i64 (ptrtoint ptr %a_ to i64) to i3))) to i64) == 0
-; CHECK-EMPTY:
-; CHECK-NEXT: Loop %loop: Unpredictable constant max backedge-taken count.
-; CHECK-NEXT: Loop %loop: Unpredictable symbolic max backedge-taken count.
+; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
+; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
-; CHECK-NEXT: symbolic max exit count for loop.inc: ***COULDNOTCOMPUTE***
-; CHECK-NEXT: predicated symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT: Predicates:
-; CHECK-NEXT: Equal predicate: (zext i3 ((trunc i64 (ptrtoint ptr %b_ to i64) to i3) + (-1 * (trunc i64 (ptrtoint ptr %a_ to i64) to i3))) to i64) == 0
-; CHECK-EMPTY:
-; CHECK-NEXT: Loop %loop: Predicated constant max backedge-taken count is i64 2305843009213693951
-; CHECK-NEXT: Predicates:
-; CHECK-NEXT: Equal predicate: (zext i3 ((trunc i64 (ptrtoint ptr %b_ to i64) to i3) + (-1 * (trunc i64 (ptrtoint ptr %a_ to i64) to i3))) to i64) == 0
-; CHECK-NEXT: Loop %loop: Predicated symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT: Predicates:
-; CHECK-NEXT: Equal predicate: (zext i3 ((trunc i64 (ptrtoint ptr %b_ to i64) to i3) + (-1 * (trunc i64 (ptrtoint ptr %a_ to i64) to i3))) to i64) == 0
+; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
;
entry:
%a_ = load ptr, ptr %a
@@ -1768,37 +1754,23 @@ define void @ptr_induction_early_exit_eq_1_align_assumption_2(ptr %a, ptr %b, pt
; CHECK-LABEL: 'ptr_induction_early_exit_eq_1_align_assumption_2'
; CHECK-NEXT: Classifying expressions for: @ptr_induction_early_exit_eq_1_align_assumption_2
; CHECK-NEXT: %a_ = load ptr, ptr %a, align 8
-; CHECK-NEXT: --> %a_ U: full-set S: full-set
+; CHECK-NEXT: --> %a_ U: [0,-7) S: [-9223372036854775808,9223372036854775801)
; CHECK-NEXT: %b_ = load ptr, ptr %b, align 8
-; CHECK-NEXT: --> %b_ U: full-set S: full-set
+; CHECK-NEXT: --> %b_ U: [0,-7) S: [-9223372036854775808,9223372036854775801)
; CHECK-NEXT: %ptr.iv = phi ptr [ %ptr.iv.next, %loop.inc ], [ %a_, %entry ]
-; CHECK-NEXT: --> {%a_,+,8}<nuw><%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT: --> {%a_,+,8}<nuw><%loop> U: [0,-7) S: [-9223372036854775808,9223372036854775801) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %ld1 = load ptr, ptr %ptr.iv, align 8
; CHECK-NEXT: --> %ld1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %ptr.iv.next = getelementptr inbounds i8, ptr %ptr.iv, i64 8
-; CHECK-NEXT: --> {(8 + %a_),+,8}<nw><%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT: --> {(8 + %a_),+,8}<nw><%loop> U: [0,-7) S: [-9223372036854775808,9223372036854775801) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @ptr_induction_early_exit_eq_1_align_assumption_2
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
-; CHECK-NEXT: exit count for loop.inc: ***COULDNOTCOMPUTE***
-; CHECK-NEXT: predicated exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT: Predicates:
-; CHECK-NEXT: Equal predicate: (zext i3 ((trunc i64 (ptrtoint ptr %b_ to i64) to i3) + (-1 * (trunc i64 (ptrtoint ptr %a_ to i64) to i3))) to i64) == 0
-; CHECK-EMPTY:
-; CHECK-NEXT: Loop %loop: Unpredictable constant max backedge-taken count.
-; CHECK-NEXT: Loop %loop: Unpredictable symbolic max backedge-taken count.
+; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
+; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
-; CHECK-NEXT: symbolic max exit count for loop.inc: ***COULDNOTCOMPUTE***
-; CHECK-NEXT: predicated symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT: Predicates:
-; CHECK-NEXT: Equal predicate: (zext i3 ((trunc i64 (ptrtoint ptr %b_ to i64) to i3) + (-1 * (trunc i64 (ptrtoint ptr %a_ to i64) to i3))) to i64) == 0
-; CHECK-EMPTY:
-; CHECK-NEXT: Loop %loop: Predicated constant max backedge-taken count is i64 2305843009213693951
-; CHECK-NEXT: Predicates:
-; CHECK-NEXT: Equal predicate: (zext i3 ((trunc i64 (ptrtoint ptr %b_ to i64) to i3) + (-1 * (trunc i64 (ptrtoint ptr %a_ to i64) to i3))) to i64) == 0
-; CHECK-NEXT: Loop %loop: Predicated symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT: Predicates:
-; CHECK-NEXT: Equal predicate: (zext i3 ((trunc i64 (ptrtoint ptr %b_ to i64) to i3) + (-1 * (trunc i64 (ptrtoint ptr %a_ to i64) to i3))) to i64) == 0
+; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
;
entry:
%a_ = load ptr, ptr %a
More information about the llvm-commits
mailing list