[llvm] [ValueTracking] Handle assume( trunc x to i1) (PR #118406)
Andreas Jonson via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 2 14:29:04 PST 2024
https://github.com/andjo403 created https://github.com/llvm/llvm-project/pull/118406
Handle assume( trunc x to i1) in ComputeKnownBits and KnownNonZero to avoid regressions when converting more icmp to trunc as the https://github.com/llvm/llvm-project/pull/84628 remove the canonicalization `trunc x to i1 -> icmp ne (and x, 1), 0`
part of https://github.com/llvm/llvm-project/issues/118104
>From 8e1b5acb1810d879ba5fb73677c2c98530bc6f51 Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Mon, 2 Dec 2024 22:44:07 +0100
Subject: [PATCH 1/3] [ValueTracking] Add test for assume with trunc as
argument (NFC)
---
.../Transforms/InstSimplify/assume-non-zero.ll | 14 ++++++++++++++
llvm/test/Transforms/InstSimplify/compare.ll | 15 +++++++++++++++
llvm/test/Transforms/InstSimplify/shr-nop.ll | 13 +++++++++++++
3 files changed, 42 insertions(+)
diff --git a/llvm/test/Transforms/InstSimplify/assume-non-zero.ll b/llvm/test/Transforms/InstSimplify/assume-non-zero.ll
index 9176b8101da659..22bdf374487dab 100644
--- a/llvm/test/Transforms/InstSimplify/assume-non-zero.ll
+++ b/llvm/test/Transforms/InstSimplify/assume-non-zero.ll
@@ -231,3 +231,17 @@ define i1 @nonnull17_unknown(i8 %x) {
%q = icmp ne i8 %x, 0
ret i1 %q
}
+
+define i1 @nonnull_trunc_true(i8 %x) {
+; CHECK-LABEL: @nonnull_trunc_true(
+; CHECK-NEXT: [[A:%.*]] = trunc i8 [[X:%.*]] to i1
+; CHECK-NEXT: call void @llvm.assume(i1 [[A]])
+; CHECK-NEXT: [[Q:%.*]] = icmp ne i8 [[X]], 0
+; CHECK-NEXT: ret i1 [[Q]]
+;
+ %a = trunc i8 %x to i1
+ call void @llvm.assume(i1 %a)
+ %q = icmp ne i8 %x, 0
+ ret i1 %q
+}
+
diff --git a/llvm/test/Transforms/InstSimplify/compare.ll b/llvm/test/Transforms/InstSimplify/compare.ll
index 21653d800dce2d..191e76b0532028 100644
--- a/llvm/test/Transforms/InstSimplify/compare.ll
+++ b/llvm/test/Transforms/InstSimplify/compare.ll
@@ -3424,6 +3424,21 @@ define i1 @icmp_ult_vscale_false(i8 %x, i8 %y) {
ret i1 %cmp
}
+define i1 @icmp_eq_false_by_trunc(i8 %x) {
+; CHECK-LABEL: @icmp_eq_false_by_trunc(
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[X:%.*]] to i1
+; CHECK-NEXT: [[NOT:%.*]] = xor i1 [[TRUNC]], true
+; CHECK-NEXT: call void @llvm.assume(i1 [[NOT]])
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], 1
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %trunc = trunc i8 %x to i1
+ %not = xor i1 %trunc, true
+ call void @llvm.assume(i1 %not)
+ %cmp = icmp eq i8 %x, 1
+ ret i1 %cmp
+}
+
declare i64 @llvm.vscale.i64()
; TODO: Add coverage for global aliases, link once, etc..
diff --git a/llvm/test/Transforms/InstSimplify/shr-nop.ll b/llvm/test/Transforms/InstSimplify/shr-nop.ll
index 29fe222faaae3e..4b9292aab4bb3e 100644
--- a/llvm/test/Transforms/InstSimplify/shr-nop.ll
+++ b/llvm/test/Transforms/InstSimplify/shr-nop.ll
@@ -381,6 +381,19 @@ define i32 @exact_lshr_lowbit(i32 %shiftval) {
ret i32 %shr
}
+define i8 @exact_lshr_lowbit_set_assume_trunc(i8 %x) {
+; CHECK-LABEL: @exact_lshr_lowbit_set_assume_trunc(
+; CHECK-NEXT: [[COND:%.*]] = trunc i8 [[X:%.*]] to i1
+; CHECK-NEXT: call void @llvm.assume(i1 [[COND]])
+; CHECK-NEXT: [[SHR:%.*]] = lshr exact i8 [[X]], 1
+; CHECK-NEXT: ret i8 [[SHR]]
+;
+ %cond = trunc i8 %x to i1
+ call void @llvm.assume(i1 %cond)
+ %shr = lshr exact i8 %x, 1
+ ret i8 %shr
+}
+
define i32 @exact_ashr_lowbit(i32 %shiftval) {
; CHECK-LABEL: @exact_ashr_lowbit(
; CHECK-NEXT: ret i32 7
>From 629bf1ce48a9511529d82105b972c58441c01093 Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Mon, 2 Dec 2024 23:00:12 +0100
Subject: [PATCH 2/3] [ValueTracking] Handle assume(trunc x to i1) in
knownNonZero
---
llvm/lib/Analysis/ValueTracking.cpp | 7 ++++++-
llvm/test/Transforms/Attributor/lvi-after-jumpthreading.ll | 5 +----
llvm/test/Transforms/InstSimplify/assume-non-zero.ll | 3 +--
3 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index c48068afc04816..7c4812d849fa21 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -612,11 +612,16 @@ static bool isKnownNonZeroFromAssume(const Value *V, const SimplifyQuery &Q) {
// Warning: This loop can end up being somewhat performance sensitive.
// We're running this loop for once for each value queried resulting in a
// runtime of ~O(#assumes * #values).
+ Value *Arg = I->getArgOperand(0);
+ if (match(Arg, m_TruncOrSelf(m_Specific(V))) &&
+ isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
+ return true;
+ }
Value *RHS;
CmpInst::Predicate Pred;
auto m_V = m_CombineOr(m_Specific(V), m_PtrToInt(m_Specific(V)));
- if (!match(I->getArgOperand(0), m_c_ICmp(Pred, m_V, m_Value(RHS))))
+ if (!match(Arg, m_c_ICmp(Pred, m_V, m_Value(RHS))))
continue;
if (cmpExcludesZero(Pred, RHS) && isValidAssumeForContext(I, Q.CxtI, Q.DT))
diff --git a/llvm/test/Transforms/Attributor/lvi-after-jumpthreading.ll b/llvm/test/Transforms/Attributor/lvi-after-jumpthreading.ll
index 2aa95216a66569..fd9d2e4de61ba8 100644
--- a/llvm/test/Transforms/Attributor/lvi-after-jumpthreading.ll
+++ b/llvm/test/Transforms/Attributor/lvi-after-jumpthreading.ll
@@ -130,8 +130,6 @@ exit2:
ret i32 30
}
-; FIXME: We should be able to merge cont into do.
-; FIXME: COND should be replaced with false. This will be fixed by improving LVI.
define i32 @test4(i32 %i, i1 %f, i32 %n) {
; CHECK-LABEL: define {{[^@]+}}@test4
; CHECK-SAME: (i32 [[I:%.*]], i1 [[F:%.*]], i32 [[N:%.*]]) {
@@ -148,8 +146,7 @@ define i32 @test4(i32 %i, i1 %f, i32 %n) {
; CHECK-NEXT: call void @dummy(i1 [[F]]) #[[ATTR2]]
; CHECK-NEXT: [[CONSUME:%.*]] = call i32 @exit()
; CHECK-NEXT: call void @llvm.assume(i1 noundef [[F]])
-; CHECK-NEXT: [[COND:%.*]] = icmp eq i1 [[F]], false
-; CHECK-NEXT: br i1 [[COND]], label [[EXIT]], label [[CONT:%.*]]
+; CHECK-NEXT: br label [[CONT:%.*]]
; CHECK: exit2:
; CHECK-NEXT: ret i32 30
;
diff --git a/llvm/test/Transforms/InstSimplify/assume-non-zero.ll b/llvm/test/Transforms/InstSimplify/assume-non-zero.ll
index 22bdf374487dab..331c9504f2da6f 100644
--- a/llvm/test/Transforms/InstSimplify/assume-non-zero.ll
+++ b/llvm/test/Transforms/InstSimplify/assume-non-zero.ll
@@ -236,8 +236,7 @@ define i1 @nonnull_trunc_true(i8 %x) {
; CHECK-LABEL: @nonnull_trunc_true(
; CHECK-NEXT: [[A:%.*]] = trunc i8 [[X:%.*]] to i1
; CHECK-NEXT: call void @llvm.assume(i1 [[A]])
-; CHECK-NEXT: [[Q:%.*]] = icmp ne i8 [[X]], 0
-; CHECK-NEXT: ret i1 [[Q]]
+; CHECK-NEXT: ret i1 true
;
%a = trunc i8 %x to i1
call void @llvm.assume(i1 %a)
>From a32a72175ff3f179c3d84a47e41451eca96342f9 Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Mon, 2 Dec 2024 23:04:43 +0100
Subject: [PATCH 3/3] [ValueTracking] Handle assume( trunc x to i1) in
ComputeKnownBits
---
llvm/lib/Analysis/ValueTracking.cpp | 15 +++++----------
llvm/test/Transforms/InstSimplify/compare.ll | 3 +--
llvm/test/Transforms/InstSimplify/shr-nop.ll | 3 +--
3 files changed, 7 insertions(+), 14 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 7c4812d849fa21..7b7eea027c82b9 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -814,8 +814,6 @@ void llvm::computeKnownBitsFromContext(const Value *V, KnownBits &Known,
if (!Q.AC)
return;
- unsigned BitWidth = Known.getBitWidth();
-
// Note that the patterns below need to be kept in sync with the code
// in AssumptionCache::updateAffectedValues.
@@ -849,17 +847,14 @@ void llvm::computeKnownBitsFromContext(const Value *V, KnownBits &Known,
Value *Arg = I->getArgOperand(0);
- if (Arg == V && isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
- assert(BitWidth == 1 && "assume operand is not i1?");
- (void)BitWidth;
- Known.setAllOnes();
+ if (match(Arg, m_TruncOrSelf(m_Specific(V))) &&
+ isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
+ Known.One.setBit(0);
return;
}
- if (match(Arg, m_Not(m_Specific(V))) &&
+ if (match(Arg, m_Not(m_TruncOrSelf(m_Specific(V)))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
- assert(BitWidth == 1 && "assume operand is not i1?");
- (void)BitWidth;
- Known.setAllZero();
+ Known.Zero.setBit(0);
return;
}
diff --git a/llvm/test/Transforms/InstSimplify/compare.ll b/llvm/test/Transforms/InstSimplify/compare.ll
index 191e76b0532028..a2a8fe42e7583b 100644
--- a/llvm/test/Transforms/InstSimplify/compare.ll
+++ b/llvm/test/Transforms/InstSimplify/compare.ll
@@ -3429,8 +3429,7 @@ define i1 @icmp_eq_false_by_trunc(i8 %x) {
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[X:%.*]] to i1
; CHECK-NEXT: [[NOT:%.*]] = xor i1 [[TRUNC]], true
; CHECK-NEXT: call void @llvm.assume(i1 [[NOT]])
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], 1
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 false
;
%trunc = trunc i8 %x to i1
%not = xor i1 %trunc, true
diff --git a/llvm/test/Transforms/InstSimplify/shr-nop.ll b/llvm/test/Transforms/InstSimplify/shr-nop.ll
index 4b9292aab4bb3e..b18a1c6d30e745 100644
--- a/llvm/test/Transforms/InstSimplify/shr-nop.ll
+++ b/llvm/test/Transforms/InstSimplify/shr-nop.ll
@@ -385,8 +385,7 @@ define i8 @exact_lshr_lowbit_set_assume_trunc(i8 %x) {
; CHECK-LABEL: @exact_lshr_lowbit_set_assume_trunc(
; CHECK-NEXT: [[COND:%.*]] = trunc i8 [[X:%.*]] to i1
; CHECK-NEXT: call void @llvm.assume(i1 [[COND]])
-; CHECK-NEXT: [[SHR:%.*]] = lshr exact i8 [[X]], 1
-; CHECK-NEXT: ret i8 [[SHR]]
+; CHECK-NEXT: ret i8 [[X]]
;
%cond = trunc i8 %x to i1
call void @llvm.assume(i1 %cond)
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